/* SPDX-License-Identifier: GPL-2.0-only */
/*
 * nestedsvm.c: Nested Virtualization
 * Copyright (c) 2011, Advanced Micro Devices, Inc
 *
 */

#include <asm/hvm/support.h>
#include <asm/hvm/svm.h>
#include <asm/hvm/nestedhvm.h>
#include <asm/paging.h> /* paging_mode_hap */
#include <asm/event.h> /* for local_event_delivery_(en|dis)able */
#include <asm/p2m.h> /* p2m_get_pagetable, p2m_get_nestedp2m */

#include "nestedhvm.h"
#include "svm.h"
#include "vmcb.h"

#define NSVM_ERROR_VVMCB        1
#define NSVM_ERROR_VMENTRY      2

int nestedsvm_vmcb_map(struct vcpu *v, uint64_t vmcbaddr)
{
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);

    if ( nv->nv_vvmcx != NULL && nv->nv_vvmcxaddr != vmcbaddr )
    {
        ASSERT(vvmcx_valid(v));
        hvm_unmap_guest_frame(nv->nv_vvmcx, 1);
        nv->nv_vvmcx = NULL;
        nv->nv_vvmcxaddr = INVALID_PADDR;
    }

    if ( !nv->nv_vvmcx )
    {
        bool writable;
        void *vvmcx = hvm_map_guest_frame_rw(paddr_to_pfn(vmcbaddr), 1,
                                             &writable);

        if ( !vvmcx )
            return 0;
        if ( !writable )
        {
            hvm_unmap_guest_frame(vvmcx, 1);
            return 0;
        }
        nv->nv_vvmcx = vvmcx;
        nv->nv_vvmcxaddr = vmcbaddr;
    }

    return 1;
}

/* Interface methods */
int cf_check nsvm_vcpu_initialise(struct vcpu *v)
{
    void *msrpm;
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);

    msrpm = alloc_xenheap_pages(get_order_from_bytes(MSRPM_SIZE), 0);
    svm->ns_cached_msrpm = msrpm;
    if ( msrpm == NULL )
        goto err;
    memset(msrpm, 0x0, MSRPM_SIZE);

    msrpm = alloc_xenheap_pages(get_order_from_bytes(MSRPM_SIZE), 0);
    svm->ns_merged_msrpm = msrpm;
    if ( msrpm == NULL )
        goto err;
    memset(msrpm, 0x0, MSRPM_SIZE);

    nv->nv_n2vmcx = alloc_vmcb();
    if ( nv->nv_n2vmcx == NULL )
        goto err;
    nv->nv_n2vmcx_pa = virt_to_maddr(nv->nv_n2vmcx);

    return 0;

 err:
    nsvm_vcpu_destroy(v);
    return -ENOMEM;
}

void cf_check nsvm_vcpu_destroy(struct vcpu *v)
{
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);

    /*
     * When destroying the vcpu, it may be running on behalf of l2 guest.
     * Therefore we need to switch the VMCB pointer back to the l1 vmcb,
     * in order to avoid double free of l2 vmcb and the possible memory leak
     * of l1 vmcb page.
     */
    if ( nv->nv_n1vmcx )
        v->arch.hvm.svm.vmcb = nv->nv_n1vmcx;

    if ( svm->ns_cached_msrpm )
    {
        free_xenheap_pages(svm->ns_cached_msrpm,
                           get_order_from_bytes(MSRPM_SIZE));
        svm->ns_cached_msrpm = NULL;
    }

    if ( svm->ns_merged_msrpm )
    {
        free_xenheap_pages(svm->ns_merged_msrpm,
                           get_order_from_bytes(MSRPM_SIZE));
        svm->ns_merged_msrpm = NULL;
    }

    hvm_unmap_guest_frame(nv->nv_vvmcx, 1);
    nv->nv_vvmcx = NULL;
    if ( nv->nv_n2vmcx )
    {
        free_vmcb(nv->nv_n2vmcx);
        nv->nv_n2vmcx = NULL;
        nv->nv_n2vmcx_pa = INVALID_PADDR;
    }

    svm->ns_iomap = NULL;
}

int cf_check nsvm_vcpu_reset(struct vcpu *v)
{
    struct nestedsvm *svm = &vcpu_nestedsvm(v);

    svm->ns_msr_hsavepa = INVALID_PADDR;
    svm->ns_ovvmcb_pa = INVALID_PADDR;

    svm->ns_cr_intercepts = 0;
    svm->ns_dr_intercepts = 0;
    svm->ns_exception_intercepts = 0;
    svm->ns_general1_intercepts = 0;
    svm->ns_general2_intercepts = 0;

    svm->ns_hap_enabled = 0;
    svm->ns_vmcb_guestcr3 = 0;
    svm->ns_vmcb_hostcr3 = 0;
    svm->ns_asid = 0;
    svm->ns_hostflags.bytes = 0;
    svm->ns_vmexit.exitinfo1 = 0;
    svm->ns_vmexit.exitinfo2 = 0;

    svm->ns_iomap = NULL;

    svm->ns_gif = 1;
    return 0;
}

static int nsvm_vcpu_hostsave(struct vcpu *v, unsigned int inst_len)
{
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct vmcb_struct *n1vmcb;

    n1vmcb = nv->nv_n1vmcx;
    ASSERT(n1vmcb != NULL);

    n1vmcb->rip += inst_len;

    /*
     * Save shadowed values. This ensures that the l1 guest
     * cannot override them to break out.
     */
    n1vmcb->_efer = v->arch.hvm.guest_efer;
    n1vmcb->_cr0 = v->arch.hvm.guest_cr[0];
    n1vmcb->_cr2 = v->arch.hvm.guest_cr[2];
    n1vmcb->_cr4 = v->arch.hvm.guest_cr[4];

    /* Remember the host interrupt flag */
    svm->ns_hostflags.fields.rflagsif = !!(n1vmcb->rflags & X86_EFLAGS_IF);

    return 0;
}

static int nsvm_vcpu_hostrestore(struct vcpu *v, struct cpu_user_regs *regs)
{
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct vmcb_struct *n1vmcb, *n2vmcb;
    int rc;

    n1vmcb = nv->nv_n1vmcx;
    n2vmcb = nv->nv_n2vmcx;
    ASSERT(n1vmcb != NULL);
    ASSERT(n2vmcb != NULL);

    /*
     * nsvm_vmcb_prepare4vmexit() already saved register values
     * handled by VMSAVE/VMLOAD into n1vmcb directly.
     */

    /* switch vmcb to l1 guest's vmcb */
    v->arch.hvm.svm.vmcb = n1vmcb;
    v->arch.hvm.svm.vmcb_pa = nv->nv_n1vmcx_pa;

    /* EFER */
    v->arch.hvm.guest_efer = n1vmcb->_efer;
    rc = hvm_set_efer(n1vmcb->_efer);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_efer failed, rc: %u\n", rc);

    /* CR4 */
    v->arch.hvm.guest_cr[4] = n1vmcb->_cr4;
    rc = hvm_set_cr4(n1vmcb->_cr4, true);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_cr4 failed, rc: %u\n", rc);

    /* CR0 */
    v->arch.hvm.guest_cr[0] = n1vmcb->_cr0 | X86_CR0_PE;
    n1vmcb->rflags &= ~X86_EFLAGS_VM;
    rc = hvm_set_cr0(n1vmcb->_cr0 | X86_CR0_PE, true);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_cr0 failed, rc: %u\n", rc);

    /* CR2 */
    v->arch.hvm.guest_cr[2] = n1vmcb->_cr2;
    hvm_update_guest_cr(v, 2);

    /* CR3 */
    /* Nested paging mode */
    if ( nestedhvm_paging_mode_hap(v) )
    {
        /* host nested paging + guest nested paging. */
        /* hvm_set_cr3() below sets v->arch.hvm.guest_cr[3] for us. */
    }
    else if ( paging_mode_hap(v->domain) )
    {
        /* host nested paging + guest shadow paging. */
        /* hvm_set_cr3() below sets v->arch.hvm.guest_cr[3] for us. */
    }
    else
    {
        /* host shadow paging + guest shadow paging. */

        /* Reset MMU context  -- XXX (hostrestore) not yet working*/
        if ( !pagetable_is_null(v->arch.guest_table) )
            put_page(pagetable_get_page(v->arch.guest_table));
        v->arch.guest_table = pagetable_null();
        /* hvm_set_cr3() below sets v->arch.hvm.guest_cr[3] for us. */
    }
    rc = hvm_set_cr3(n1vmcb->_cr3, false, true);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_cr3 failed, rc: %u\n", rc);

    regs->rax = n1vmcb->rax;
    regs->rsp = n1vmcb->rsp;
    regs->rip = n1vmcb->rip;
    regs->rflags = n1vmcb->rflags;
    n1vmcb->_dr7 = 0; /* disable all breakpoints */
    n1vmcb->_cpl = 0;

    /*
     * Clear exitintinfo to prevent a fault loop of re-injecting
     * exceptions forever.
     */
    n1vmcb->exit_int_info.raw = 0;

    /* Cleanbits */
    n1vmcb->cleanbits.raw = 0;

    return 0;
}

static int nsvm_vmrun_permissionmap(struct vcpu *v, bool viopm)
{
    struct svm_vcpu *arch_svm = &v->arch.hvm.svm;
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct vmcb_struct *ns_vmcb = nv->nv_vvmcx;
    struct vmcb_struct *host_vmcb = arch_svm->vmcb;
    unsigned long *ns_msrpm_ptr;
    unsigned int i;
    enum hvm_translation_result ret;
    unsigned long *ns_viomap;
    bool ioport_80 = true, ioport_ed = true;

    ns_msrpm_ptr = (unsigned long *)svm->ns_cached_msrpm;

    ret = hvm_copy_from_guest_phys(svm->ns_cached_msrpm,
                                   ns_vmcb->_msrpm_base_pa, MSRPM_SIZE);
    if ( ret != HVMTRANS_okay )
    {
        gdprintk(XENLOG_ERR, "hvm_copy_from_guest_phys msrpm %u\n", ret);
        return 1;
    }

    /* Check l1 guest io permission map and get a shadow one based on
     * if l1 guest intercepts io ports 0x80 and/or 0xED.
     */
    svm->ns_oiomap_pa = svm->ns_iomap_pa;
    svm->ns_iomap_pa = ns_vmcb->_iopm_base_pa;

    ns_viomap = hvm_map_guest_frame_ro(svm->ns_iomap_pa >> PAGE_SHIFT, 0);
    if ( ns_viomap )
    {
        ioport_80 = test_bit(0x80, ns_viomap);
        ioport_ed = test_bit(0xed, ns_viomap);
        hvm_unmap_guest_frame(ns_viomap, 0);
    }

    svm->ns_iomap = nestedhvm_vcpu_iomap_get(ioport_80, ioport_ed);

    nv->nv_ioport80 = ioport_80;
    nv->nv_ioportED = ioport_ed;

    /* v->arch.hvm.svm.msrpm has type unsigned long, thus BYTES_PER_LONG. */
    for ( i = 0; i < MSRPM_SIZE / BYTES_PER_LONG; i++ )
        svm->ns_merged_msrpm[i] = arch_svm->msrpm[i] | ns_msrpm_ptr[i];

    host_vmcb->_iopm_base_pa  = virt_to_maddr(svm->ns_iomap);
    host_vmcb->_msrpm_base_pa = virt_to_maddr(svm->ns_merged_msrpm);

    return 0;
}

static void nestedsvm_vmcb_set_nestedp2m(struct vcpu *v,
    struct vmcb_struct *vvmcb, struct vmcb_struct *n2vmcb)
{
    struct p2m_domain *p2m;

    ASSERT(v != NULL);
    ASSERT(vvmcb != NULL);
    ASSERT(n2vmcb != NULL);

    /* This will allow nsvm_vcpu_hostcr3() to return correct np2m_base */
    vcpu_nestedsvm(v).ns_vmcb_hostcr3 = vvmcb->_h_cr3;

    p2m = p2m_get_nestedp2m(v);
    n2vmcb->_h_cr3 = pagetable_get_paddr(p2m_get_pagetable(p2m));
}

static int nsvm_vmcb_prepare4vmrun(struct vcpu *v, struct cpu_user_regs *regs)
{
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *ns_vmcb, *n1vmcb, *n2vmcb;
    vmcbcleanbits_t clean = {};
    int rc;

    ns_vmcb = nv->nv_vvmcx;
    n1vmcb = nv->nv_n1vmcx;
    n2vmcb = nv->nv_n2vmcx;
    ASSERT(ns_vmcb != NULL);
    ASSERT(n1vmcb != NULL);
    ASSERT(n2vmcb != NULL);

    /* Check if virtual VMCB cleanbits are valid */
    if ( svm->ns_ovvmcb_pa != INVALID_PADDR &&
         svm->ns_ovvmcb_pa == nv->nv_vvmcxaddr )
        clean = ns_vmcb->cleanbits;

    /* Enable l2 guest intercepts */
    if ( !clean.intercepts )
    {
        svm->ns_cr_intercepts = ns_vmcb->_cr_intercepts;
        svm->ns_dr_intercepts = ns_vmcb->_dr_intercepts;
        svm->ns_exception_intercepts = ns_vmcb->_exception_intercepts;
        svm->ns_general1_intercepts = ns_vmcb->_general1_intercepts;
        svm->ns_general2_intercepts = ns_vmcb->_general2_intercepts;
    }

    /* We could track the cleanbits of the n1vmcb from
     * last emulated #VMEXIT to this emulated VMRUN to safe the merges
     * below. Those cleanbits would be tracked in an integer field
     * in struct nestedsvm.
     * But this effort is not worth doing because:
     * - Only the intercepts bit of the n1vmcb can effectively be used here
     * - The CPU runs more instructions for the tracking than can be
     *   safed here.
     * The overhead comes from (ordered from highest to lowest):
     * - svm_ctxt_switch_to (CPU context switching)
     * - emulated CLGI (clears VINTR intercept)
     * - host clears VINTR intercept
     * Test results show that the overhead is high enough that the
     * tracked intercepts bit of the n1vmcb is practically *always* cleared.
     */

    n2vmcb->_cr_intercepts =
        n1vmcb->_cr_intercepts | ns_vmcb->_cr_intercepts;
    n2vmcb->_dr_intercepts =
        n1vmcb->_dr_intercepts | ns_vmcb->_dr_intercepts;
    n2vmcb->_exception_intercepts =
        n1vmcb->_exception_intercepts | ns_vmcb->_exception_intercepts;
    n2vmcb->_general1_intercepts =
        n1vmcb->_general1_intercepts | ns_vmcb->_general1_intercepts;
    n2vmcb->_general2_intercepts =
        n1vmcb->_general2_intercepts | ns_vmcb->_general2_intercepts;

    /* Nested Pause Filter */
    if ( ns_vmcb->_general1_intercepts & GENERAL1_INTERCEPT_PAUSE )
        n2vmcb->_pause_filter_count =
            min(n1vmcb->_pause_filter_count, ns_vmcb->_pause_filter_count);
    else
        n2vmcb->_pause_filter_count = n1vmcb->_pause_filter_count;

    /* TSC offset */
    n2vmcb->_tsc_offset = n1vmcb->_tsc_offset + ns_vmcb->_tsc_offset;

    /* Nested IO permission bitmaps */
    rc = nsvm_vmrun_permissionmap(v, clean.iopm);
    if ( rc )
        return rc;

    /* ASID - Emulation handled in hvm_asid_handle_vmenter() */

    /* TLB control */
    n2vmcb->tlb_control = ns_vmcb->tlb_control;

    /* Virtual Interrupts */
    if ( !clean.tpr )
    {
        n2vmcb->_vintr = ns_vmcb->_vintr;
        n2vmcb->_vintr.fields.intr_masking = 1;
    }

    /* Interrupt state */
    n2vmcb->int_stat = ns_vmcb->int_stat;

    /* Exit codes */
    n2vmcb->exitcode = ns_vmcb->exitcode;
    n2vmcb->exitinfo1 = ns_vmcb->exitinfo1;
    n2vmcb->exitinfo2 = ns_vmcb->exitinfo2;
    n2vmcb->exit_int_info = ns_vmcb->exit_int_info;

    /* Pending Interrupts */
    n2vmcb->event_inj = ns_vmcb->event_inj;

    n2vmcb->virt_ext.bytes =
        n1vmcb->virt_ext.bytes | ns_vmcb->virt_ext.bytes;

    /* NextRIP - only evaluated on #VMEXIT. */

    /*
     * VMCB Save State Area
     */

    /* Segments */
    if ( !clean.seg )
    {
        n2vmcb->es = ns_vmcb->es;
        n2vmcb->cs = ns_vmcb->cs;
        n2vmcb->ss = ns_vmcb->ss;
        n2vmcb->ds = ns_vmcb->ds;
        /* CPL */
        n2vmcb->_cpl = ns_vmcb->_cpl;
    }
    if ( !clean.dt )
    {
        n2vmcb->gdtr = ns_vmcb->gdtr;
        n2vmcb->idtr = ns_vmcb->idtr;
    }

    /* EFER */
    v->arch.hvm.guest_efer = ns_vmcb->_efer;
    rc = hvm_set_efer(ns_vmcb->_efer);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_efer failed, rc: %u\n", rc);

    /* CR4 */
    v->arch.hvm.guest_cr[4] = ns_vmcb->_cr4;
    rc = hvm_set_cr4(ns_vmcb->_cr4, true);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_cr4 failed, rc: %u\n", rc);

    /* CR0 */
    v->arch.hvm.guest_cr[0] = ns_vmcb->_cr0;
    rc = hvm_set_cr0(ns_vmcb->_cr0, true);
    if ( rc == X86EMUL_EXCEPTION )
        hvm_inject_hw_exception(X86_EXC_GP, 0);
    if ( rc != X86EMUL_OKAY )
        gdprintk(XENLOG_ERR, "hvm_set_cr0 failed, rc: %u\n", rc);

    /* CR2 */
    v->arch.hvm.guest_cr[2] = ns_vmcb->_cr2;
    hvm_update_guest_cr(v, 2);

    /* Nested paging mode */
    if ( nestedhvm_paging_mode_hap(v) )
    {
        /* host nested paging + guest nested paging. */
        vmcb_set_np(n2vmcb, true);

        nestedsvm_vmcb_set_nestedp2m(v, ns_vmcb, n2vmcb);

        /* hvm_set_cr3() below sets v->arch.hvm.guest_cr[3] for us. */
        rc = hvm_set_cr3(ns_vmcb->_cr3, false, true);
        if ( rc == X86EMUL_EXCEPTION )
            hvm_inject_hw_exception(X86_EXC_GP, 0);
        if ( rc != X86EMUL_OKAY )
            gdprintk(XENLOG_ERR, "hvm_set_cr3 failed, rc: %u\n", rc);
    }
    else if ( paging_mode_hap(v->domain) )
    {
        /* host nested paging + guest shadow paging. */
        vmcb_set_np(n2vmcb, true);
        /* Keep h_cr3 as it is. */
        n2vmcb->_h_cr3 = n1vmcb->_h_cr3;
        /* When l1 guest does shadow paging
         * we assume it intercepts page faults.
         */
        /* hvm_set_cr3() below sets v->arch.hvm.guest_cr[3] for us. */
        rc = hvm_set_cr3(ns_vmcb->_cr3, false, true);
        if ( rc == X86EMUL_EXCEPTION )
            hvm_inject_hw_exception(X86_EXC_GP, 0);
        if ( rc != X86EMUL_OKAY )
            gdprintk(XENLOG_ERR, "hvm_set_cr3 failed, rc: %u\n", rc);
    }
    else
    {
        /* host shadow paging + guest shadow paging. */
        vmcb_set_np(n2vmcb, false);
        n2vmcb->_h_cr3 = 0x0;

        /* TODO: Once shadow-shadow paging is in place come back to here
         * and set host_vmcb->_cr3 to the shadowed shadow table.
         */
    }

    /* DRn */
    if ( !clean.dr )
    {
        n2vmcb->_dr7 = ns_vmcb->_dr7;
        n2vmcb->_dr6 = ns_vmcb->_dr6;
    }

    /* RFLAGS */
    n2vmcb->rflags = ns_vmcb->rflags;

    /* RIP */
    n2vmcb->rip = ns_vmcb->rip;

    /* RSP */
    n2vmcb->rsp = ns_vmcb->rsp;

    /* RAX */
    n2vmcb->rax = ns_vmcb->rax;

    /* Keep the host values of the fs, gs, ldtr, tr, kerngsbase,
     * star, lstar, cstar, sfmask, sysenter_cs, sysenter_esp,
     * sysenter_eip. These are handled via VMSAVE/VMLOAD emulation.
     */

    /* PAT */
    if ( !clean.np )
        n2vmcb->_g_pat = ns_vmcb->_g_pat;

    if ( !clean.lbr )
    {
        /* Debug Control MSR */
        n2vmcb->_debugctlmsr = ns_vmcb->_debugctlmsr;

        /* LBR MSRs */
        n2vmcb->_lastbranchfromip = ns_vmcb->_lastbranchfromip;
        n2vmcb->_lastbranchtoip = ns_vmcb->_lastbranchtoip;
        n2vmcb->_lastintfromip = ns_vmcb->_lastintfromip;
        n2vmcb->_lastinttoip = ns_vmcb->_lastinttoip;
    }

    /* Cleanbits */
    n2vmcb->cleanbits.raw = 0;

    rc = svm_vmcb_isvalid(__func__, ns_vmcb, v, true);
    if ( rc )
    {
        gdprintk(XENLOG_ERR, "virtual vmcb invalid\n");
        return NSVM_ERROR_VVMCB;
    }

    rc = svm_vmcb_isvalid(__func__, n2vmcb, v, true);
    if ( rc )
    {
        gdprintk(XENLOG_ERR, "n2vmcb invalid\n");
        return NSVM_ERROR_VMENTRY;
    }

    /* Switch guest registers to l2 guest */
    regs->rax = ns_vmcb->rax;
    regs->rip = ns_vmcb->rip;
    regs->rsp = ns_vmcb->rsp;
    regs->rflags = ns_vmcb->rflags;

    return 0;
}

static int
nsvm_vcpu_vmentry(struct vcpu *v, struct cpu_user_regs *regs,
    unsigned int inst_len)
{
    int ret;
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *ns_vmcb;

    ns_vmcb = nv->nv_vvmcx;
    ASSERT(ns_vmcb != NULL);
    ASSERT(nv->nv_n2vmcx != NULL);
    ASSERT(nv->nv_n2vmcx_pa != INVALID_PADDR);

    /* Save values for later use. Needed for Nested-on-Nested and
     * Shadow-on-Shadow paging.
     */
    svm->ns_vmcb_guestcr3 = ns_vmcb->_cr3;
    svm->ns_vmcb_hostcr3 = ns_vmcb->_h_cr3;

    /* Convert explicitely to boolean. Deals with l1 guests
     * that use flush-by-asid w/o checking the cpuid bits */
    nv->nv_flushp2m = !!ns_vmcb->tlb_control;
    if ( svm->ns_asid != vmcb_get_asid(ns_vmcb))
    {
        nv->nv_flushp2m = 1;
        hvm_asid_flush_vcpu_asid(&vcpu_nestedhvm(v).nv_n2asid);
        svm->ns_asid = vmcb_get_asid(ns_vmcb);
    }

    /* nested paging for the guest */
    svm->ns_hap_enabled = vmcb_get_np(ns_vmcb);

    /* Remember the V_INTR_MASK in hostflags */
    svm->ns_hostflags.fields.vintrmask = !!ns_vmcb->_vintr.fields.intr_masking;

    /* Save l1 guest state (= host state) */
    ret = nsvm_vcpu_hostsave(v, inst_len);
    if ( ret )
    {
        gdprintk(XENLOG_ERR, "hostsave failed, ret = %i\n", ret);
        return ret;
    }

    /* switch vmcb to shadow vmcb */
    v->arch.hvm.svm.vmcb = nv->nv_n2vmcx;
    v->arch.hvm.svm.vmcb_pa = nv->nv_n2vmcx_pa;

    ret = nsvm_vmcb_prepare4vmrun(v, regs);
    if ( ret )
    {
        gdprintk(XENLOG_ERR, "prepare4vmrun failed, ret = %i\n", ret);
        return ret;
    }

    svm->ns_gif = 1;
    return 0;
}

int
nsvm_vcpu_vmrun(struct vcpu *v, struct cpu_user_regs *regs)
{
    int ret;
    unsigned int inst_len;
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);

    inst_len = svm_get_insn_len(v, INSTR_VMRUN);
    if ( inst_len == 0 )
    {
        svm->ns_vmexit.exitcode = VMEXIT_SHUTDOWN;
        return -1;
    }

    nv->nv_vmswitch_in_progress = 1;
    ASSERT(nv->nv_vvmcx != NULL);

    /* save host state */
    ret = nsvm_vcpu_vmentry(v, regs, inst_len);

    /* Switch vcpu to guest mode. In the error case
     * this ensures the host mode is restored correctly
     * and l1 guest keeps alive. */
    nestedhvm_vcpu_enter_guestmode(v);

    switch ( ret )
    {
    case 0:
        break;
    case NSVM_ERROR_VVMCB:
        gdprintk(XENLOG_ERR, "inject VMEXIT(INVALID)\n");
        svm->ns_vmexit.exitcode = VMEXIT_INVALID;
        return -1;
    case NSVM_ERROR_VMENTRY:
    default:
        gdprintk(XENLOG_ERR,
            "nsvm_vcpu_vmentry failed, injecting #UD\n");
        hvm_inject_hw_exception(X86_EXC_UD, X86_EVENT_NO_EC);
        /* Must happen after hvm_inject_hw_exception or it doesn't work right. */
        nv->nv_vmswitch_in_progress = 0;
        return 1;
    }

    /* If l1 guest uses shadow paging, update the paging mode. */
    if ( !nestedhvm_paging_mode_hap(v) )
        paging_update_paging_modes(v);

    nv->nv_vmswitch_in_progress = 0;
    return 0;
}

static int
nsvm_vcpu_vmexit_inject(struct vcpu *v, struct cpu_user_regs *regs,
    uint64_t exitcode)
{
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *ns_vmcb;
    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;

    if ( vmcb->_vintr.fields.vgif_enable )
        vmcb->_vintr.fields.vgif = 0;
    else
        svm->ns_gif = 0;

    ns_vmcb = nv->nv_vvmcx;

    if ( nv->nv_vmexit_pending )
    {
        switch ( exitcode )
        {
        case VMEXIT_INTR:
            if ( unlikely(ns_vmcb->event_inj.v) && nv->nv_vmentry_pending &&
                 hvm_event_needs_reinjection(ns_vmcb->event_inj.type,
                                             ns_vmcb->event_inj.vector) )
                ns_vmcb->exit_int_info = ns_vmcb->event_inj;
            break;
        case VMEXIT_EXCEPTION_PF:
            ns_vmcb->_cr2 = ns_vmcb->ei.exc.cr2;
            fallthrough;
        case VMEXIT_NPF:
            ns_vmcb->exitinfo2 = svm->ns_vmexit.exitinfo2;
            fallthrough;
        case VMEXIT_EXCEPTION_NP:
        case VMEXIT_EXCEPTION_SS:
        case VMEXIT_EXCEPTION_GP:
        case VMEXIT_EXCEPTION_15:
        case VMEXIT_EXCEPTION_MF:
        case VMEXIT_EXCEPTION_AC:
            ns_vmcb->exitinfo1 = svm->ns_vmexit.exitinfo1;
            break;
        default:
            break;
        }
    }

    ns_vmcb->exitcode = exitcode;
    ns_vmcb->event_inj.raw = 0;
    return 0;
}

int cf_check nsvm_vcpu_vmexit_event(
    struct vcpu *v, const struct x86_event *event)
{
    ASSERT(vcpu_nestedhvm(v).nv_vvmcx != NULL);

    nestedsvm_vmexit_defer(v, VMEXIT_EXCEPTION_DE + event->vector,
                           event->error_code, event->cr2);
    return NESTEDHVM_VMEXIT_DONE;
}

uint64_t cf_check nsvm_vcpu_hostcr3(struct vcpu *v)
{
    return vcpu_nestedsvm(v).ns_vmcb_hostcr3;
}

static int
nsvm_vmcb_guest_intercepts_msr(unsigned long *msr_bitmap,
    uint32_t msr, bool write)
{
    bool enabled;
    unsigned long *msr_bit;

    msr_bit = svm_msrbit(msr_bitmap, msr);

    if ( msr_bit == NULL )
        /* MSR not in the permission map: Let the guest handle it. */
        return NESTEDHVM_VMEXIT_INJECT;

    msr &= 0x1fff;

    if ( write )
        /* write access */
        enabled = test_bit(msr * 2 + 1, msr_bit);
    else
        /* read access */
        enabled = test_bit(msr * 2, msr_bit);

    if ( !enabled )
        return NESTEDHVM_VMEXIT_HOST;

    return NESTEDHVM_VMEXIT_INJECT;
}

static int
nsvm_vmcb_guest_intercepts_ioio(paddr_t iopm_pa, uint64_t exitinfo1)
{
    unsigned long gfn = iopm_pa >> PAGE_SHIFT;
    unsigned long *io_bitmap;
    ioio_info_t ioinfo;
    uint16_t port;
    unsigned int size;
    bool enabled;

    ioinfo.bytes = exitinfo1;
    port = ioinfo.fields.port;
    size = ioinfo.fields.sz32 ? 4 : ioinfo.fields.sz16 ? 2 : 1;

    switch ( port )
    {
    case 0 ... 8 * PAGE_SIZE - 1: /* first 4KB page */
        break;
    case 8 * PAGE_SIZE ... 2 * 8 * PAGE_SIZE - 1: /* second 4KB page */
        port -= 8 * PAGE_SIZE;
        ++gfn;
        break;
    default:
        BUG();
        break;
    }

    for ( io_bitmap = hvm_map_guest_frame_ro(gfn, 0); ; )
    {
        enabled = io_bitmap && test_bit(port, io_bitmap);
        if ( !enabled || !--size )
            break;
        if ( unlikely(++port == 8 * PAGE_SIZE) )
        {
            hvm_unmap_guest_frame(io_bitmap, 0);
            io_bitmap = hvm_map_guest_frame_ro(++gfn, 0);
            port -= 8 * PAGE_SIZE;
        }
    }
    hvm_unmap_guest_frame(io_bitmap, 0);

    if ( !enabled )
        return NESTEDHVM_VMEXIT_HOST;

    return NESTEDHVM_VMEXIT_INJECT;
}

static bool
nsvm_vmcb_guest_intercepts_exitcode(struct vcpu *v,
    struct cpu_user_regs *regs, uint64_t exitcode)
{
    uint64_t exit_bits;
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *ns_vmcb = nv->nv_vvmcx;
    enum nestedhvm_vmexits vmexits;

    switch ( exitcode )
    {
    case VMEXIT_CR0_READ ... VMEXIT_CR15_READ:
    case VMEXIT_CR0_WRITE ... VMEXIT_CR15_WRITE:
        exit_bits = 1ULL << (exitcode - VMEXIT_CR0_READ);
        if ( svm->ns_cr_intercepts & exit_bits )
            break;
        return 0;

    case VMEXIT_DR0_READ ... VMEXIT_DR7_READ:
    case VMEXIT_DR0_WRITE ... VMEXIT_DR7_WRITE:
        exit_bits = 1ULL << (exitcode - VMEXIT_DR0_READ);
        if ( svm->ns_dr_intercepts & exit_bits )
            break;
        return 0;

    case VMEXIT_EXCEPTION_DE ... VMEXIT_EXCEPTION_XF:
        exit_bits = 1ULL << (exitcode - VMEXIT_EXCEPTION_DE);
        if ( svm->ns_exception_intercepts & exit_bits )
            break;
        return 0;

    case VMEXIT_INTR ... VMEXIT_SHUTDOWN:
        exit_bits = 1ULL << (exitcode - VMEXIT_INTR);
        if ( svm->ns_general1_intercepts & exit_bits )
            break;
        return 0;

    case VMEXIT_VMRUN ... VMEXIT_XSETBV:
        exit_bits = 1ULL << (exitcode - VMEXIT_VMRUN);
        if ( svm->ns_general2_intercepts & exit_bits )
            break;
        return 0;

    case VMEXIT_NPF:
        if ( nestedhvm_paging_mode_hap(v) )
            break;
        return 0;
    case VMEXIT_INVALID:
        /* Always intercepted */
        break;

    default:
        gdprintk(XENLOG_ERR, "Illegal exitcode %#"PRIx64"\n", exitcode);
        BUG();
        break;
    }

    /* Special cases: Do more detailed checks */
    switch ( exitcode )
    {
    case VMEXIT_MSR:
        ASSERT(regs != NULL);
        if ( !nestedsvm_vmcb_map(v, nv->nv_vvmcxaddr) )
            break;
        ns_vmcb = nv->nv_vvmcx;
        vmexits = nsvm_vmcb_guest_intercepts_msr(svm->ns_cached_msrpm,
            regs->ecx, ns_vmcb->exitinfo1 != 0);
        if ( vmexits == NESTEDHVM_VMEXIT_HOST )
            return 0;
        break;
    case VMEXIT_IOIO:
        if ( !nestedsvm_vmcb_map(v, nv->nv_vvmcxaddr) )
            break;
        ns_vmcb = nv->nv_vvmcx;
        vmexits = nsvm_vmcb_guest_intercepts_ioio(ns_vmcb->_iopm_base_pa,
            ns_vmcb->exitinfo1);
        if ( vmexits == NESTEDHVM_VMEXIT_HOST )
            return 0;
        break;
    }

    return 1;
}

bool cf_check nsvm_vmcb_guest_intercepts_event(
    struct vcpu *v, unsigned int vector, int errcode)
{
    return nsvm_vmcb_guest_intercepts_exitcode(v,
        guest_cpu_user_regs(), VMEXIT_EXCEPTION_DE + vector);
}

static int
nsvm_vmcb_prepare4vmexit(struct vcpu *v, struct cpu_user_regs *regs)
{
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *ns_vmcb = nv->nv_vvmcx;
    struct vmcb_struct *n2vmcb = nv->nv_n2vmcx;

    svm_vmsave_pa(nv->nv_n1vmcx_pa);

    /* Cache guest physical address of virtual vmcb
     * for VMCB Cleanbit emulation.
     */
    svm->ns_ovvmcb_pa = nv->nv_vvmcxaddr;

    /* Intercepts - keep them as they are */

    /* Pausefilter - keep it as is */

    /* Nested IO permission bitmap */
    /* Just keep the iopm_base_pa and msrpm_base_pa values.
     * The guest must not see the virtualized values.
     */

    /* TSC offset */
    /* Keep it. It's maintainted by the l1 guest. */

    /* ASID */
    /* vmcb_set_asid(ns_vmcb, vmcb_get_asid(n2vmcb)); */

    /* TLB control */
    ns_vmcb->tlb_control = 0;

    /* Virtual Interrupts */
    ns_vmcb->_vintr = n2vmcb->_vintr;
    if ( !svm->ns_hostflags.fields.vintrmask )
        ns_vmcb->_vintr.fields.intr_masking = 0;

    /* Interrupt state */
    ns_vmcb->int_stat = n2vmcb->int_stat;

    /* Exit codes */
    ns_vmcb->exitcode = n2vmcb->exitcode;
    ns_vmcb->exitinfo1 = n2vmcb->exitinfo1;
    ns_vmcb->exitinfo2 = n2vmcb->exitinfo2;
    ns_vmcb->exit_int_info = n2vmcb->exit_int_info;

    /* Interrupts */
    /* If we emulate a VMRUN/#VMEXIT in the same host #VMEXIT cycle we have
     * to make sure that we do not lose injected events. So check eventinj
     * here and copy it to exitintinfo if it is valid.
     * exitintinfo and eventinj can't be both valid because the case below
     * only happens on a VMRUN instruction intercept which has no valid
     * exitintinfo set.
     */
    if ( unlikely(n2vmcb->event_inj.v) &&
         hvm_event_needs_reinjection(n2vmcb->event_inj.type,
                                     n2vmcb->event_inj.vector) )
        ns_vmcb->exit_int_info = n2vmcb->event_inj;

    ns_vmcb->event_inj.raw = 0;

    /* Nested paging mode */
    if ( nestedhvm_paging_mode_hap(v) )
    {
        /* host nested paging + guest nested paging. */
        vmcb_set_np(ns_vmcb, vmcb_get_np(n2vmcb));
        ns_vmcb->_cr3 = n2vmcb->_cr3;
        /* The vmcb->h_cr3 is the shadowed h_cr3. The original
         * unshadowed guest h_cr3 is kept in ns_vmcb->h_cr3,
         * hence we keep the ns_vmcb->h_cr3 value. */
    }
    else if ( paging_mode_hap(v->domain) )
    {
        /* host nested paging + guest shadow paging. */
        vmcb_set_np(ns_vmcb, false);
        /* Throw h_cr3 away. Guest is not allowed to set it or
         * it can break out, otherwise (security hole!) */
        ns_vmcb->_h_cr3 = 0x0;
        /* Stop intercepting #PF (already done above
         * by restoring cached intercepts). */
        ns_vmcb->_cr3 = n2vmcb->_cr3;
    }
    else
    {
        /* host shadow paging + guest shadow paging. */
        vmcb_set_np(ns_vmcb, false);
        ns_vmcb->_h_cr3 = 0x0;
        /* The vmcb->_cr3 is the shadowed cr3. The original
         * unshadowed guest cr3 is kept in ns_vmcb->_cr3,
         * hence we keep the ns_vmcb->_cr3 value. */
    }

    /* LBR virtualization - keep lbr control as is */

    /* NextRIP */
    ns_vmcb->nextrip = n2vmcb->nextrip;

    /* Decode Assist */
    ns_vmcb->guest_ins_len = n2vmcb->guest_ins_len;
    memcpy(ns_vmcb->guest_ins, n2vmcb->guest_ins, sizeof(ns_vmcb->guest_ins));

    /*
     * VMCB Save State Area
     */

    /* Segments */
    ns_vmcb->es = n2vmcb->es;
    ns_vmcb->cs = n2vmcb->cs;
    ns_vmcb->ss = n2vmcb->ss;
    ns_vmcb->ds = n2vmcb->ds;
    ns_vmcb->gdtr = n2vmcb->gdtr;
    ns_vmcb->idtr = n2vmcb->idtr;

    /* CPL */
    ns_vmcb->_cpl = n2vmcb->_cpl;

    /* EFER */
    ns_vmcb->_efer = n2vmcb->_efer;

    /* CRn */
    ns_vmcb->_cr4 = n2vmcb->_cr4;
    ns_vmcb->_cr0 = n2vmcb->_cr0;

    /* DRn */
    ns_vmcb->_dr7 = n2vmcb->_dr7;
    ns_vmcb->_dr6 = n2vmcb->_dr6;

    /* Restore registers from regs as those values
     * can be newer than in n2vmcb (e.g. due to an
     * instruction emulation right before).
     */

    /* RFLAGS */
    ns_vmcb->rflags = n2vmcb->rflags = regs->rflags;

    /* RIP */
    ns_vmcb->rip = n2vmcb->rip = regs->rip;

    /* RSP */
    ns_vmcb->rsp = n2vmcb->rsp = regs->rsp;

    /* RAX */
    ns_vmcb->rax = n2vmcb->rax = regs->rax;

    /* Keep the l2 guest values of the fs, gs, ldtr, tr, kerngsbase,
     * star, lstar, cstar, sfmask, sysenter_cs, sysenter_esp,
     * sysenter_eip. These are handled via VMSAVE/VMLOAD emulation.
     */

    /* CR2 */
    ns_vmcb->_cr2 = n2vmcb->_cr2;

    /* PAT */
    ns_vmcb->_g_pat = n2vmcb->_g_pat;

    /* Debug Control MSR */
    ns_vmcb->_debugctlmsr = n2vmcb->_debugctlmsr;

    /* LBR MSRs */
    ns_vmcb->_lastbranchfromip = n2vmcb->_lastbranchfromip;
    ns_vmcb->_lastbranchtoip = n2vmcb->_lastbranchtoip;
    ns_vmcb->_lastintfromip = n2vmcb->_lastintfromip;
    ns_vmcb->_lastinttoip = n2vmcb->_lastinttoip;

    return 0;
}

bool cf_check nsvm_vmcb_hap_enabled(struct vcpu *v)
{
    return vcpu_nestedsvm(v).ns_hap_enabled;
}

/* This function uses L2_gpa to walk the P2M page table in L1. If the
 * walk is successful, the translated value is returned in
 * L1_gpa. The result value tells what to do next.
 */
int cf_check nsvm_hap_walk_L1_p2m(
    struct vcpu *v, paddr_t L2_gpa, paddr_t *L1_gpa, unsigned int *page_order,
    uint8_t *p2m_acc, struct npfec npfec)
{
    uint32_t pfec;
    unsigned long nested_cr3, gfn;

    nested_cr3 = nhvm_vcpu_p2m_base(v);

    pfec = PFEC_user_mode | PFEC_page_present;
    if ( npfec.write_access )
        pfec |= PFEC_write_access;
    if ( npfec.insn_fetch )
        pfec |= PFEC_insn_fetch;

    /* Walk the guest-supplied NPT table, just as if it were a pagetable */
    gfn = paging_ga_to_gfn_cr3(v, nested_cr3, L2_gpa, &pfec, page_order);

    if ( gfn == gfn_x(INVALID_GFN) )
        return NESTEDHVM_PAGEFAULT_INJECT;

    *L1_gpa = (gfn << PAGE_SHIFT) + (L2_gpa & ~PAGE_MASK);
    return NESTEDHVM_PAGEFAULT_DONE;
}

enum hvm_intblk cf_check nsvm_intr_blocked(struct vcpu *v)
{
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);

    ASSERT(nestedhvm_enabled(v->domain));

    if ( !nestedsvm_gif_isset(v) )
        return hvm_intblk_svm_gif;

    if ( nestedhvm_vcpu_in_guestmode(v) )
    {
        struct vmcb_struct *n2vmcb = nv->nv_n2vmcx;

        if ( svm->ns_hostflags.fields.vintrmask &&
             !svm->ns_hostflags.fields.rflagsif )
            return hvm_intblk_rflags_ie;

        /* when l1 guest passes its devices through to the l2 guest
         * and l2 guest does an MMIO access then we may want to
         * inject an VMEXIT(#INTR) exitcode into the l1 guest.
         * Delay the injection because this would result in delivering
         * an interrupt *within* the execution of an instruction.
         */
        if ( v->io.req.state != STATE_IOREQ_NONE )
            return hvm_intblk_shadow;

        if ( !nv->nv_vmexit_pending && n2vmcb->exit_int_info.v )
        {
            /* Give the l2 guest a chance to finish the delivery of
             * the last injected interrupt or exception before we
             * emulate a VMEXIT (e.g. VMEXIT(INTR) ).
             */
            return hvm_intblk_shadow;
        }
    }

    if ( nv->nv_vmexit_pending )
        /* hvm_inject_hw_exception() must have run before.
         * exceptions have higher priority than interrupts.
         */
        return hvm_intblk_rflags_ie;

    return hvm_intblk_none;
}

/* VMEXIT emulation */
void
nestedsvm_vmexit_defer(struct vcpu *v,
    uint64_t exitcode, uint64_t exitinfo1, uint64_t exitinfo2)
{
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;

    if ( vmcb->_vintr.fields.vgif_enable )
        vmcb->_vintr.fields.vgif = 0;
    else
        svm->ns_gif = 0;

    svm->ns_vmexit.exitcode = exitcode;
    svm->ns_vmexit.exitinfo1 = exitinfo1;
    svm->ns_vmexit.exitinfo2 = exitinfo2;
    vcpu_nestedhvm(v).nv_vmexit_pending = 1;
}

enum nestedhvm_vmexits
nestedsvm_check_intercepts(struct vcpu *v, struct cpu_user_regs *regs,
    uint64_t exitcode)
{
    bool is_intercepted;

    ASSERT(vcpu_nestedhvm(v).nv_vmexit_pending == 0);
    is_intercepted = nsvm_vmcb_guest_intercepts_exitcode(v, regs, exitcode);

    /* 
     * Handle specific interactions between things the guest and host
     * may both want to intercept
     */
    switch ( exitcode )
    {
    case VMEXIT_INVALID:
        if ( is_intercepted )
            return NESTEDHVM_VMEXIT_INJECT;
        return NESTEDHVM_VMEXIT_HOST;

    case VMEXIT_INTR:
    case VMEXIT_NMI:
        return NESTEDHVM_VMEXIT_HOST;

    case VMEXIT_NPF:
        if ( nestedhvm_paging_mode_hap(v) )
        {
            if ( !is_intercepted )
                return NESTEDHVM_VMEXIT_FATALERROR;
            /* host nested paging + guest nested paging */
            return NESTEDHVM_VMEXIT_HOST;
        }
        if ( paging_mode_hap(v->domain) )
        {
            if ( is_intercepted )
                return NESTEDHVM_VMEXIT_FATALERROR;
            /* host nested paging + guest shadow paging */
            return NESTEDHVM_VMEXIT_HOST;
        }
        /* host shadow paging + guest shadow paging */
        /* Can this happen? */
        BUG();

    case VMEXIT_EXCEPTION_PF:
        if ( nestedhvm_paging_mode_hap(v) )
        {
            /* host nested paging + guest nested paging */
            if ( !is_intercepted )
                /* l1 guest intercepts #PF unnecessarily */
                return NESTEDHVM_VMEXIT_HOST;
            /* l2 guest intercepts #PF unnecessarily */
            return NESTEDHVM_VMEXIT_INJECT;
        }
        if ( paging_mode_shadow(v->domain) )
            /* host shadow paging + guest shadow paging */
            return NESTEDHVM_VMEXIT_HOST;

        /* host nested paging + guest shadow paging */
        return NESTEDHVM_VMEXIT_INJECT;
    case VMEXIT_VMMCALL:
        /* Always let the guest handle VMMCALL/VMCALL */
        return NESTEDHVM_VMEXIT_INJECT;
    default:
        break;
    }

    if ( is_intercepted )
        return NESTEDHVM_VMEXIT_INJECT;
    return NESTEDHVM_VMEXIT_HOST;
}

enum nestedhvm_vmexits
nestedsvm_vmexit_n2n1(struct vcpu *v, struct cpu_user_regs *regs)
{
    int rc;
    enum nestedhvm_vmexits ret = NESTEDHVM_VMEXIT_DONE;

    ASSERT(vcpu_nestedhvm(v).nv_vmswitch_in_progress);
    ASSERT(nestedhvm_vcpu_in_guestmode(v));

    rc = nsvm_vmcb_prepare4vmexit(v, regs);
    if ( rc )
        ret = NESTEDHVM_VMEXIT_ERROR;

    rc = nsvm_vcpu_hostrestore(v, regs);
    if ( rc )
        ret = NESTEDHVM_VMEXIT_FATALERROR;

    nestedhvm_vcpu_exit_guestmode(v);
    return ret;
}

/* The exitcode is in native SVM/VMX format. The forced exitcode
 * is in generic format.
 */
static enum nestedhvm_vmexits
nestedsvm_vcpu_vmexit(struct vcpu *v, struct cpu_user_regs *regs,
    uint64_t exitcode)
{
    int rc;
    struct nestedvcpu *nv = &vcpu_nestedhvm(v);

    nv->nv_vmswitch_in_progress = 1;

    ASSERT(nv->nv_vvmcx != NULL);

    /* On special intercepts the host has to handle
     * the vcpu is still in guest mode here.
     */
    if ( nestedhvm_vcpu_in_guestmode(v) )
    {
        enum nestedhvm_vmexits ret;

        ret = nestedsvm_vmexit_n2n1(v, regs);
        switch ( ret )
        {
        case NESTEDHVM_VMEXIT_FATALERROR:
            gdprintk(XENLOG_ERR, "VMEXIT: fatal error\n");
            return ret;
        case NESTEDHVM_VMEXIT_HOST:
            BUG();

        case NESTEDHVM_VMEXIT_ERROR:
            exitcode = VMEXIT_INVALID;
            break;
        default:
            ASSERT(!nestedhvm_vcpu_in_guestmode(v));
            break;
        }

        /* host state has been restored */
    }

    ASSERT(!nestedhvm_vcpu_in_guestmode(v));

    /* Prepare for running the l1 guest. Make the actual
     * modifications to the virtual VMCB/VMCS.
     */
    rc = nsvm_vcpu_vmexit_inject(v, regs, exitcode);

    /* If l1 guest uses shadow paging, update the paging mode. */
    if ( !nestedhvm_paging_mode_hap(v) )
        paging_update_paging_modes(v);

    nv->nv_vmswitch_in_progress = 0;

    if ( rc )
        return NESTEDHVM_VMEXIT_FATALERROR;

    return NESTEDHVM_VMEXIT_DONE;
}

/* VCPU switch */
void asmlinkage nsvm_vcpu_switch(void)
{
    struct cpu_user_regs *regs = guest_cpu_user_regs();
    struct vcpu *v = current;
    struct nestedvcpu *nv;
    struct nestedsvm *svm;

    if ( !nestedhvm_enabled(v->domain) )
        return;

    nv = &vcpu_nestedhvm(v);
    svm = &vcpu_nestedsvm(v);
    ASSERT(v->arch.hvm.svm.vmcb != NULL);
    ASSERT(nv->nv_n1vmcx != NULL);
    ASSERT(nv->nv_n2vmcx != NULL);
    ASSERT(nv->nv_n1vmcx_pa != INVALID_PADDR);
    ASSERT(nv->nv_n2vmcx_pa != INVALID_PADDR);

    if ( nv->nv_vmexit_pending )
    {
    vmexit:
        nestedsvm_vcpu_vmexit(v, regs, svm->ns_vmexit.exitcode);
        nv->nv_vmexit_pending = 0;
        nv->nv_vmentry_pending = 0;
        return;
    }

    if ( nv->nv_vmentry_pending )
    {
        int ret;
        ASSERT(!nv->nv_vmexit_pending);
        ret = nsvm_vcpu_vmrun(v, regs);
        if ( ret )
            goto vmexit;

        ASSERT(nestedhvm_vcpu_in_guestmode(v));
        nv->nv_vmentry_pending = 0;
    }

    if ( nestedhvm_vcpu_in_guestmode(v) && nestedhvm_paging_mode_hap(v) )
    {
        /* In case left the l2 guest due to a physical interrupt (e.g. IPI)
         * that is not for the l1 guest then we continue running the l2 guest
         * but check if the nestedp2m is still valid.
         */
        if ( nv->nv_p2m == NULL )
            nestedsvm_vmcb_set_nestedp2m(v, nv->nv_vvmcx, nv->nv_n2vmcx);
    }
}

/* Interrupts, Virtual GIF */
int
nestedsvm_vcpu_interrupt(struct vcpu *v, const struct hvm_intack intack)
{
    int ret;
    enum hvm_intblk intr;
    uint64_t exitcode = VMEXIT_INTR;
    uint64_t exitinfo2 = 0;
    ASSERT(nestedhvm_vcpu_in_guestmode(v));

    intr = nhvm_interrupt_blocked(v);
    if ( intr != hvm_intblk_none )
        return NSVM_INTR_MASKED;

    switch ( intack.source )
    {
    case hvm_intsrc_pic:
    case hvm_intsrc_lapic:
    case hvm_intsrc_vector:
        exitcode = VMEXIT_INTR;
        exitinfo2 = intack.vector;
        break;
    case hvm_intsrc_nmi:
        exitcode = VMEXIT_NMI;
        exitinfo2 = intack.vector;
        break;
    case hvm_intsrc_mce:
        exitcode = VMEXIT_EXCEPTION_MC;
        exitinfo2 = intack.vector;
        break;
    case hvm_intsrc_none:
        return NSVM_INTR_NOTHANDLED;
    default:
        BUG();
    }

    ret = nsvm_vmcb_guest_intercepts_exitcode(v,
                                     guest_cpu_user_regs(), exitcode);
    if ( ret )
    {
        nestedsvm_vmexit_defer(v, exitcode, intack.source, exitinfo2);
        return NSVM_INTR_FORCEVMEXIT;
    }

    return NSVM_INTR_NOTINTERCEPTED;
}

bool
nestedsvm_gif_isset(struct vcpu *v)
{
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;

    /* get the vmcb gif value if using vgif */
    if ( vmcb->_vintr.fields.vgif_enable )
        return vmcb->_vintr.fields.vgif;
    else
        return svm->ns_gif;
}

void svm_vmexit_do_stgi(struct cpu_user_regs *regs, struct vcpu *v)
{
    unsigned int inst_len;

    /*
     * STGI doesn't require SVME to be set to be used.  See AMD APM vol
     * 2 section 15.4 for details.
     */
    if ( !nestedhvm_enabled(v->domain) )
    {
        hvm_inject_hw_exception(X86_EXC_UD, X86_EVENT_NO_EC);
        return;
    }

    if ( (inst_len = svm_get_insn_len(v, INSTR_STGI)) == 0 )
        return;

    vcpu_nestedsvm(v).ns_gif = 1;

    __update_guest_eip(regs, inst_len);
}

void svm_vmexit_do_clgi(struct cpu_user_regs *regs, struct vcpu *v)
{
    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
    unsigned int inst_len;
    uint32_t general1_intercepts = vmcb_get_general1_intercepts(vmcb);
    vintr_t intr;

    if ( !nsvm_efer_svm_enabled(v) )
    {
        hvm_inject_hw_exception(X86_EXC_UD, X86_EVENT_NO_EC);
        return;
    }

    if ( (inst_len = svm_get_insn_len(v, INSTR_CLGI)) == 0 )
        return;

    vcpu_nestedsvm(v).ns_gif = 0;

    /* After a CLGI no interrupts should come */
    intr = vmcb_get_vintr(vmcb);
    intr.fields.irq = 0;
    general1_intercepts &= ~GENERAL1_INTERCEPT_VINTR;
    vmcb_set_vintr(vmcb, intr);
    vmcb_set_general1_intercepts(vmcb, general1_intercepts);

    __update_guest_eip(regs, inst_len);
}

/*
 * This runs on EFER change to see if nested features need to either be
 * turned off or on.
 */
void svm_nested_features_on_efer_update(struct vcpu *v)
{
    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
    struct nestedsvm *svm = &vcpu_nestedsvm(v);
    u32 general2_intercepts;
    vintr_t vintr;

    /*
     * Need state for transfering the nested gif status so only write on
     * the hvm_vcpu EFER.SVME changing.
     */
    if ( nsvm_efer_svm_enabled(v) )
    {
        if ( !vmcb->virt_ext.fields.vloadsave_enable &&
             paging_mode_hap(v->domain) &&
             cpu_has_svm_vloadsave )
        {
            vmcb->virt_ext.fields.vloadsave_enable = 1;
            general2_intercepts  = vmcb_get_general2_intercepts(vmcb);
            general2_intercepts &= ~(GENERAL2_INTERCEPT_VMLOAD |
                                     GENERAL2_INTERCEPT_VMSAVE);
            vmcb_set_general2_intercepts(vmcb, general2_intercepts);
        }

        if ( !vmcb->_vintr.fields.vgif_enable &&
             cpu_has_svm_vgif )
        {
            vintr = vmcb_get_vintr(vmcb);
            vintr.fields.vgif = svm->ns_gif;
            vintr.fields.vgif_enable = 1;
            vmcb_set_vintr(vmcb, vintr);
            general2_intercepts  = vmcb_get_general2_intercepts(vmcb);
            general2_intercepts &= ~(GENERAL2_INTERCEPT_STGI |
                                     GENERAL2_INTERCEPT_CLGI);
            vmcb_set_general2_intercepts(vmcb, general2_intercepts);
        }
    }
    else
    {
        if ( vmcb->virt_ext.fields.vloadsave_enable )
        {
            vmcb->virt_ext.fields.vloadsave_enable = 0;
            general2_intercepts  = vmcb_get_general2_intercepts(vmcb);
            general2_intercepts |= (GENERAL2_INTERCEPT_VMLOAD |
                                    GENERAL2_INTERCEPT_VMSAVE);
            vmcb_set_general2_intercepts(vmcb, general2_intercepts);
        }

        if ( vmcb->_vintr.fields.vgif_enable )
        {
            vintr = vmcb_get_vintr(vmcb);
            svm->ns_gif = vintr.fields.vgif;
            vintr.fields.vgif_enable = 0;
            vmcb_set_vintr(vmcb, vintr);
            general2_intercepts  = vmcb_get_general2_intercepts(vmcb);
            general2_intercepts |= (GENERAL2_INTERCEPT_STGI |
                                    GENERAL2_INTERCEPT_CLGI);
            vmcb_set_general2_intercepts(vmcb, general2_intercepts);
        }
    }
}

void __init start_nested_svm(struct hvm_function_table *hvm_function_table)
{
    /* 
     * Required host functionality to support nested virt.  See
     * docs/designs/nested-svm-cpu-features.md for rationale.
     */
    hvm_function_table->caps.nested_virt =
        hvm_function_table->caps.hap && 
        cpu_has_svm_lbrv &&
        cpu_has_svm_nrips &&
        cpu_has_svm_flushbyasid &&
        cpu_has_svm_decode;
}
