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    SubjectRe: [PATCH v6 08/14] KVM/nVMX: Use kvm_vcpu_map when mapping the posted interrupt descriptor table
    On Thu, Jan 31, 2019 at 12:28 PM KarimAllah Ahmed <karahmed@amazon.de> wrote:
    >
    > Use kvm_vcpu_map when mapping the posted interrupt descriptor table since
    > using kvm_vcpu_gpa_to_page() and kmap() will only work for guest memory
    > that has a "struct page".
    >
    > One additional semantic change is that the virtual host mapping lifecycle
    > has changed a bit. It now has the same lifetime of the pinning of the
    > interrupt descriptor table page on the host side.
    >
    > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
    > Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    > ---
    > v4 -> v5:
    > - unmap with dirty flag
    >
    > v1 -> v2:
    > - Do not change the lifecycle of the mapping (pbonzini)
    > ---
    > arch/x86/kvm/vmx/nested.c | 43 ++++++++++++-------------------------------
    > arch/x86/kvm/vmx/vmx.h | 2 +-
    > 2 files changed, 13 insertions(+), 32 deletions(-)
    >
    > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
    > index 31b352c..53b1063 100644
    > --- a/arch/x86/kvm/vmx/nested.c
    > +++ b/arch/x86/kvm/vmx/nested.c
    > @@ -230,12 +230,8 @@ static void free_nested(struct kvm_vcpu *vcpu)
    > vmx->nested.apic_access_page = NULL;
    > }
    > kvm_vcpu_unmap(vcpu, &vmx->nested.virtual_apic_map, true);
    > - if (vmx->nested.pi_desc_page) {
    > - kunmap(vmx->nested.pi_desc_page);
    > - kvm_release_page_dirty(vmx->nested.pi_desc_page);
    > - vmx->nested.pi_desc_page = NULL;
    > - vmx->nested.pi_desc = NULL;
    > - }
    > + kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map, true);
    > + vmx->nested.pi_desc = NULL;
    >
    > kvm_mmu_free_roots(vcpu, &vcpu->arch.guest_mmu, KVM_MMU_ROOTS_ALL);
    >
    > @@ -2868,26 +2864,15 @@ static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu)
    > }
    >
    > if (nested_cpu_has_posted_intr(vmcs12)) {
    > - if (vmx->nested.pi_desc_page) { /* shouldn't happen */
    > - kunmap(vmx->nested.pi_desc_page);
    > - kvm_release_page_dirty(vmx->nested.pi_desc_page);
    > - vmx->nested.pi_desc_page = NULL;
    > - vmx->nested.pi_desc = NULL;
    > - vmcs_write64(POSTED_INTR_DESC_ADDR, -1ull);
    > + map = &vmx->nested.pi_desc_map;
    > +
    > + if (!kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->posted_intr_desc_addr), map)) {
    > + vmx->nested.pi_desc =
    > + (struct pi_desc *)(((void *)map->hva) +
    > + offset_in_page(vmcs12->posted_intr_desc_addr));
    > + vmcs_write64(POSTED_INTR_DESC_ADDR,
    > + pfn_to_hpa(map->pfn) + offset_in_page(vmcs12->posted_intr_desc_addr));
    > }

    Previously, if there was no backing page for the
    vmcs12->posted_intr_desc_addr, we wrote an illegal value (-1ull) into
    the vmcs02 POSTED_INTR_DESC_ADDR field to force VM-entry failure. Now,
    AFAICT, we leave that field unmodified. For a newly constructed
    vmcs02, doesn't that mean we're going to treat physical address 0 as
    the address of the vmcs02 posted interrupt descriptor?

    > - page = kvm_vcpu_gpa_to_page(vcpu, vmcs12->posted_intr_desc_addr);
    > - if (is_error_page(page))
    > - return;
    > - vmx->nested.pi_desc_page = page;
    > - vmx->nested.pi_desc = kmap(vmx->nested.pi_desc_page);
    > - vmx->nested.pi_desc =
    > - (struct pi_desc *)((void *)vmx->nested.pi_desc +
    > - (unsigned long)(vmcs12->posted_intr_desc_addr &
    > - (PAGE_SIZE - 1)));
    > - vmcs_write64(POSTED_INTR_DESC_ADDR,
    > - page_to_phys(vmx->nested.pi_desc_page) +
    > - (unsigned long)(vmcs12->posted_intr_desc_addr &
    > - (PAGE_SIZE - 1)));
    > }
    > if (nested_vmx_prepare_msr_bitmap(vcpu, vmcs12))
    > vmcs_set_bits(CPU_BASED_VM_EXEC_CONTROL,
    > @@ -3911,12 +3896,8 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 exit_reason,
    > vmx->nested.apic_access_page = NULL;
    > }
    > kvm_vcpu_unmap(vcpu, &vmx->nested.virtual_apic_map, true);
    > - if (vmx->nested.pi_desc_page) {
    > - kunmap(vmx->nested.pi_desc_page);
    > - kvm_release_page_dirty(vmx->nested.pi_desc_page);
    > - vmx->nested.pi_desc_page = NULL;
    > - vmx->nested.pi_desc = NULL;
    > - }
    > + kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map, true);
    > + vmx->nested.pi_desc = NULL;
    >
    > /*
    > * We are now running in L2, mmu_notifier will force to reload the
    > diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h
    > index f618f52..bd04725 100644
    > --- a/arch/x86/kvm/vmx/vmx.h
    > +++ b/arch/x86/kvm/vmx/vmx.h
    > @@ -143,7 +143,7 @@ struct nested_vmx {
    > */
    > struct page *apic_access_page;
    > struct kvm_host_map virtual_apic_map;
    > - struct page *pi_desc_page;
    > + struct kvm_host_map pi_desc_map;
    >
    > struct kvm_host_map msr_bitmap_map;
    >
    > --
    > 2.7.4
    >

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