[PATCH v12 30/84] KVM: nVMX: Mark vmcs12's APIC access page dirty when unmapping

Sean Christopherson
2024-07-27T00:05:12Z

Mark the APIC access page as dirty when unmapping it from KVM. The fact
that the page _shouldn't_ be written doesn't guarantee the page _won't_ be
written. And while the contents are likely irrelevant, the values _are_
visible to the guest, i.e. dropping writes would be visible to the guest
(though obviously highly unlikely to be problematic in practice).

Marking the map dirty will allow specifying the write vs. read-only when
*mapping* the memory, which in turn will allow creating read-only maps.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/nested.c | 7 +------
1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8d05d1d9f544..3096f6f5ecdb 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -318,12 +318,7 @@ static void nested_put_vmcs12_pages(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);

- /*
- * Unpin physical memory we referred to in the vmcs02. The APIC access
- * page's backing page (yeah, confusing) shouldn't actually be accessed,
- * and if it is written, the contents are irrelevant.
- */
- kvm_vcpu_unmap(vcpu, &vmx->nested.apic_access_page_map, false);
+ kvm_vcpu_unmap(vcpu, &vmx->nested.apic_access_page_map, true);
kvm_vcpu_unmap(vcpu, &vmx->nested.virtual_apic_map, true);
kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map, true);
vmx->nested.pi_desc = NULL;