[PATCH v12 49/84] KVM: VMX: Hold mmu_lock until page is released when updating APIC access page

[Sean Christopherson]

Hold mmu_lock across kvm_release_pfn_clean() when refreshing the APIC
access page address to ensure that KVM doesn't mark a page/folio as
accessed after it has been unmapped.  Practically speaking marking a folio
accesses is benign in this scenario, as KVM does hold a reference (it's
really just marking folios dirty that is problematic), but there's no
reason not to be paranoid (moving the APIC access page isn't a hot path),
and no reason to be different from other mmu_notifier-protected flows in
KVM.

Signed-off-by: Sean Christopherson <sea...@google.com>
---
 arch/x86/kvm/vmx/vmx.c | 21 +++++++++------------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f18c2d8c7476..30032585f7dc 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6828,25 +6828,22 @@ void vmx_set_apic_access_page_addr(struct kvm_vcpu 
*vcpu)
                return;
 
        read_lock(&vcpu->kvm->mmu_lock);
-       if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn)) {
+       if (mmu_invalidate_retry_gfn(kvm, mmu_seq, gfn))
                kvm_make_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu);
-               read_unlock(&vcpu->kvm->mmu_lock);
-               goto out;
-       }
+       else
+               vmcs_write64(APIC_ACCESS_ADDR, pfn_to_hpa(pfn));
 
-       vmcs_write64(APIC_ACCESS_ADDR, pfn_to_hpa(pfn));
-       read_unlock(&vcpu->kvm->mmu_lock);
-
-       /*
-        * No need for a manual TLB flush at this point, KVM has already done a
-        * flush if there were SPTEs pointing at the previous page.
-        */
-out:
        /*
         * Do not pin apic access page in memory, the MMU notifier
         * will call us again if it is migrated or swapped out.
         */
        kvm_release_pfn_clean(pfn);
+
+       /*
+        * No need for a manual TLB flush at this point, KVM has already done a
+        * flush if there were SPTEs pointing at the previous page.
+        */
+       read_unlock(&vcpu->kvm->mmu_lock);
 }
 
 void vmx_hwapic_isr_update(int max_isr)
-- 
2.46.0.rc1.232.g9752f9e123-goog