[PATCH v12 50/84] KVM: VMX: Use __kvm_faultin_page() to get APIC access page/pfn

Sean Christopherson
2024-07-27T00:20:14Z

Use __kvm_faultin_page() get the APIC access page so that KVM can
precisely release the refcounted page, i.e. to remove yet another user
of kvm_pfn_to_refcounted_page(). While the path isn't handling a guest
page fault, the semantics are effectively the same; KVM just happens to
be mapping the pfn into a VMCS field instead of a secondary MMU.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/vmx.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 30032585f7dc..b109bd282a52 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6786,8 +6786,10 @@ void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
struct kvm *kvm = vcpu->kvm;
struct kvm_memslots *slots = kvm_memslots(kvm);
struct kvm_memory_slot *slot;
+ struct page *refcounted_page;
unsigned long mmu_seq;
kvm_pfn_t pfn;
+ bool ign;

/* Defer reload until vmcs01 is the current VMCS. */
if (is_guest_mode(vcpu)) {
@@ -6823,7 +6825,7 @@ void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
* controls the APIC-access page memslot, and only deletes the memslot
* if APICv is permanently inhibited, i.e. the memslot won't reappear.
*/
- pfn = gfn_to_pfn_memslot(slot, gfn);
+ pfn = __kvm_faultin_pfn(slot, gfn, FOLL_WRITE, &ign, &refcounted_page);
if (is_error_noslot_pfn(pfn))
return;

@@ -6834,10 +6836,13 @@ void vmx_set_apic_access_page_addr(struct kvm_vcpu *vcpu)
vmcs_write64(APIC_ACCESS_ADDR, pfn_to_hpa(pfn));

/*
- * Do not pin apic access page in memory, the MMU notifier
- * will call us again if it is migrated or swapped out.
+ * Do not pin the APIC access page in memory so that it can be freely
+ * migrated, the MMU notifier will call us again if it is migrated or
+ * swapped out. KVM backs the memslot with anonymous memory, the pfn
+ * should always point at a refcounted page (if the pfn is valid).
*/
- kvm_release_pfn_clean(pfn);
+ if (!WARN_ON_ONCE(!refcounted_page))
+ kvm_release_page_clean(refcounted_page);

/*
* No need for a manual TLB flush at this point, KVM has already done a