| Message ID | 20240726235234.228822-51-seanjc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: Stop grabbing references to PFNMAP'd pages | expand |
On 7/27/24 01:51, Sean Christopherson wrote: > 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; Even if you don't use it, call the out argument "writable". Paolo > > /* 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
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
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(-)