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Tue, 30 Jul 2024 01:59:59 -0700 (PDT) X-Google-Smtp-Source: AGHT+IF1CX9fuid97Fo9k/P7XEAx/O03KlRJUJxp6LS6LdYujPfua6G8Lket79YT5PUqIa4JM4vZ8g== X-Received: by 2002:ac2:4bd4:0:b0:530:ac41:4ee with SMTP id 2adb3069b0e04-530ac410772mr853087e87.24.1722329999379; Tue, 30 Jul 2024 01:59:59 -0700 (PDT) Received: from [192.168.10.47] ([151.95.101.29]) by smtp.googlemail.com with ESMTPSA id 4fb4d7f45d1cf-5ac63590d76sm7021589a12.24.2024.07.30.01.59.57 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jul 2024 01:59:58 -0700 (PDT) Message-ID: Date: Tue, 30 Jul 2024 10:59:57 +0200 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 50/84] KVM: VMX: Use __kvm_faultin_page() to get APIC access page/pfn To: Sean Christopherson , Marc Zyngier , Oliver Upton , Tianrui Zhao , Bibo Mao , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Christian Borntraeger , Janosch Frank , Claudio Imbrenda Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, David Matlack , David Stevens References: <20240726235234.228822-1-seanjc@google.com> <20240726235234.228822-51-seanjc@google.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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 > --- > 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