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Tue, 30 Jul 2024 01:58:35 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHAOIIltVQdWTS+wB0eMPC1Ma/f+US5vc2+G0XsatRnSCbICJZcTeRE4zXEmrhssvwMjnoa3g== X-Received: by 2002:a19:6a0e:0:b0:52e:fa14:cc96 with SMTP id 2adb3069b0e04-5309b27e54dmr7004170e87.34.1722329914765; Tue, 30 Jul 2024 01:58:34 -0700 (PDT) Received: from [192.168.10.47] ([151.95.101.29]) by smtp.googlemail.com with ESMTPSA id a640c23a62f3a-a7acab23125sm616347566b.1.2024.07.30.01.58.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 30 Jul 2024 01:58:34 -0700 (PDT) Message-ID: <96df1dd5-cc31-4e84-84fd-ea75b4800be8@redhat.com> Date: Tue, 30 Jul 2024 10:58:32 +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 48/84] KVM: Move x86's API to release a faultin page to common KVM 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> <20240726235234.228822-49-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: > Move KVM x86's helper that "finishes" the faultin process to common KVM > so that the logic can be shared across all architectures. Note, not all > architectures implement a fast page fault path, but the gist of the > comment applies to all architectures. > > Signed-off-by: Sean Christopherson > --- > arch/x86/kvm/mmu/mmu.c | 24 ++---------------------- > include/linux/kvm_host.h | 26 ++++++++++++++++++++++++++ > 2 files changed, 28 insertions(+), 22 deletions(-) > > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 95beb50748fc..2a0cfa225c8d 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -4323,28 +4323,8 @@ static u8 kvm_max_private_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, > static void kvm_mmu_finish_page_fault(struct kvm_vcpu *vcpu, > struct kvm_page_fault *fault, int r) > { > - lockdep_assert_once(lockdep_is_held(&vcpu->kvm->mmu_lock) || > - r == RET_PF_RETRY); > - > - if (!fault->refcounted_page) > - return; > - > - /* > - * If the page that KVM got from the *primary MMU* is writable, and KVM > - * installed or reused a SPTE, mark the page/folio dirty. Note, this > - * may mark a folio dirty even if KVM created a read-only SPTE, e.g. if > - * the GFN is write-protected. Folios can't be safely marked dirty > - * outside of mmu_lock as doing so could race with writeback on the > - * folio. As a result, KVM can't mark folios dirty in the fast page > - * fault handler, and so KVM must (somewhat) speculatively mark the > - * folio dirty if KVM could locklessly make the SPTE writable. > - */ > - if (r == RET_PF_RETRY) > - kvm_release_page_unused(fault->refcounted_page); > - else if (!fault->map_writable) > - kvm_release_page_clean(fault->refcounted_page); > - else > - kvm_release_page_dirty(fault->refcounted_page); > + kvm_release_faultin_page(vcpu->kvm, fault->refcounted_page, > + r == RET_PF_RETRY, fault->map_writable); Does it make sense to move RET_PF_* to common code, and avoid a bool argument here? Paolo > } > > static int kvm_mmu_faultin_pfn_private(struct kvm_vcpu *vcpu, > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 9d2a97eb30e4..91341cdc6562 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1216,6 +1216,32 @@ static inline void kvm_release_page_unused(struct page *page) > void kvm_release_page_clean(struct page *page); > void kvm_release_page_dirty(struct page *page); > > +static inline void kvm_release_faultin_page(struct kvm *kvm, struct page *page, > + bool unused, bool dirty) > +{ > + lockdep_assert_once(lockdep_is_held(&kvm->mmu_lock) || unused); > + > + if (!page) > + return; > + > + /* > + * If the page that KVM got from the *primary MMU* is writable, and KVM > + * installed or reused a SPTE, mark the page/folio dirty. Note, this > + * may mark a folio dirty even if KVM created a read-only SPTE, e.g. if > + * the GFN is write-protected. Folios can't be safely marked dirty > + * outside of mmu_lock as doing so could race with writeback on the > + * folio. As a result, KVM can't mark folios dirty in the fast page > + * fault handler, and so KVM must (somewhat) speculatively mark the > + * folio dirty if KVM could locklessly make the SPTE writable. > + */ > + if (unused) > + kvm_release_page_unused(page); > + else if (dirty) > + kvm_release_page_dirty(page); > + else > + kvm_release_page_clean(page); > +} > + > kvm_pfn_t kvm_lookup_pfn(struct kvm *kvm, gfn_t gfn); > kvm_pfn_t __kvm_faultin_pfn(const struct kvm_memory_slot *slot, gfn_t gfn, > unsigned int foll, bool *writable,