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AJvYcCUi9SnJY3RzB7iFJ308jqkZI1qdA2wInUnJjUENVKWf7RU6Vl71D4NRwva5+k6QXms94wTtGbTlXuSeMtLG@vger.kernel.org X-Gm-Message-State: AOJu0YwrAbnsjs19lwZqPi58Z/vBk5HQ06yTauZqzXg5a+SKBZjWvako Lb7vkUcEyyiRe3lWT6AHXejq/No7jajHG64FO4Ic7TWQtqDM4wKHyobSjWfraBehdL9N1mTfYA= = X-Google-Smtp-Source: AGHT+IFjfxf6/c4YGYpRR8ebQgMC7nETbgoP7o3HpJ1E0q7VHYEiUY/Sncl1PhAsgk21ab/L2t0C6VGu3g== X-Received: from wrps2.prod.google.com ([2002:adf:f802:0:b0:399:7a0a:493f]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:18a8:b0:391:4559:876a with SMTP id ffacd0b85a97d-39ad1794cd7mr8199077f8f.46.1743175898942; Fri, 28 Mar 2025 08:31:38 -0700 (PDT) Date: Fri, 28 Mar 2025 15:31:28 +0000 In-Reply-To: <20250328153133.3504118-1-tabba@google.com> Precedence: bulk X-Mailing-List: linux-arm-msm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250328153133.3504118-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.472.ge94155a9ec-goog Message-ID: <20250328153133.3504118-3-tabba@google.com> Subject: [PATCH v7 2/7] KVM: guest_memfd: Introduce kvm_gmem_get_pfn_locked(), which retains the folio lock From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, david@redhat.com, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, tabba@google.com Create a new variant of kvm_gmem_get_pfn(), which retains the folio lock if it returns successfully. This is needed in subsequent patches to protect against races when checking whether a folio can be shared with the host. Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 11 +++++++++++ virt/kvm/guest_memfd.c | 27 ++++++++++++++++++++------- 2 files changed, 31 insertions(+), 7 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index ec3bedc18eab..bc73d7426363 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2535,6 +2535,9 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, struct page **page, int *max_order); +int kvm_gmem_get_pfn_locked(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, struct page **page, + int *max_order); #else static inline int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, @@ -2544,6 +2547,14 @@ static inline int kvm_gmem_get_pfn(struct kvm *kvm, KVM_BUG_ON(1, kvm); return -EIO; } +static inline int kvm_gmem_get_pfn_locked(struct kvm *kvm, + struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, + struct page **page, int *max_order) +{ + KVM_BUG_ON(1, kvm); + return -EIO; +} #endif /* CONFIG_KVM_PRIVATE_MEM */ #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 844e70c82558..ac6b8853699d 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -802,9 +802,9 @@ static struct folio *__kvm_gmem_get_pfn(struct file *file, return folio; } -int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, - gfn_t gfn, kvm_pfn_t *pfn, struct page **page, - int *max_order) +int kvm_gmem_get_pfn_locked(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, struct page **page, + int *max_order) { pgoff_t index = kvm_gmem_get_index(slot, gfn); struct file *file = kvm_gmem_get_file(slot); @@ -824,17 +824,30 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, if (!is_prepared) r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); - folio_unlock(folio); - - if (!r) + if (!r) { *page = folio_file_page(folio, index); - else + } else { + folio_unlock(folio); folio_put(folio); + } out: fput(file); return r; } +EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn_locked); + +int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, struct page **page, + int *max_order) +{ + int r = kvm_gmem_get_pfn_locked(kvm, slot, gfn, pfn, page, max_order); + + if (!r) + unlock_page(*page); + + return r; +} EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn); #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM