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AJvYcCVWxwRUcTXrhn6yxPrXGIk+M3kQk7FYxP6aGDLJ4r8MFIVRguY2nP/brwz3RxLjMmMITtm8+iDkTQ==@kvack.org X-Gm-Message-State: AOJu0YxGg3fKfy87NUhQcSA0ciaE1iekbmMV6FQ9KkR+KOPV91oGtNlY PhMwWWszD/KfN0/78YK+PLjsx9gtyWOsNbPaEUBQHjpcgNZ1atiP9VLhalix+fs8rz8qoeOJFg= = X-Google-Smtp-Source: AGHT+IFmHd9CyHM8TklDJLl/Zwd2hd7SSZMAwOsu5I2BqW7wDeKi1D4jAZf4EsiqIdJLp0CMxLUAq5zQDw== X-Received: from wmcn4.prod.google.com ([2002:a05:600c:c0c4:b0:43c:fae1:8125]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:5103:b0:43d:fa:1f9a with SMTP id 5b1f17b1804b1-43d3ba2971emr26297695e9.30.1742314852121; Tue, 18 Mar 2025 09:20:52 -0700 (PDT) Date: Tue, 18 Mar 2025 16:20:41 +0000 In-Reply-To: <20250318162046.4016367-1-tabba@google.com> Mime-Version: 1.0 References: <20250318162046.4016367-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.rc1.451.g8f38331e32-goog Message-ID: <20250318162046.4016367-3-tabba@google.com> Subject: [PATCH v6 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, tabba@google.com X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6CCC440003 X-Stat-Signature: uuzh8nddd566awu7n4kp8z5paafge63d X-HE-Tag: 1742314853-395977 X-HE-Meta: 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 1ua6evMd 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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