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AJvYcCWzbeW3kA0vwBLOHJbHKeKr7vZp2dCUfbFsUJXLgdrnjwdS2Ti2LF2Jm+lGDy+eEfo4pPOy3PhfZ1wiBSP4@vger.kernel.org X-Gm-Message-State: AOJu0YzfEQ9GsH1WP1YqZPqvNr2r66QIoVQyUTj9PofbudjH3/ySgZtB KJCZ1BC3Rc/3KcoAocr9eAxHjbhTYNx4TkVMTex82SQVWKnJ2lY4YgfU3gYEHu2EUIeGUCFzMQ= = X-Google-Smtp-Source: AGHT+IFJwsaDfsra9si5hSwL5TQTTo4RhmMq+iKHIyBjxFdz3SDsa44kizohADHJBxPg0EWk39rrAlUrlw== X-Received: from fuad.c.googlers.com ([fda3:e722:ac3:cc00:28:9cb1:c0a8:1613]) (user=tabba job=sendgmr) by 2002:a17:906:e207:b0:a89:ee2b:e2dd with SMTP id a640c23a62f3a-a998d31c253mr128966b.12.1728550780668; Thu, 10 Oct 2024 01:59:40 -0700 (PDT) Date: Thu, 10 Oct 2024 09:59:22 +0100 In-Reply-To: <20241010085930.1546800-1-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: <20241010085930.1546800-1-tabba@google.com> X-Mailer: git-send-email 2.47.0.rc0.187.ge670bccf7e-goog Message-ID: <20241010085930.1546800-4-tabba@google.com> Subject: [PATCH v3 03/11] 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, yu.c.zhang@linux.intel.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, 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 in order to protect against races when checking whether a folio can be mapped by the host. Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 11 ++++++++++ virt/kvm/guest_memfd.c | 45 +++++++++++++++++++++++++++++++--------- 2 files changed, 46 insertions(+), 10 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index db567d26f7b9..acf85995b582 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -2464,6 +2464,9 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn) #ifdef CONFIG_KVM_PRIVATE_MEM int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, kvm_pfn_t *pfn, int *max_order); +int kvm_gmem_get_pfn_locked(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, int *max_order); + #else static inline int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, gfn_t gfn, @@ -2472,6 +2475,14 @@ 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, 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 4d3ba346c415..f414646c475b 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -714,34 +714,59 @@ __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot, return folio; } -int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot, - gfn_t gfn, kvm_pfn_t *pfn, int *max_order) +static int +kvm_gmem_get_pfn_folio_locked(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, int *max_order, + struct folio **folio) { struct file *file = kvm_gmem_get_file(slot); - struct folio *folio; bool is_prepared = false; int r = 0; if (!file) return -EFAULT; - folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, &is_prepared, max_order); - if (IS_ERR(folio)) { - r = PTR_ERR(folio); + *folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, &is_prepared, max_order); + if (IS_ERR(*folio)) { + r = PTR_ERR(*folio); goto out; } if (!is_prepared) - r = kvm_gmem_prepare_folio(kvm, slot, gfn, folio); + r = kvm_gmem_prepare_folio(kvm, slot, gfn, *folio); - folio_unlock(folio); - if (r < 0) - folio_put(folio); + if (r) { + folio_unlock(*folio); + folio_put(*folio); + } out: fput(file); return r; } + +int kvm_gmem_get_pfn_locked(struct kvm *kvm, struct kvm_memory_slot *slot, + gfn_t gfn, kvm_pfn_t *pfn, int *max_order) +{ + struct folio *folio; + + return kvm_gmem_get_pfn_folio_locked(kvm, slot, gfn, pfn, max_order, &folio); + +} +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, int *max_order) +{ + struct folio *folio; + int r; + + r = kvm_gmem_get_pfn_folio_locked(kvm, slot, gfn, pfn, max_order, &folio); + if (!r) + folio_unlock(folio); + + return r; +} EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn); #ifdef CONFIG_KVM_GENERIC_PRIVATE_MEM