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AJvYcCVQNZp57oHZ3ImD08/HhozsR/olsDrQ7Rq24aI8TTyBuLfZ180sVJaiA3yH7GXuHaeumosKXQeNp8DIIttC@vger.kernel.org X-Gm-Message-State: AOJu0Yx2Lqq3l7QOuEPLHMivzI65Icc9NNPSIneHiRpO5F9gUg2tPaoh zIPUnC4AIqhdyMIjZHRkhokJSUS2YU1L+1tBWO9e8S1k8dk8aUThk8A/7jn3yP338DaozU2fjD7 1Tw== X-Google-Smtp-Source: AGHT+IHm2QpLuppopnrLbiEdYMpqiHL9Z+DX8uPYQe0kFHM4Ap6KdDfZYYe7oYWFnkWPUHOflJMK8/QPyw== X-Received: from wmbbi21.prod.google.com ([2002:a05:600c:3d95:b0:43c:ebbe:4bce]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4f43:b0:442:e0e0:250 with SMTP id 5b1f17b1804b1-44c933ed7efmr124297415e9.29.1748368984939; Tue, 27 May 2025 11:03:04 -0700 (PDT) Date: Tue, 27 May 2025 19:02:38 +0100 In-Reply-To: <20250527180245.1413463-1-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: <20250527180245.1413463-1-tabba@google.com> X-Mailer: git-send-email 2.49.0.1164.gab81da1b16-goog Message-ID: <20250527180245.1413463-10-tabba@google.com> Subject: [PATCH v10 09/16] KVM: guest_memfd: Track shared memory support in memslot 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, ira.weiny@intel.com, tabba@google.com Content-Type: text/plain; charset="UTF-8" Track whether a guest_memfd-backed memslot supports shared memory within the memslot itself, using the flags field. The top half of memslot flags is reserved for internal use in KVM. Add a flag there to track shared memory support. This saves the caller from having to check the guest_memfd-backed file for this support, a potentially more expensive operation due to the need to get/put the file. Suggested-by: David Hildenbrand Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 11 ++++++++++- virt/kvm/guest_memfd.c | 8 ++++++-- 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index ba83547e62b0..edb3795a64b9 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -54,7 +54,8 @@ * used in kvm, other bits are visible for userspace which are defined in * include/uapi/linux/kvm.h. */ -#define KVM_MEMSLOT_INVALID (1UL << 16) +#define KVM_MEMSLOT_INVALID (1UL << 16) +#define KVM_MEMSLOT_SUPPORTS_SHARED (1UL << 17) /* * Bit 63 of the memslot generation number is an "update in-progress flag", @@ -2502,6 +2503,14 @@ static inline void kvm_prepare_memory_fault_exit(struct kvm_vcpu *vcpu, vcpu->run->memory_fault.flags |= KVM_MEMORY_EXIT_FLAG_PRIVATE; } +static inline bool kvm_gmem_memslot_supports_shared(const struct kvm_memory_slot *slot) +{ + if (!IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM)) + return false; + + return slot->flags & KVM_MEMSLOT_SUPPORTS_SHARED; +} + #ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn) { diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 5d34712f64fc..9ded8d5139ee 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -555,6 +555,7 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, loff_t size = slot->npages << PAGE_SHIFT; unsigned long start, end; struct kvm_gmem *gmem; + bool supports_shared; struct inode *inode; struct file *file; int r = -EINVAL; @@ -578,8 +579,9 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, offset + size > i_size_read(inode)) goto err; - if (kvm_gmem_supports_shared(inode) && - !kvm_arch_supports_gmem_shared_mem(kvm)) + supports_shared = kvm_gmem_supports_shared(inode); + + if (supports_shared && !kvm_arch_supports_gmem_shared_mem(kvm)) goto err; filemap_invalidate_lock(inode->i_mapping); @@ -600,6 +602,8 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, */ WRITE_ONCE(slot->gmem.file, file); slot->gmem.pgoff = start; + if (supports_shared) + slot->flags |= KVM_MEMSLOT_SUPPORTS_SHARED; xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); filemap_invalidate_unlock(inode->i_mapping); -- 2.49.0.1164.gab81da1b16-goog