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AJvYcCUoUbA+M5NFd3KTw2ALIbu6tzwkNY6FHYPc6cyJwLpcCPwwjjrsyQP9AMEcfUPpRS9CqMfI8fJGJA==@kvack.org X-Gm-Message-State: AOJu0YxtYom4rY/J4HLBBlYkHvSIFzNbZpkkgMKS0LAbKNB2N/1rKjOd 8/Wha5PQzo4ixaVVY+FJ3I3Xfc6cIqnzV9IiXaPnD8IYZ5AuomiM7YK3DC0PvV80NPXnLxRuCY+ 7pg== X-Google-Smtp-Source: AGHT+IF9GujN7e5PEevnbfhJVmv/zauyrMQPlcffBVgGfUsoXqo1KZ7TOBa+t16TTquYqLmxApIIyf6F5Q== X-Received: from wmqe11.prod.google.com ([2002:a05:600c:4e4b:b0:453:86cc:7393]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:4f12:b0:456:f1e:205c with SMTP id 5b1f17b1804b1-45868c74efcmr21231745e9.4.1753267646461; Wed, 23 Jul 2025 03:47:26 -0700 (PDT) Date: Wed, 23 Jul 2025 11:47:03 +0100 In-Reply-To: <20250723104714.1674617-1-tabba@google.com> Mime-Version: 1.0 References: <20250723104714.1674617-1-tabba@google.com> X-Mailer: git-send-email 2.50.1.470.g6ba607880d-goog Message-ID: <20250723104714.1674617-12-tabba@google.com> Subject: [PATCH v16 11/22] KVM: guest_memfd: Track guest_memfd mmap support in memslot From: Fuad Tabba To: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev 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" X-Rspamd-Queue-Id: D70161C000A X-Stat-Signature: wjjwjj5w9pknbs7axcyudh9zk96m94g7 X-Rspam-User: X-Rspamd-Server: rspam07 X-HE-Tag: 1753267647-63870 X-HE-Meta: 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 Tuoq+SBT 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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: Add a new internal flag, KVM_MEMSLOT_GMEM_ONLY, to the top half of memslot->flags (which makes it strictly for KVM's internal use). This flag tracks when a guest_memfd-backed memory slot supports host userspace mmap operations, which implies that all memory, not just private memory for CoCo VMs, is consumed through guest_memfd: "gmem only". This optimization avoids repeatedly checking the underlying guest_memfd file for mmap support, which would otherwise require taking and releasing a reference on the file for each check. By caching this information directly in the memslot, we reduce overhead and simplify the logic involved in handling guest_memfd-backed pages for host mappings. Reviewed-by: Gavin Shan Reviewed-by: Shivank Garg Reviewed-by: Xiaoyao Li Acked-by: David Hildenbrand Suggested-by: David Hildenbrand Signed-off-by: Fuad Tabba --- include/linux/kvm_host.h | 11 ++++++++++- virt/kvm/guest_memfd.c | 2 ++ 2 files changed, 12 insertions(+), 1 deletion(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 26bad600f9fa..8b47891adca1 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_GMEM_ONLY (1UL << 17) /* * Bit 63 of the memslot generation number is an "update in-progress flag", @@ -2490,6 +2491,14 @@ 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_memslot_is_gmem_only(const struct kvm_memory_slot *slot) +{ + if (!IS_ENABLED(CONFIG_KVM_GUEST_MEMFD)) + return false; + + return slot->flags & KVM_MEMSLOT_GMEM_ONLY; +} + #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 67e7cd7210ef..d5b445548af4 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -578,6 +578,8 @@ int kvm_gmem_bind(struct kvm *kvm, struct kvm_memory_slot *slot, */ WRITE_ONCE(slot->gmem.file, file); slot->gmem.pgoff = start; + if (kvm_gmem_supports_mmap(inode)) + slot->flags |= KVM_MEMSLOT_GMEM_ONLY; xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); filemap_invalidate_unlock(inode->i_mapping); -- 2.50.1.470.g6ba607880d-goog