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AJvYcCX36SSj/3gIAagO+y/rAfK4yZWsd27gDYqqOsrz5mr5A3TH413lvlA16rIY0SMk4GBdK+LgOpZUAg==@kvack.org X-Gm-Message-State: AOJu0YzWx2kFZL4e+GQ1LrZbTD6Fj7FCJ7AQDnuit6XGP9ZZ4TJhJxP1 y03hjM7QtI8ht3CAaqWVLLTfEiRdSYDhvDKuIHdAEnwlGVR3LJT/qtDVqqvWRx9fCUT+HfvVpB5 CVg== X-Google-Smtp-Source: AGHT+IE21fhaeICe83jRxJ9PmfXWuTRh00VmTrToJooYUCyNgKLMGI0nhgD6QdhoopuIJeihgPQK1UPb+Q== X-Received: from wmbfp9.prod.google.com ([2002:a05:600c:6989:b0:456:3cf:1e95]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:26cc:b0:3a4:d4cd:b06 with SMTP id ffacd0b85a97d-3b60e50ff10mr6053820f8f.34.1752769661545; Thu, 17 Jul 2025 09:27:41 -0700 (PDT) Date: Thu, 17 Jul 2025 17:27:19 +0100 In-Reply-To: <20250717162731.446579-1-tabba@google.com> Mime-Version: 1.0 References: <20250717162731.446579-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250717162731.446579-10-tabba@google.com> Subject: [PATCH v15 09/21] 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-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2AFC0A0004 X-Stat-Signature: 7rsodt6n5fcyc8wun9phqsgnnhno9bax X-HE-Tag: 1752769662-105037 X-HE-Meta: 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 rgj67ATX 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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 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 9ac21985f3b5..d2218ec57ceb 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", @@ -2536,6 +2537,14 @@ 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_GMEM_SUPPORTS_MMAP)) + 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 07a4b165471d..2b00f8796a15 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -592,6 +592,8 @@ 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); -- 2.50.0.727.gbf7dc18ff4-goog