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AJvYcCXfIPV5kv1IjVGJ4qmMOy1G3hLERcR6naLHqdoNAP4EBVZQOF3QKqRglIFjs9hV7S/6A4VdSJoW0A==@kvack.org X-Gm-Message-State: AOJu0YxmQJ8Gfv5QryDSiUFCm6FEboOLzg4rdItJ5UbyYqxrgRV8BDR5 DnngVXjxSaQN4mXILhmIcAs0sPyohvARJTEKfNqN2gc5rTLxJQh+Cl2gR2WnbQiWGDYhaUUT0BR 7yg== X-Google-Smtp-Source: AGHT+IFb2OSH7lEKwhbKN8+t42ZlOCnkfwV4bEknRLarq2YT9adSgiVMvCqHjEbxvfjY3zoBqSDXrJRWaQ== X-Received: from wrpf9.prod.google.com ([2002:adf:f449:0:b0:3b2:5edb:a37b]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:2086:b0:3a5:67d5:a400 with SMTP id ffacd0b85a97d-3b5f18b3eaemr14590340f8f.33.1752572050760; Tue, 15 Jul 2025 02:34:10 -0700 (PDT) Date: Tue, 15 Jul 2025 10:33:38 +0100 In-Reply-To: <20250715093350.2584932-1-tabba@google.com> Mime-Version: 1.0 References: <20250715093350.2584932-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.727.gbf7dc18ff4-goog Message-ID: <20250715093350.2584932-10-tabba@google.com> Subject: [PATCH v14 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: 283D01C0005 X-Stat-Signature: tz8qpzbusmrwib4efwk8seq9aoq3hreq X-HE-Tag: 1752572051-273130 X-HE-Meta: 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 cq3OyKae 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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. This flag tracks when a guest_memfd-backed memory slot supports host userspace mmap operations. It's strictly for KVM's internal use. 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