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AJvYcCUZqrJWxzvzjWzMf7Vh/Q4PAILIjufGB/p33k71hF/+Bsw8IHbeu24vSFN1DfSDyAihMc1FP/M=@lists.linux.dev X-Gm-Message-State: AOJu0YwnhCuUcQWhg3ef6O21CpjGZKfYFS8eFDmKwcxXneE80/2DAOyn UPDPv2/7UNHa0bMGBG4wneZ3P+mWXPwPB1yUb/YuOzJoezFljSwm1ohaGbVk53Ca0qEHdh3URAZ 94w== X-Google-Smtp-Source: AGHT+IEQJp1MO1Qe/j84OGHbzIcWoKPAALChchZ3KOUi17k1TGhTtWrYDnxKKdMZ3WUIwsAkbY5Mkj9wdw== X-Received: from wmbjh9.prod.google.com ([2002:a05:600c:a089:b0:450:cb8f:62cc]) (user=tabba job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:24c7:b0:39c:30cd:352c with SMTP id ffacd0b85a97d-3a558a9ae6amr2386549f8f.8.1749648831011; Wed, 11 Jun 2025 06:33:51 -0700 (PDT) Date: Wed, 11 Jun 2025 14:33:21 +0100 In-Reply-To: <20250611133330.1514028-1-tabba@google.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250611133330.1514028-1-tabba@google.com> X-Mailer: git-send-email 2.50.0.rc0.642.g800a2b2222-goog Message-ID: <20250611133330.1514028-10-tabba@google.com> Subject: [PATCH v12 09/18] 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, 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" Add a new internal flag in the top half of memslot->flags to track when a guest_memfd-backed slot supports shared memory, which is reserved for internal use in KVM. This avoids repeatedly checking the underlying guest_memfd file for shared memory support, which requires taking a reference on the file. Reviewed-by: Gavin Shan 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 6b63556ca150..bba7d2c14177 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_GMEM_SHARED (1UL << 17) /* * Bit 63 of the memslot generation number is an "update in-progress flag", @@ -2525,6 +2526,14 @@ 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_GMEM_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 06616b6b493b..73b0aa2bc45f 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_shared(inode)) + slot->flags |= KVM_MEMSLOT_SUPPORTS_GMEM_SHARED; xa_store_range(&gmem->bindings, start, end - 1, slot, GFP_KERNEL); filemap_invalidate_unlock(inode->i_mapping); -- 2.50.0.rc0.642.g800a2b2222-goog