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AJvYcCVH5u7BreRo3zoiOaNX/r7KwcXZJY+BNRuolEvtkjmhlOseWTlLM1rMFCxN8330z36KmKlqjNMxVw==@kvack.org X-Gm-Message-State: AOJu0Yx349QYKg90pb64JT7r3NdE+PERjwxydhcPN7IQUXWGFmPBd27A Y6jGRIVtvbuy6woAFgPx9Eh4wbPCZtuV/FypTMaOKz38BUcEtd2VubFGRw1Yn+7gjsGFnVGwusC iB7y9yRs2xGFd+UCNDRDw5kWxKw== X-Google-Smtp-Source: AGHT+IFw3NgbtgTZNOENDz2gBk436xq9cSXbkfHKeXAn9g3NU8+yq1Zt0gAdx01FZUaxcKcWB1HdYR90j/8QeZ03Wg== X-Received: from plar10.prod.google.com ([2002:a17:902:c7ca:b0:27e:4187:b4d3]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ce8d:b0:290:52aa:7291 with SMTP id d9443c01a7336-290cba41df2mr57184855ad.53.1760731965412; Fri, 17 Oct 2025 13:12:45 -0700 (PDT) Date: Fri, 17 Oct 2025 13:11:51 -0700 In-Reply-To: Mime-Version: 1.0 References: X-Mailer: git-send-email 2.51.0.858.gf9c4a03a3a-goog Message-ID: <98bee9fff5dcd28a378d81f8b52a561bca8e7362.1760731772.git.ackerleytng@google.com> Subject: [RFC PATCH v1 10/37] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs From: Ackerley Tng To: cgroups@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org Cc: ackerleytng@google.com, akpm@linux-foundation.org, binbin.wu@linux.intel.com, bp@alien8.de, brauner@kernel.org, chao.p.peng@intel.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@intel.com, dave.hansen@linux.intel.com, david@redhat.com, dmatlack@google.com, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, haibo1.xu@intel.com, hannes@cmpxchg.org, hch@infradead.org, hpa@zytor.com, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgg@ziepe.ca, jgowans@amazon.com, jhubbard@nvidia.com, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maobibo@loongson.cn, mathieu.desnoyers@efficios.com, maz@kernel.org, mhiramat@kernel.org, mhocko@kernel.org, mic@digikod.net, michael.roth@amd.com, mingo@redhat.com, mlevitsk@redhat.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, peterx@redhat.com, pgonda@google.com, prsampat@amd.com, pvorel@suse.cz, qperret@google.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, rostedt@goodmis.org, roypat@amazon.co.uk, rppt@kernel.org, seanjc@google.com, shakeel.butt@linux.dev, shuah@kernel.org, steven.price@arm.com, steven.sistare@oracle.com, suzuki.poulose@arm.com, tabba@google.com, tglx@linutronix.de, thomas.lendacky@amd.com, vannapurve@google.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, wyihan@google.com, xiaoyao.li@intel.com, yan.y.zhao@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: B55FA40004 X-Stat-Signature: fpor6rmszs3ggqxgd7w1dbe7kx9cuijd X-Rspam-User: X-HE-Tag: 1760731966-112032 X-HE-Meta: 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 SOegdvTf 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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: From: Sean Christopherson Now that guest_memfd supports tracking private vs. shared within gmem itself, allow userspace to specify INIT_SHARED on a guest_memfd instance for x86 Confidential Computing (CoCo) VMs, so long as per-VM attributes are disabled, i.e. when it's actually possible for a guest_memfd instance to contain shared memory. Signed-off-by: Sean Christopherson --- arch/x86/kvm/x86.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 5e38c4c9cf63c..4ad451982380e 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -13941,14 +13941,13 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu) } #ifdef CONFIG_KVM_GUEST_MEMFD -/* - * KVM doesn't yet support initializing guest_memfd memory as shared for VMs - * with private memory (the private vs. shared tracking needs to be moved into - * guest_memfd). - */ bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm) { - return !kvm_arch_has_private_mem(kvm); + /* + * INIT_SHARED isn't supported if the memory attributes are per-VM, + * in which case guest_memfd can _only_ be used for private memory. + */ + return !vm_memory_attributes || !kvm_arch_has_private_mem(kvm); } #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE -- 2.51.0.858.gf9c4a03a3a-goog