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AHgh+RooagbY2tjslNH/B0KNwq4twngggJGm06fELaMBVg+86y5nmRjowSh60awm1o0aKklhkMIK+QJYYbrR@lists.linux.dev X-Gm-Message-State: AFuF++ltmuzHIXpRUDQ5Q9eW9Il8Ph7510f5nY5+CXghCwbDjjAybsFv 1hL306DnMkQFz1caiDmMU5IoVxjZTWLfDIU7LMheoS5de63phrSG/1+o79gbmBiewtTP2LyDM+p p1oVJpkX88dH0hWefafrrKpE0Ew== X-Received: from plco20.prod.google.com ([2002:a17:902:e294:b0:2c9:b703:3bfb]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:2c03:b0:2d6:ee6b:1b08 with SMTP id d9443c01a7336-2d707a2f363mr88247725ad.3.1787735928419; Wed, 26 Aug 2026 02:18:48 -0700 (PDT) Date: Wed, 26 Aug 2026 09:18:22 +0000 In-Reply-To: <20260826-gmem-inplace-conversion-v11-0-0a15d8a799aa@google.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260826-gmem-inplace-conversion-v11-0-0a15d8a799aa@google.com> X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Developer-Signature: v=1; a=ed25519-sha256; t=1787735885; l=1693; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=xxgZV80P6tEBI0TS9iatKBLUXrCS72RFfbwoyow/L9Y=; b=I0SLEj0chvLQHB7QukPCMKxNVTQmEiLmipqoJJ+EGN6XfzLrsg82kHlLQjvE5ty/DdT4FbHrE xe7LXVIZZMOCZA0s06FUNYPGMQazgE0t9Oi6aKm/qrHRQUgS8sydK6J X-Mailer: b4 0.16.0 Message-ID: <20260826-gmem-inplace-conversion-v11-24-0a15d8a799aa@google.com> Subject: [PATCH v11 24/46] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs From: Ackerley Tng To: aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, david@kernel.org, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Fuad Tabba , Vlastimil Babka Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev, Ackerley Tng , Xiaoyao Li Content-Type: text/plain; charset="utf-8" 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 in-place conversion is enabled, i.e. when it's actually possible for a guest_memfd instance to contain shared memory. Signed-off-by: Sean Christopherson Reviewed-by: Fuad Tabba Reviewed-by: Xiaoyao Li Tested-by: Shivank Garg Reviewed-by: Binbin Wu Signed-off-by: Ackerley Tng --- arch/x86/kvm/x86.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 147b3e529cd26..45ef4156274ec 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10637,14 +10637,15 @@ 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 is supported if in-place conversion is enabled, or if + * the VM doesn't support private memory. If the VM has private memory + * and in-place conversion is disabled, then guest_memfd can _only_ be + * used for private memory. + */ + return gmem_in_place_conversion || !kvm_arch_has_private_mem(kvm); } #ifdef CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT -- 2.55.0.887.g758fc8c411-goog