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Thu, 7 May 2026 20:22:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778185371; bh=kuvf1QytKNmWpbqV5ZSDGpv2N4AjU4Sqs1rvh9b2g7c=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=BkIORK8qYTAnm2VU49jRDbUko2CyK3uAgcNeRl3TBK3CJItP1Wal7F3Om8ev1LPtu LFnDs9CXAMhNpzNf+Cb+MZvOwaiw9HaxX5drka5j2mxB/++qR0qFqZvWIvt9kU52ms D3Xqi9gun6bs2xpaP7BiWKyyLoNytTf9LNvO0GnA6CMITzxH7OFm+ik8VSqDXMs5OP qChzXN8wh6Q26uyagCLQj5kLfC3bNparYD+OZ/ZQIijFoexWoPMzk7KPPQfxnGPOgV ZIjtlHlZ4uyqi6/lacJQaLNv27aDQpPnE+jsx9/2OZ0+KErzrmfPYj0AkGC8VTpLBw TfScj/eu/6JDg== Received: from aws-us-west-2-korg-lkml-1.web.codeaurora.org (localhost.localdomain [127.0.0.1]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9092CD343F; Thu, 7 May 2026 20:22:50 +0000 (UTC) From: Ackerley Tng via B4 Relay Date: Thu, 07 May 2026 13:22:39 -0700 Subject: [PATCH v6 20/43] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260507-gmem-inplace-conversion-v6-20-91ab5a8b19a4@google.com> References: <20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com> In-Reply-To: <20260507-gmem-inplace-conversion-v6-0-91ab5a8b19a4@google.com> 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, ira.weiny@intel.com, 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, tabba@google.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 , Baoquan He , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Jason Gunthorpe , 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 X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=ed25519-sha256; t=1778185365; l=1390; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=4th485qJtPy9D3mUoIORJhfE2BOpFshMa4hW0RxvNaU=; b=cfh6kq6WIGvAJNv/sMpeHDw0eVPS4Kih4J+DT/ModMbPkUjKWNfXuj744TOQCrKVG9CIv9CXu hv921YxLxRMCed3DoJV+8+z5iUMWDyJVfeMN7gBq7oFrmBi0MmYhNO2 X-Developer-Key: i=ackerleytng@google.com; a=ed25519; pk=sAZDYXdm6Iz8FHitpHeFlCMXwabodTm7p8/3/8xUxuU= X-Endpoint-Received: by B4 Relay for ackerleytng@google.com/20260225 with auth_id=649 X-Original-From: Ackerley Tng Reply-To: ackerleytng@google.com X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 208144000D X-Stat-Signature: 15moxxfkwikswc5uz41bwjd675hqpig8 X-Rspam-User: X-HE-Tag: 1778185377-581801 X-HE-Meta: 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 hBGiURY8 N+xux7fmeN6zDJpHFWydItyM3azLMePrIqCYyW3mjwIJozbmIQw7VxgS2jw8sXcnzuztPvyJAZfDFz+8szs6Vw91AegNln4pIPdeB40kLEv40u+L0tPYLf184RQ+kju5jlL62bK29T2HGvvE+6m7qSnzRKxVj1UzY9o4LIR7iyPnjdU+0GRFWigBP5pgdpgcGkdQI+HM6x7SqQGqipbTjhh9OsXWe2NE+xnE/eaCqJDgLiPWztE5VivvHqZ7laR1Wmu9xqzD/AbGGHs6I25IRZLHPa77txce03IRhYGZi6Fk33u/EYb5PK9xII7fQKcc0SouG9YR6LH7HTKXk16x7serFjjprKX9JCB43iFP1MCTyI5zAcSYlxBSzT8D6mbCuVjjADQSbNWfFtl9xw7iqU2+al/zuuNM/7kSCcLGD/FIWw9WEAiQmwzbTuc6DNiEH/EVpaXERiGBTDhjEQp7r5p7rXg== 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 Signed-off-by: Ackerley Tng --- 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 1560de1e95be0..6609957ecfea3 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -14172,14 +14172,13 @@ 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 -- 2.54.0.563.g4f69b47b94-goog