From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EFC9739F188; Tue, 28 Apr 2026 23:25:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777418719; cv=none; b=a/AC8btwNrLq1xLdVVAD/4UfrP//xSX2ZgRSyS/gMUn6SqdCihDHkH60VNvbNRWWT3EL8N8g1ktCe0tIUSTn4LPBnVcNQOLEAob5JxHqWqMHjmCIweJhEUvrHrJIc4d1ILF5QybkDBX1/064eY1muR35+cPr4ApE1pSTplRStMw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777418719; c=relaxed/simple; bh=UjB3Q8xP2+/jLCiODH+4GnaWPfVWe36CvWf3Dh0lyNw=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=t0otwK7ohEU1g22HVMM1AFWDTB1CU/p6a37Vf8bVFCbvTtnew6i16Es6E248FAr8G3Bu4qnXw6wkk67Yy+znqN6RDWPRW0cr6hVwKzgR+cHimz7T2/xPWOz0epRmuwKcuCi8RbeoB8p4y9zOV4MY5p0aAfGPLJLm6iRLbJzpNXc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=tk8v8nB7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="tk8v8nB7" Received: by smtp.kernel.org (Postfix) with ESMTPS id CF6DFC4AF19; Tue, 28 Apr 2026 23:25:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777418718; bh=UjB3Q8xP2+/jLCiODH+4GnaWPfVWe36CvWf3Dh0lyNw=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=tk8v8nB7bwg2HgNUKy/3dSbh1sX2By5WJlLidJ1Av30V2f3k8yXSOmd3d+RIsUiTG FKfPonFTqIELdBlrt1T2Ywoi5P6ZM4bQIS8EFRNrUskt+Wspz90GIXlWQhWORJshWf H7K7bd4oD2xfuKY2gyqJZeb89PAcC87zJvPQz97dJjle3Q5+ztTFAk3SvnakeKdPE7 axiMB8p1x8M+XFyPbHFq9CBisWa9EuoFmU2VCWYyK2961IoaKOrxGnTvCveRQ2u4s0 SB+exL1U3B6OIz1E8XCK3DHJaiWTF7AdW3OtQI9znXEO7A03DDQnaFocSs8sFDcrwY oIiepIJK9AfVQ== 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 BD332FF8875; Tue, 28 Apr 2026 23:25:18 +0000 (UTC) From: Ackerley Tng via B4 Relay Date: Tue, 28 Apr 2026 16:25:15 -0700 Subject: [PATCH RFC v5 20/53] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260428-gmem-inplace-conversion-v5-20-d8608ccfca22@google.com> References: <20260428-gmem-inplace-conversion-v5-0-d8608ccfca22@google.com> In-Reply-To: <20260428-gmem-inplace-conversion-v5-0-d8608ccfca22@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, 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=1777418714; l=1390; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=9LP/svD9TvgxKqvednNMupCSsWJ+AFS+3tUCHtCnRqA=; b=7TverXUJlngRxhJ4vEWJkucYIO7XShyfSISUb/HZPT3irzIwFpodwZIaXKo0xt09LhSOu99cl vzzDW2Ybw7TASLiyA7ny4f0JXMSI7+HJSNDTw51rwwdQnOzO+yzu59J 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 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 -- 2.54.0.545.g6539524ca2-goog