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 AFDAA3A4F23; Tue, 28 Apr 2026 23:25:19 +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=jVO643NML90Yt1d7qRaS076bY6NuLRYjYFR/rVGSC8YyGiKJ4hSIfkPIHDJ5X/t0l9G3k9Vk6dj+OP04AIRfcInHqq8LCwaCzCH/9Y1GPYdmbJYVcqEZySTdpBmJlzexDVtm3wKsg8sPQU8vIxF2xyrOs7pC0eAVIx0+QF5Z2pI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777418719; c=relaxed/simple; bh=8ldZ9tHAeXetrK8aWEmsZfkrv8T0wMkcO8Q1/+uxlWI=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=lti/U2xlhkKnevq7fqKdDG5tg9ZAGAZL4lHTI98OZguQnUK//qhqGXIDxszq2RRKIetPWmKmasSypPcYv4MZUdTyvi0FrOcqpmNiR5v1TYAqnxCoje+eWYWKHu2ug7/VaS1apq4zxIlYQ2c+sDBieJpPmdtyHOVazpwoR5pQQns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KPo1ak4h; 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="KPo1ak4h" Received: by smtp.kernel.org (Postfix) with ESMTPS id 93FFFC2BCB7; Tue, 28 Apr 2026 23:25:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777418719; bh=8ldZ9tHAeXetrK8aWEmsZfkrv8T0wMkcO8Q1/+uxlWI=; h=From:Date:Subject:References:In-Reply-To:To:Cc:Reply-To:From; b=KPo1ak4h7ief2ISZWZW/EZ/7mUK0FEIdHn2SODaZCs0Xf9ufV8ZFGVD+Zvn1XPy16 hOPfyNzOV+QHcobBqaiFHqyiR564LH6VCqekgHYYkg/Y8lwpVVCgKYBlgKuuctko5o enSa0z2IGSPOyRO49DfClhcVZS8kELk+tSkcoG5HsX+wHT9yMv64B6Isrxj/DOkR3d 64p1juXX/MayYcil/tbYNM8OzvEoLcNYa/EoZUr012aUdWyzvQNAQbsxNL+wdycRsN MF6X1JVo+QubUlUkjEa6BJGfJx/+cOZhRxthZAaXtQuEm235OEBXyBl1KbexW7FOGh 8X7sSXG5wpFKw== 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 88EE9FF8877; Tue, 28 Apr 2026 23:25:19 +0000 (UTC) From: Ackerley Tng via B4 Relay Date: Tue, 28 Apr 2026 16:25:23 -0700 Subject: [PATCH RFC v5 28/53] KVM: Add CAP to enumerate supported SET_MEMORY_ATTRIBUTES2 flags 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-v5-28-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=5528; i=ackerleytng@google.com; s=20260225; h=from:subject:message-id; bh=pIqYKdyBIT9N1Rsog/1YD0EZWPUQYi37ZuQ2ZuzAyaY=; b=LQBZ48AGkz7+oQLurDh/BMdAf+VaqtbjZWVqTJOoJUGv/ubksh354Cn4r3Ib2Hs6R4f/Dz53w n3OEKv307fhDKS75Bmp15XQZ4T1xi6Ti7nszk4NxAk+S39eJn3ZXztw 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: Ackerley Tng Add CAP to enumerate supported SET_MEMORY_ATTRIBUTES2 flags, so userspace can find out which flags are supported when sending the KVM_SET_MEMORY_ATTRIBUTES2 ioctl to a guest_memfd. Add a parameter for_cap to support enumeration of supported flags irrespective of attribute being set. These flags are only supported by guest_memfd, hence, if vm_memory_attributes is enabled, return 0 - no flags are supported when KVM_SET_MEMORY_ATTRIBUTES2 is sent to a VM fd. Signed-off-by: Ackerley Tng --- Documentation/virt/kvm/api.rst | 3 +++ arch/x86/kvm/x86.c | 5 +++-- include/linux/kvm_host.h | 11 ++++++++++- include/uapi/linux/kvm.h | 1 + virt/kvm/guest_memfd.c | 6 ++++-- virt/kvm/kvm_main.c | 5 +++++ 6 files changed, 26 insertions(+), 5 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index aaa4a82f0b75d..38938243c2dfd 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6685,6 +6685,9 @@ guarantees are made on offset ranges that do not have memory allocated and range [0x0000, 0x3000) was set to shared, the content mode would apply to only to offset ranges [0x0000, 0x1000) and [0x2000, 0x3000). +The supported content modes can be queried using +``KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS``. + See also: :ref: `KVM_SET_MEMORY_ATTRIBUTES`. .. _kvm_run: diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 296ed3b8ace6c..92709735613d5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -14195,7 +14195,8 @@ void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end) } #endif -u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private) +u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private, + bool for_cap) { if (!kvm) { return KVM_SET_MEMORY_ATTRIBUTES2_ZERO | @@ -14227,7 +14228,7 @@ u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private) * shared, memory contents for pages that had already * been faulted could be zeroed. */ - if (to_private && !kvm->arch.pre_fault_allowed) + if (for_cap || (to_private && !kvm->arch.pre_fault_allowed)) supported |= KVM_SET_MEMORY_ATTRIBUTES2_PRESERVE; return supported; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 458bad0083c37..13d126dde32f1 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -742,7 +742,8 @@ static inline u64 kvm_gmem_get_supported_flags(struct kvm *kvm) return flags; } -u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private); +u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private, + bool for_cap); int kvm_gmem_apply_content_mode_zero(struct inode *inode, pgoff_t start, pgoff_t end); int kvm_arch_gmem_apply_content_mode_zero(struct kvm *kvm, struct inode *inode, @@ -2551,6 +2552,14 @@ static inline u64 kvm_supported_mem_attributes(struct kvm *kvm) return 0; } +static inline u64 kvm_supported_set_mem_attributes2_flags(struct kvm *kvm) +{ + if (!IS_ENABLED(CONFIG_KVM_GUEST_MEMFD)) + return 0; + + return kvm_arch_gmem_supported_content_modes(kvm, false, true); +} + typedef unsigned long (kvm_get_memory_attributes_t)(struct kvm *kvm, gfn_t gfn); DECLARE_STATIC_CALL(__kvm_get_memory_attributes, kvm_get_memory_attributes_t); diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index c7cc6c22c2023..c0d465a5577da 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -997,6 +997,7 @@ struct kvm_enable_cap { #define KVM_CAP_S390_KEYOP 247 #define KVM_CAP_S390_VSIE_ESAMODE 248 #define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 249 +#define KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS 250 struct kvm_irq_routing_irqchip { __u32 irqchip; diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 5c1db67e6fd35..071bf636ba5c0 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -693,7 +693,8 @@ static void kvm_gmem_invalidate(struct inode *inode, pgoff_t start, pgoff_t end) static void kvm_gmem_invalidate(struct inode *inode, pgoff_t start, pgoff_t end) {} #endif -u64 __weak kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private) +u64 __weak kvm_arch_gmem_supported_content_modes(struct kvm *kvm, + bool to_private, bool for_cap) { /* Architectures must override with supported modes. */ return 0; @@ -709,7 +710,8 @@ static bool kvm_gmem_content_mode_is_supported(struct kvm *kvm, if (content_mode == KVM_SET_MEMORY_ATTRIBUTES2_ZERO && to_private) return false; - return kvm_arch_gmem_supported_content_modes(kvm, to_private) & content_mode; + return kvm_arch_gmem_supported_content_modes(kvm, to_private, false) & + content_mode; } int kvm_gmem_apply_content_mode_zero(struct inode *inode, pgoff_t start, diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 3bf212fd99193..9fa6ecebab939 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4979,6 +4979,11 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) return 0; return kvm_supported_mem_attributes(kvm); + case KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS: + if (vm_memory_attributes) + return 0; + + return kvm_supported_set_mem_attributes2_flags(kvm); #endif default: break; -- 2.54.0.545.g6539524ca2-goog