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Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=satlexmb07.amd.com; pr=C Received: from satlexmb07.amd.com (165.204.84.17) by IA0PEPF0000003D.mail.protection.outlook.com (10.167.249.74) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.496.14 via Frontend Transport; Wed, 7 Oct 2026 13:43:46 +0000 Received: from localhost (10.180.168.240) by satlexmb07.amd.com (10.181.42.216) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.49; Wed, 7 Oct 2026 08:43:45 -0500 From: Michael Roth To: CC: , , , , , , , , , , Subject: [PATCH v3 09/19] accel/kvm: Handle guest_memfd flags internally when creating instances Date: Wed, 7 Oct 2026 08:41:33 -0500 Message-ID: <20261007134323.1606088-10-michael.roth@amd.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261007134323.1606088-1-michael.roth@amd.com> References: <20261007134323.1606088-1-michael.roth@amd.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: satlexmb08.amd.com (10.181.42.217) To satlexmb07.amd.com (10.181.42.216) X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: IA0PEPF0000003D:EE_|LV2PR12MB5800:EE_ X-MS-Office365-Filtering-Correlation-Id: a76f6379-9cde-4b70-bd93-08df247902f1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|23010399003|82310400026|1800799024|7416014|376014|36860700016|18002099003|22082099003|56012099006|6133799003|11063799006|10067099003; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: B2rKC0vguG9zGuViTo9RdkMRhi7F8mq4WRy/OT3J911JqGhvsbpIYNSU4Rr9pTVTA48eEoUsSVpbEzT7lTslUOL3sR3Nun459BQ+S8/Fi0znP4xqLrdzZAj2GNg21oakL3XPALs7XDPmjcMxq6VsW/TuY4xoOH4IoLnkZJbCveZg6/pHwcCIcLtWb8ZPGPPKqq2tI4RZXZ3y2RDEluIP/eFl6zSEUWFOhKmGwSHUd7LtNkWmviH53XBSvitMzvW2laUbd+GrK07QrTHz9gl5GakwL7/UTfc3ASPdXQX+6AVCfuNp2Q0fpZn7yZMqP23/FkiuCg126ErS9ZlI+nJODY3Fgy+O+cNAxcHvHaL7PSMf8GiKf8gtS7jPaQGbi0mVhqYetgiBH1Ldn8H+aRAKDUHNQ0gtZQD5f+KNTdx1acLTjM1IhBxMhKnrm4+xhkyJ X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Oct 2026 13:43:46.7464 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: a76f6379-9cde-4b70-bd93-08df247902f1 X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=3dd8961f-e488-4e60-8e11-a82d994e183d;Ip=[165.204.84.17];Helo=[satlexmb07.amd.com] X-MS-Exchange-CrossTenant-AuthSource: IA0PEPF0000003D.namprd03.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: LV2PR12MB5800 Current hostmem code (which is callable even outside of KVM) specifies guest_memfd flags directly, which requires pulling in kernel headers. Additionally, it will eventually require additional knowledge that is more suitable for KVM-aware code (e.g. whether or not to default to private memory for confidential VMs). Instead, push the determination for what flags are needed down into the KVM/guest_memfd code so they can be handled internally based on VM type/configuration and avoid further potential leakage of KVM-specific code to general code. Signed-off-by: Michael Roth --- accel/kvm/kvm-all.c | 26 ++++++++++++++++++++++++-- accel/stubs/kvm-stub.c | 2 +- backends/hostmem-memfd.c | 5 +---- include/system/kvm.h | 2 +- 4 files changed, 27 insertions(+), 8 deletions(-) diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c index 862539aed4..8cd1671ad5 100644 --- a/accel/kvm/kvm-all.c +++ b/accel/kvm/kvm-all.c @@ -4857,7 +4857,8 @@ void kvm_mark_guest_state_protected(void) kvm_state->guest_state_protected = true; } -int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp) +static int kvm_create_guest_memfd_flags(uint64_t size, uint64_t flags, + Error **errp) { int fd; struct kvm_create_guest_memfd guest_memfd = { @@ -4897,6 +4898,27 @@ int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp) return fd; } +int kvm_create_guest_memfd(uint64_t size, Error **errp) +{ + /* + * There isn't currently any use for non-mmap()'able gmem instances + * outside of kvm_create_guest_memfd_private(), so hardcode it here + * for general use. + * + * Additionally, *_INIT_SHARED is needed for non-confidential VMs, and + * confidential VMs will default to this as well to allow similar flows + * for initializing the VM's initial memory contents as with normal + * guests. In the future, the initial state may become a global policy + * decision based on the confidential VM configuration, in which case + * this would likely be the right place to decide whether or not to set + * the flag since it would likely be a globally-configured option. + */ + return kvm_create_guest_memfd_flags(size, + GUEST_MEMFD_FLAG_MMAP | + GUEST_MEMFD_FLAG_INIT_SHARED, + errp); +} + int kvm_create_guest_memfd_private(uint64_t size, Error **errp) { if (!(kvm_supported_memory_attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE)) { @@ -4904,5 +4926,5 @@ int kvm_create_guest_memfd_private(uint64_t size, Error **errp) return -1; } - return kvm_create_guest_memfd(size, 0, errp); + return kvm_create_guest_memfd_flags(size, 0, errp); } diff --git a/accel/stubs/kvm-stub.c b/accel/stubs/kvm-stub.c index 9fe58efe91..26003b01a3 100644 --- a/accel/stubs/kvm-stub.c +++ b/accel/stubs/kvm-stub.c @@ -139,7 +139,7 @@ bool kvm_hwpoisoned_mem(void) return false; } -int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp) +int kvm_create_guest_memfd(uint64_t size, Error **errp) { error_setg(errp, "KVM is not enabled"); return -ENOSYS; diff --git a/backends/hostmem-memfd.c b/backends/hostmem-memfd.c index c1ea6eefbd..d3b17232f0 100644 --- a/backends/hostmem-memfd.c +++ b/backends/hostmem-memfd.c @@ -70,10 +70,7 @@ memfd_backend_memory_alloc(HostMemoryBackend *backend, Error **errp) return false; } - fd = kvm_create_guest_memfd(backend->size, - GUEST_MEMFD_FLAG_MMAP | - GUEST_MEMFD_FLAG_INIT_SHARED, - errp); + fd = kvm_create_guest_memfd(backend->size, errp); } else { fd = qemu_memfd_create(TYPE_MEMORY_BACKEND_MEMFD, backend->size, m->hugetlb, m->hugetlbsize, m->seal ? diff --git a/include/system/kvm.h b/include/system/kvm.h index b1e43ddc93..2a1501bba6 100644 --- a/include/system/kvm.h +++ b/include/system/kvm.h @@ -547,7 +547,7 @@ void kvm_mark_guest_state_protected(void); */ bool kvm_hwpoisoned_mem(void); -int kvm_create_guest_memfd(uint64_t size, uint64_t flags, Error **errp); +int kvm_create_guest_memfd(uint64_t size, Error **errp); int kvm_create_guest_memfd_private(uint64_t size, Error **errp); int kvm_set_memory_attributes_private(hwaddr start, uint64_t size); -- 2.43.0