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Peter Anvin" , "Peter Zijlstra (Intel)" , Borislav Petkov , Dave Hansen , Ingo Molnar , "Mathieu Desnoyers" , Paolo Bonzini , Sairaj Kodilkar , "Sean Christopherson" , Thomas Gleixner , "Uros Bizjak" , , , CC: , Subject: [PATCH v2 0/2] Add support for cmpxchg16b emulation Date: Mon, 6 Jul 2026 12:00:33 +0530 Message-ID: <20260706063035.1139-1-sarunkod@amd.com> X-Mailer: git-send-email 2.34.1 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: SJ1PEPF00001CE2:EE_|CYXPR12MB9441:EE_ X-MS-Office365-Filtering-Correlation-Id: 21a0514e-9f38-4293-5ffb-08dedb284769 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|23010399003|1800799024|82310400026|376014|36860700016|921020|3023799007|13003099007|18002099003|56012099006|11063799006; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:165.204.84.17;CTRY:US;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:satlexmb07.amd.com;PTR:InfoDomainNonexistent;CAT:NONE;SFS:(13230040)(7416014)(23010399003)(1800799024)(82310400026)(376014)(36860700016)(921020)(3023799007)(13003099007)(18002099003)(56012099006)(11063799006);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: 0pLO+tmCEZLCG0fOCAYA9v8JWo46Ceql0hrrCKbVQBClryF42DkiP8BhEg6MBn6yjZHDaNF/OxLRCPh9ID0ACeypFeOC3Xc5Z+GqOMxoz2iy+ymi+YYxR3HUKIdSh33D12p2HtLnJnUlmBn7tv/FdpUJZlzczs3N5JCiMmYLbTZkv/8ps/9SG9tFlCnncu8dB+Ygwz/rFgcAOOHEwp/NNULEkyxpIfNm+ueGnZ4EEGeabZtMleFz51B1gjN4hErJzG+uDmzZQ/d7BCHaQse2sTePkb/TkMJpT9vd+aKYOpODI7h105DtgvZv/08V1zCn4eTcSAeBnRaMrjeZlb8fjjuCKHTQmUpcmb2jskyWL94d8444gjXb1tSnHjxC8139jQlgm434FsRbtpCCkAdBBUwpnEBfMP8r3ABsJEOkF4Iyece9EdT38WEjo/wN/wO5 X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jul 2026 06:31:57.5093 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 21a0514e-9f38-4293-5ffb-08dedb284769 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: SJ1PEPF00001CE2.namprd05.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: CYXPR12MB9441 This series adds 128-bit compare-exchange support needed for KVM to emulate guest cmpxchg16b instructions. The AMD IOMMU driver updates 256-bit device table entries with two 128-bit cmpxchg operations. For hardware-accelerated vIOMMU, QEMU traps those DTE accesses to install nested page tables [1]. KVM must emulate guest cmpxchg16b on the trapped MMIO regions; without that, DTE access emulation fails. Patch 1: extends the x86 user CMPXCHG helpers with __try_cmpxchg128_user_asm() (cmpxchg16b on x86-64), wired into unsafe_try_cmpxchg_user(). Patch 2: extends KVM CMPXCHG8B emulation to 16-byte operands (REX.W=1) and uses the new helper for atomic 16-byte compare-exchange on guest RAM via emulator_cmpxchg_emulated(). You can find the KUT to test this series at [2]. [1] https://github.com/AMDESE/qemu-iommu/blob/wip/for_iommufd_hw_queue-v8_amd_viommu_20260106/hw/i386/amd_viommu.c#L517 [2] https://lore.kernel.org/kvm/20260706062153.346-1-sarunkod@amd.com/T/#u --- Base: 8cd9520d35a6c38db6567e97dd93b1f11f185dc6 --- Sairaj Kodilkar (2): x86/uaccess: Extend CMPXCHG user helpers to 128-bit operands KVM: x86: Add support for cmpxchg16b emulation arch/x86/include/asm/uaccess.h | 56 +++++++++++++++++++++++++++++++++- arch/x86/kvm/emulate.c | 50 ++++++++++++++++++++---------- arch/x86/kvm/kvm_emulate.h | 6 ++++ arch/x86/kvm/x86.c | 7 ++++- 4 files changed, 101 insertions(+), 18 deletions(-) -- 2.34.1