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CTRY:US; LANG:en; SCL:1; SRV:; IPV:NLI; SFV:NSPM; H:mail.nvidia.com; PTR:dc7edge2.nvidia.com; CAT:NONE; SFS:(13230040)(7416014)(376014)(1800799024)(82310400026)(36860700013); DIR:OUT; SFP:1101; X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 Nov 2025 19:34:02.2144 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: eefed976-056b-4046-28e9-08de1ca2465c X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=43083d15-7273-40c1-b7db-39efd9ccc17a; Ip=[216.228.118.233]; Helo=[mail.nvidia.com] X-MS-Exchange-CrossTenant-AuthSource: BN3PEPF0000B374.namprd21.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR12MB6902 Received-SPF: permerror client-ip=2a01:111:f403:c111::5; envelope-from=nicolinc@nvidia.com; helo=DM1PR04CU001.outbound.protection.outlook.com X-Spam_score_int: -15 X-Spam_score: -1.6 X-Spam_bar: - X-Spam_report: (-1.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.517, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FORGED_SPF_HELO=1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-0.001, SPF_NONE=0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-arm@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org Sender: qemu-arm-bounces+qemu-arm=archiver.kernel.org@nongnu.org On Wed, Nov 05, 2025 at 02:58:16PM -0400, Jason Gunthorpe wrote: > On Wed, Nov 05, 2025 at 10:33:08AM -0800, Nicolin Chen wrote: > > On Wed, Nov 05, 2025 at 02:10:49PM -0400, Jason Gunthorpe wrote: > > > On Wed, Nov 05, 2025 at 06:25:05PM +0100, Eric Auger wrote: > > > > if the guest doorbell address is wrong because not properly translated, > > > > vgic_msi_to_its() will fail to identify the ITS to inject the MSI in. > > > > See kernel kvm/vgic/vgic-its.c vgic_msi_to_its and > > > > vgic_its_inject_msi > > > > > > Which has been exactly my point to Nicolin. There is no way to > > > "properly translate" the vMSI address in a HW accelerated SMMU > > > emulation. > > > > Hmm, I still can't connect the dots here. QEMU knows where the > > guest CD table is to get the stage-1 translation table to walk > > through. We could choose to not let it walk through. Yet, why? > > You cannot walk any tables in guest memory without fully trapping all > invalidation on all command queues. Like real HW qemu needs to fence > its walks with any concurrent invalidate & sync to ensure it doesn't > walk into a UAF situation. > > Since we can't trap or mediate vCMDQ the walking simply cannot be > done. > > Thus, the general principle of the HW accelerated vSMMU is that it > NEVER walks any of these guest tables for any reason. > > Thus, we cannot do anything with vMSI address beyond program it > directly into a real PCI device so it undergoes real HW translation. It's clear to me now. Thanks for the elaboration! Nicolin