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envelope-from=jgg@nvidia.com; helo=NAM11-CO1-obe.outbound.protection.outlook.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@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-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Tue, May 16, 2023 at 02:35:21PM +0000, Shameerali Kolothum Thodi wrote: > Ok. Got it. So it depends on what SMMU does for that mapping and is not > related to migration per se and has the potential to crash the system if > SMMU go ahead with that memory access. Isn't it a more generic problem > then when we have multiple devices attached to the VM? It is, and I am hoping to solve it when I get P2P support into iommufd > I need to check if there is anything in SMMU spec that forbids this > access. There isn't, it is up to the integration how it handles 'hairpin' traffic. A good implementation will work correctly as Intel and other CPUs do. A very bad implementation will crash. Medium is to return error tlps. Jason