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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?uebmAnfpF6jwrM1VX1ztD7t7d9KWoYY07QC1HFvbG7AL795mU5NCnleno+VI?= =?us-ascii?Q?YkRP+txBuQW8b+1CZtNS+QWhK+1DPsClBLeFOQ/83ZzUTtFD9nQbdu9P+u1e?= =?us-ascii?Q?ggRdtVq/o0w5u/iCOmVSMyeB267EyTrzUKvSA+3geoK/Lab6Xccdqferi9Hd?= =?us-ascii?Q?Wp5d2RQNXrLcxw8qqfG9/dfxKsIlxpkmM/D3gpYaKlRdcXCEuNEcs66VN9pO?= =?us-ascii?Q?HHy4fAywB7QyQh6Yph5b9HttCEGkRH2ucxKjQiLWAnRNeRhvPhFOUMBNPPWI?= =?us-ascii?Q?EOUK3PRIQPtr1JKvDGZtf0q5wqW2Hl57MmOtbdgIkQ6mMXUiZgRlM8Yo3+vi?= =?us-ascii?Q?cWPtye0K8CZOEP9/iP3yuCYKuARBohjTb58QT7WFuYPVkcvucAea3zqJiehY?= =?us-ascii?Q?oSM58EPR83dRi+1DBS0NcS/gJ7LXC/sA2MmpMyJ0DaJLeUf1qPkT6SevgcdP?= =?us-ascii?Q?tz9i3R1ThXgIhjyxVGKc/Je4XjcogZt0b3XId8qflvtpqBScu3N3OrfuaZYz?= =?us-ascii?Q?NpXrtBgpvUSwUFN1iyQ/FW6xPU3Sfz/0my5Nr0Z+GYftr0MZ5/4d3Wpqz7AC?= =?us-ascii?Q?Za5AGgBJNU0I/mGPZUWOKhjG/kIB/r3WWEvglMGSREfk7L40oZLBx6vPDLUB?= =?us-ascii?Q?LP4khoAfm+/3oOn+HauiF/F7x6klOIWJv9d3fiLUZZQV4oMdYRCzzDHszz51?= =?us-ascii?Q?xaeJpt10jHgyrP9Y6s4UT7N9faRcxmNMO4hOQF8ep02efDBplvylQQ4MNGxd?= =?us-ascii?Q?+fSqAazsPglyhNYvJjNR6v5t7EsX/jvbW2LFQRYE2f+N0L0sbuHb6BI5lsqe?= =?us-ascii?Q?Yh2VDQKypqbX0QnPVdt8j7/PX9HkoQnZEaz34VqoJSjutQGA/N1zvOH753wf?= =?us-ascii?Q?Sp4hbw0YlfXOvzf/5IaBBt0/TvQdxTycJA3Dbbv9RYS5ACQ3Iyh83ugQQ/8S?= =?us-ascii?Q?Ram4CzNtpu1BwotJs+ztkq5so300uo/APRm2v6ox19qAGOGXHln7P7SdH8T6?= =?us-ascii?Q?cndUbSEqXCC3LlEZaFfQUGvxxgrCMpi2KEUkB8VinaXAw99qvMLzWBJqcWRz?= =?us-ascii?Q?CiCNETQolGubnwMAo7frKdPyJ81jJ13JI2ivVWW6wReGyrMDdmaT4pX8HpsA?= =?us-ascii?Q?/fHbSiHVLPeT+4RnW49uQKDuGPiDPnvw1l0FW/vr0ymNzsS8/dExR09Zzmwq?= =?us-ascii?Q?jDeFrek4U24Ywq74x4wqize0Ah25wLS+xPRMqfNl7ZuswxJRsuqP8gaOl/90?= =?us-ascii?Q?VRSKvQA1395oDtnc4OV8oIxJXrM7UOK+vHAwnkJOQ7ohhr9rw0cIFCwtPWA9?= =?us-ascii?Q?Df7ZsLoxjRoGIh/VNYVzkasHr3vLP2rmrsgJxEviuTMUxAGR0xmtc4OvuBnE?= =?us-ascii?Q?SfwfUQ1Oe8muH+M/5jgwbmmTUBR20IuCC3u+Qlbeow7r1fz+lqzZ4Qi5CHoD?= =?us-ascii?Q?Y5N91fUKunrqXSiA49YXaSFhIyAF+r9mJDvg2AjwhvJhzwCMVuSrSuLVzeHm?= =?us-ascii?Q?keHi+TpZjOmOGllaZ11ys9g4DHZVr7PGkDaoOcaRIMxOTq4OBktMAouBDAav?= =?us-ascii?Q?OPw1AH1MicIXGQje/SNPTq6LQwm8aW+cgJDE9qhj?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 50f74521-38e6-4fe5-9f70-08dd3bb3c670 X-MS-Exchange-CrossTenant-AuthSource: CH3PR12MB8659.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Jan 2025 13:42:27.2442 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 8Ci3ihd5n9pBte2N/abOaAWRcRvaeVCuvW44mEOxl4y4yr7RrsK2FQqao1U4cMFW X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN7PR12MB7252 On Wed, Jan 22, 2025 at 11:54:52AM -0800, Nicolin Chen wrote: > ARM seems to also have an interesting event merging feature: > STE.MEV, bit [83] > Merge Events arising from terminated transactions from this stream. > 0b0 Do not merge similar fault records > 0b1 Permit similar fault records to be merged > The SMMU might be able to reduce the usage of the Event queue by > coalescing fault records that share the same page granule of address, > access type and SubstreamID. > Setting MEV == 1 does not guarantee that faults will be coalesced. > Setting MEV == 0 causes a physical SMMU to prevent coalescing of > fault records, however, a hypervisor might not honour this setting > if it deems a guest to be too verbose. > Note: Software must expect, and be able to deal with, coalesced fault > records even when MEV == 0. > > Yet, the driver doesn't seem to care setting it at this moment. Yeah, we will eventually need to implement whatever DOS mitigations are included in the IOMMU architectures.. I think DOS testing the event architecture should be part of the testing/qualification. It should be quite easy to make a DOS spammer using VFIO in userspace in the VM to test it with the mlx5 vfio driver.. (though you need VFIO to work in a VM which RMR will prevent, but that can be hacked around I guess) Jason