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Received: from MN2PR12MB4192.namprd12.prod.outlook.com (2603:10b6:208:1d5::15) by DM4PR12MB5343.namprd12.prod.outlook.com (2603:10b6:5:389::17) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5314.13; Wed, 8 Jun 2022 11:17:26 +0000 Received: from MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::2484:51da:d56f:f1a5]) by MN2PR12MB4192.namprd12.prod.outlook.com ([fe80::2484:51da:d56f:f1a5%9]) with mapi id 15.20.5314.019; Wed, 8 Jun 2022 11:17:26 +0000 Date: Wed, 8 Jun 2022 08:17:24 -0300 From: Jason Gunthorpe To: "Tian, Kevin" Cc: Nicolin Chen , "joro@8bytes.org" , "will@kernel.org" , "marcan@marcan.st" , "sven@svenpeter.dev" , "robin.murphy@arm.com" , "robdclark@gmail.com" , "m.szyprowski@samsung.com" , "krzysztof.kozlowski@linaro.org" , "baolu.lu@linux.intel.com" , "agross@kernel.org" , "bjorn.andersson@linaro.org" , "matthias.bgg@gmail.com" , "heiko@sntech.de" , "orsonzhai@gmail.com" , "baolin.wang7@gmail.com" , "zhang.lyra@gmail.com" , "wens@csie.org" , "jernej.skrabec@gmail.com" , "samuel@sholland.org" , "jean-philippe@linaro.org" , "alex.williamson@redhat.com" , "virtualization@lists.linux-foundation.org" , "thierry.reding@gmail.com" , "alim.akhtar@samsung.com" , "alyssa@rosenzweig.io" , "linux-s390@vger.kernel.org" , "linux-samsung-soc@vger.kernel.org" , "kvm@vger.kernel.org" , "jonathanh@nvidia.com" , "linux-rockchip@lists.infradead.org" , "gerald.schaefer@linux.ibm.com" , "linux-sunxi@lists.linux.dev" , "linux-arm-msm@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , "linux-tegra@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , "cohuck@redhat.com" , "linux-kernel@vger.kernel.org" , "iommu@lists.linux-foundation.org" , "dwmw2@infradead.org" Subject: Re: [PATCH 3/5] vfio/iommu_type1: Prefer to reuse domains vs match enforced cache coherency Message-ID: <20220608111724.GL1343366@nvidia.com> References: <20220606061927.26049-1-nicolinc@nvidia.com> <20220606061927.26049-4-nicolinc@nvidia.com> Content-Type: text/plain; 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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?ZuxJJbH8qjGIDaAh3SXYcmnbQ48YErF4SCikA3b1V3JaUcRYWCR9Sn0Db+5w?= =?us-ascii?Q?VVsZMMHLjVVw/dT0yRZQpvkoDr4v5k+UfKuL+goXQF5HsRmzsx+rUeRVciuO?= =?us-ascii?Q?ApUOj44GgQvCoa2InUVqJ4VBWDgPMEn4qWoB0zx6fsw3sb9Y7KCGhg45pQIi?= =?us-ascii?Q?Zon8rxAGg2vXNQ+YN3hJRyolw1lxmIVXp5MJtpajlEtEAcHwioQ8tw7dh5K+?= =?us-ascii?Q?9vN7dhuMjve4o9j4wrBT5/9afAerVMGspV/qbhGcRjK7KFUeQoehpwTHEyL3?= =?us-ascii?Q?nYYyxs8HDiDlSxFtI0ziNU5M12sEN5IHKvQHmyMh9/7eTRQg0/3/ZI+v6EQC?= =?us-ascii?Q?mbhdK7qbOrBPZWvOzfniUotHvYpI2albWCRhBQCIYstGu5VvIS8fBjaS3Ttu?= =?us-ascii?Q?6MAKqQyQ6UBOrDVlzINFCmVV228vpGsu8TQ5lg7Y0o19AJAc1NkvmFObHOQ0?= =?us-ascii?Q?OaQDIPqTrl5fFtV2iRMSo4ceBXGGxOtctuTrhfO2QnPJj0m1t05JJTb2G/KC?= =?us-ascii?Q?/WHb3IWSR+N3FrrqSxwYAZcYAlU6FeN+cIlXBzD4gs2tTCmFaQ3hmodBKgDl?= =?us-ascii?Q?L3Qbc2s5C6TBppaD69bg4VI/ht+rDDnze0ATW+xulsgx+huqjOU7KwztF2kB?= =?us-ascii?Q?fZH5K+iuS43f2gsQ2cekA2UdFmvFZyLHn6uCxDroodhLfehwYurAR6BQXQW6?= =?us-ascii?Q?dQwBYDClyVJmcUa47y9uWVY9lCpT0qa+Hx91M6jJYuW+U6GY7qaUVnxh4mz1?= =?us-ascii?Q?YMT9fly+eSA4lG6KN/iAWfSLMXyNEvDo6AYXYMQV6hb9bPNbgeaVCpc+wOUi?= =?us-ascii?Q?fkOs2CHd0NKUIl3jNn7dobCasoCXw3W9yB3uG4JqW2kMorqqGP95+yxP3N/q?= =?us-ascii?Q?QTL8URMR8KHC8aoiPmVLU9TTuRFOffbw2NcjVQcvc0l4moGS+Un4i2BE/zAh?= =?us-ascii?Q?BOlFoLeKFe8L9m00Px5jlBPFdBJJGsLmMel7xMO+lz2V8jG7S/XK1zI1ZspF?= =?us-ascii?Q?PBennkNHEuzruBnlFhI8B2uOqogw5mlCLxxUgl2W8E9PZPOvjpZRQLUN8wb0?= =?us-ascii?Q?SymmRZW0N+gQH1pEa4/5VbCw00K8sTqp5xX5d/h6RxG6U8so3pXc3hFgc1dF?= =?us-ascii?Q?iuiNsu6IzJaRKtNF2nznl5J0w8bFSV6aIlz+98kNz8835uWnKgodkgcGKE+M?= =?us-ascii?Q?F/tCvQwH4iGGLYbeKBhpQWFh5dsssrwT1fV7VluQWi4VRoHarlU0D4Q9P2wa?= =?us-ascii?Q?+QLNlHtfl/btEkD78B83tGt9keL/FyUgUu5KgjS06WvdG8T+ravcgyyabrsP?= =?us-ascii?Q?nA7A8kUhp5n0Rfc4CGlJdlk6d/0eEmytSS8gWxJZaDKmxICPfU8IxIWPsza4?= =?us-ascii?Q?rx7pSxxY8HzTbfrcMreK6qeJJ36uMqcgU0ltblyMFwucHgec9PzO7jmYHOyv?= =?us-ascii?Q?6lwozP2oVdziNIEpwXfYA9s0Earq2mfB1WY+iZHjvvhHLmCLXcv5dfRtmfAm?= =?us-ascii?Q?GlG71sQouvV02fTDHncm4iyLuu8lBMaHcoaC+jHZStFiw9A6McRabHNERPAk?= =?us-ascii?Q?uTaBHoEnP78LVtptltLmQH1vei7K5GVQAErhawkyaUE54GvrGIeLVsLYncb1?= =?us-ascii?Q?q5gt8lY2xnHeaRLkZqhXUaawpICAM9Qzs40wNDCaK3Sgig9NGu5Mu/llotKP?= =?us-ascii?Q?BoOGhJmReHMuHKEXwWNJUjvizem2Ah7RXpZGqYHsMKT2Ws8KnKNo0a+7qQl2?= =?us-ascii?Q?NI8ZF7G2aw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7e109dbf-2d78-4e90-7279-08da494077d9 X-MS-Exchange-CrossTenant-AuthSource: MN2PR12MB4192.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 08 Jun 2022 11:17:26.5851 (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: NlzeZFRt8LJ1fNvLhsuAFFE01oM4KB5zTUX++2oN79OXPBUrX0li9IRGiFytH7Ir X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB5343 On Wed, Jun 08, 2022 at 08:28:03AM +0000, Tian, Kevin wrote: > > From: Nicolin Chen > > Sent: Monday, June 6, 2022 2:19 PM > > > > From: Jason Gunthorpe > > > > The KVM mechanism for controlling wbinvd is only triggered during > > kvm_vfio_group_add(), meaning it is a one-shot test done once the devices > > are setup. > > It's not one-shot. kvm_vfio_update_coherency() is called in both > group_add() and group_del(). Then the coherency property is > checked dynamically in wbinvd emulation: >From the perspective of managing the domains that is still one-shot. It doesn't get updated when individual devices are added/removed to domains. > given that I'm fine with the change in this patch. Even more probably > we really want an explicit one-shot model so KVM can lock down > the property once it starts to consume it then further adding a new > group which would change the coherency is explicitly rejected and > removing an existing group leaves it intact. Why? Once wbinvd is enabled it is compatible with all domain configurations, so just leave it on and ignore everything at that point. Jason