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DIR:OUT; SFP:1102; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?iso-8859-1?Q?Ge5vDMdZs0GAhjGxk81bBslQx1/mJm5zCN4uiB4Yf1rMAHAr3lDRnkMMGL?= =?iso-8859-1?Q?yvbwwZys9kHuUx9tv01M4/+NA725k/1muQWb02Tcx4G4dHFmH2Igsz9+Ve?= =?iso-8859-1?Q?7LO2hH1gVb39Qr+L6vYW/VXTQhctXhovcx69tTgwdgu7OQaKLmkzlRQK3u?= =?iso-8859-1?Q?45cMRAdanub0uU0b9eAhyiPjQ+9wCx/dK0uvJFv0xbhS6VazYwuuNUagt9?= =?iso-8859-1?Q?0TQ+7LKaLUoJR/qI1bY0LVOFoL+e9hWrFTYr62HzFOpUwr0MEqf7v5wIFp?= =?iso-8859-1?Q?nDK3yR9XeS4usDxZdzmEN8Uqe82e0hsSvAaKlfSakhgH2oHXBE27V9EsKG?= =?iso-8859-1?Q?+O05PLsHYydpycrPtjc3JXkziiQKRDb7BnLckQIfY/TBCXTjsMSSMn3xGH?= =?iso-8859-1?Q?v0ddni74xacKfIjv2cajee0d9/ffO8HhdRyHS1IfBSEm2wrbbdRFDqknZ8?= =?iso-8859-1?Q?Fs3GdDXlStHYMT2wvf52eEfrtwZxe9Lt2qZ6oDrJVTValiEKymM05Ol2fK?= =?iso-8859-1?Q?F5QuOd1gRoPIfX1Z1kvjrJ+2CGDlfFwqqMoUoW79Ay4GwKlqnFqIltRh6o?= =?iso-8859-1?Q?hcaD1di3IzfIU9/HKQfFmYYeLDd8REoBRg1bybO3Yhd7wdb6HPdNxajP3V?= =?iso-8859-1?Q?ns1ol9ajq2xZbEE71mo9BxCa98jXZkJNIqIB3cuB37cBUXcQ5LTd1OyVpf?= =?iso-8859-1?Q?o3X0Hi+LOpnK/+GOWLukAje8LDJ7cd3NdVWiKwdYeP0P9w4egSxmeytTLR?= =?iso-8859-1?Q?nTlqEEodzCn4/VmzXgtv3NCgmAJ9CPSO8vNNbM1vHohk4959fyTM5TX0Z5?= =?iso-8859-1?Q?+OSvrZTVYAT30/yrmjBEmKOrJF8qNEMq9NSc1cTOCTaSqw0bImEEHMoaAG?= =?iso-8859-1?Q?2g5LJeYwqJo+QHGQlTK/VWFtgjakRJNCHlhf8sh3Bbv5FfyMYrTyjHAlBP?= =?iso-8859-1?Q?eDI7QIbCJURCuBn2D9eHFwcD4mPj7tfJzEwezNjTVGpUNNyzOBav8hB9kH?= =?iso-8859-1?Q?G6mi+2KUw0/N2QZYo+0tPZwKa54SgiphGgwbcAAYIbS+H6mlYyzp9MIbYi?= =?iso-8859-1?Q?PA0S2tfxf5/XiwNLXMshZPgg07IRCemhWmbIJ3j1y9z/MoOnQ3p4KEwJLl?= =?iso-8859-1?Q?gKpGGNd6I8J2vAZlA66ul4uVxUtH6cJ4fZXhohnAK0Rp9eIIdp0mxXBZPK?= =?iso-8859-1?Q?ySznuGH5PHG5RWlx1+PbnBUcA0bZrTWD7h3KNxy7L3PCb1hofzt73WPYX1?= =?iso-8859-1?Q?kzcEoiKD4pujT1snLkrXbl45hoIebL6TpXfGHk7dvprJZc4DpjTUnQNxyD?= =?iso-8859-1?Q?EZU0FHsuA1CdwIBSxDaxQ3lE/3ThPJ32rLJ1dlLcQ3hdYzgMYqC9PSZ887?= =?iso-8859-1?Q?fwAhh8ClQZsUzXYMCM5Qyneahb5/p3jtXSDhyrHLxtOTGBJLpFEz38/+uI?= =?iso-8859-1?Q?hDNO9p8UDlu5VQbcgXpnDH/gKnOY5xUlZ0t4beAHQ3yTbJeDtvBgjDKB3F?= =?iso-8859-1?Q?3Mtgk1NB8XgsCrTuT+XuF4sdc9FDYgWyKNCq8ND62QFOA4zHNTUPnuf2U8?= =?iso-8859-1?Q?IhC0ut5FIiBTeuicIM2ruduW4Kr595bBEZ23tRefq+fT4TZKVgx31QOvLH?= =?iso-8859-1?Q?dWRTFM3CgS6e8J7b/TWMgmQUVCXDHnS1gWo1/gnkc4wyUTQNZVEaagFg?= =?iso-8859-1?Q?=3D=3D?= X-MS-Exchange-CrossTenant-Network-Message-Id: 0d9b8af2-a9aa-48bd-17f0-08dbe78d53de X-MS-Exchange-CrossTenant-AuthSource: MN0PR11MB6059.namprd11.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Nov 2023 16:50:38.8662 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 46c98d88-e344-4ed4-8496-4ed7712e255d X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: 8isd+fpQtwh3Yf7+2A2SSp0+5uXCmlyFNMtbgIFnWfUgcyuXe4/l6PxqCUQDnCLzMj/gApBQSAjuVU2//nTH5A== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR11MB8228 X-OriginatorOrg: intel.com Subject: Re: [Intel-xe] [Intel-gfx] [PATCH] drm/i915: don't use uncore spinlock to protect critical section in vblank X-BeenThere: intel-xe@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel Xe graphics driver List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "intel-gfx@lists.freedesktop.org" , "Coelho, Luciano" , "intel-xe@lists.freedesktop.org" Errors-To: intel-xe-bounces@lists.freedesktop.org Sender: "Intel-xe" On Fri, Nov 17, 2023 at 11:26:44AM +0200, Ville Syrjälä wrote: > On Fri, Nov 17, 2023 at 10:41:43AM +0200, Ville Syrjälä wrote: > > On Fri, Nov 17, 2023 at 08:05:21AM +0000, Coelho, Luciano wrote: > > > Thanks for your comments, Ville! > > > > > > On Fri, 2023-11-17 at 09:19 +0200, Ville Syrjälä wrote: > > > > On Thu, Nov 16, 2023 at 01:27:00PM +0200, Luca Coelho wrote: > > > > > Since we're abstracting the display code from the underlying driver > > > > > (i.e. i915 vs xe), we can't use the uncore's spinlock to protect > > > > > critical sections of our code. > > > > > > > > > > After further inspection, it seems that the spinlock is not needed at > > > > > all and this can be handled by disabling preemption and interrupts > > > > > instead. > > > > > > > > uncore.lock has multiple purposes: > > > > 1. serialize all register accesses to the same cacheline as on > > > > certain platforms that can hang the machine > > > > > > Okay, do you remember which platforms? > > > > HSW is the one I remember for sure being affected. > > Althoguh I don't recall if I ever managed to hang it > > using display registers specifically. intel_gpu_top > > certainly was very good at reproducing the problem. > > > > > I couldn't find any reference to > > > this reason. > > > > If all else fails git log is your friend. > > It seems to be documented in intel_uncore.h. Though that one > mentions IVB instead of HSW for some reason. I don't recall > seeing it on IVB myself, but I suppose it might have been an > issue there as well. How long the problem remained after HSW > I have no idea. Paulo very recently told me that he could easily reproduce the issue on IVB, simply by running 2 glxgears at the same time. > > > > > > Also, the only place where where we take the uncore.lock > > > is in this vblank code I changed, where the only explanation I found > > > was about timing, specifically when using RT-kernels and in very old > > > and slow platforms... (this was added 10 years ago). > > > > > > > > > > 2. protect the forcewake/etc. state > > > > > > > > 1 is relevant here, 2 is not. > > > > > > Okay, good that we have only one known problem. :) and good it is an old one! :) > > > > > > -- > > > Cheers, > > > Luca. > > > > -- > > Ville Syrjälä > > Intel > > -- > Ville Syrjälä > Intel