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 luiakZF1 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 11/20/25 14:15, Matthew Brost wrote: > On Thu, Nov 20, 2025 at 01:59:09PM +1100, Balbir Singh wrote: >> On 11/20/25 13:50, Balbir Singh wrote: >>> On 11/20/25 13:40, Matthew Brost wrote: >>>> On Wed, Nov 12, 2025 at 10:52:43AM +1100, Balbir Singh wrote: >>>>> On 11/12/25 10:43, Andrew Morton wrote: >>>>>> On Thu, 9 Oct 2025 03:33:33 -0700 Matthew Brost wrote: >>>>>> >>>>>>>>>> This patch series introduces support for Transparent Huge Page >>>>>>>>>> (THP) migration in zone device-private memory. The implementation enables >>>>>>>>>> efficient migration of large folios between system memory and >>>>>>>>>> device-private memory >>>>>>>>> >>>>>>>>> Lots of chatter for the v6 series, but none for v7. I hope that's a >>>>>>>>> good sign. >>>>>>>>> >>>>>>>> >>>>>>>> I hope so too, I've tried to address the comments in v6. >>>>>>>> >>>>>>> >>>>>>> Circling back to this series, we will itegrate and test this version. >>>>>> >>>>>> How'd it go? >>>>>> >>>> >>>> My apologies for the delay—I got distracted by other tasks in Xe (my >>>> driver) and was out for a bit. Unfortunately, this series breaks >>>> something in the existing core MM code for the Xe SVM implementation. I >>>> have an extensive test case that hammers on SVM, which fully passes >>>> prior to applying this series, but fails randomly with the series >>>> applied (to drm-tip-rc6) due to the below kernel lockup. >>>> >>>> I've tried to trace where the migration PTE gets installed but not >>>> removed or isolate a test case which causes this failure but no luck so >>>> far. I'll keep digging as I have time. >>>> >>>> Beyond that, if I enable Xe SVM + THP, it seems to mostly work (though >>>> the same issue as above eventually occurs), but I do need two additional >>>> core MM patches—one is new code required for Xe, and the other could be >>>> considered a bug fix. Those patches can included when Xe merges SVM THP >>>> support but we need at least not break Xe SVM before this series merges. >>>> >>>> Stack trace: >>>> >>>> INFO: task kworker/u65:2:1642 blocked for more than 30 >>>> seconds. >>>> [ 212.624286] Tainted: G S W 6.18.0-rc6-xe+ #1719 >>>> [ 212.630561] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" >>>> disables this message. >>>> [ 212.638285] task:kworker/u65:2 state:D stack:0 pid:1642 >>>> tgid:1642 ppid:2 task_flags:0x4208060 flags:0x00080000 >>>> [ 212.638288] Workqueue: xe_page_fault_work_queue >>>> xe_pagefault_queue_work [xe] >>>> [ 212.638323] Call Trace: >>>> [ 212.638324] >>>> [ 212.638325] __schedule+0x4b0/0x990 >>>> [ 212.638330] schedule+0x22/0xd0 >>>> [ 212.638331] io_schedule+0x41/0x60 >>>> [ 212.638333] migration_entry_wait_on_locked+0x1d8/0x2d0 >>>> [ 212.638336] ? __pfx_wake_page_function+0x10/0x10 >>>> [ 212.638339] migration_entry_wait+0xd2/0xe0 >>>> [ 212.638341] hmm_vma_walk_pmd+0x7c9/0x8d0 >>>> [ 212.638343] walk_pgd_range+0x51d/0xa40 >>>> [ 212.638345] __walk_page_range+0x75/0x1e0 >>>> [ 212.638347] walk_page_range_mm+0x138/0x1f0 >>>> [ 212.638349] hmm_range_fault+0x59/0xa0 >>>> [ 212.638351] drm_gpusvm_get_pages+0x194/0x7b0 [drm_gpusvm_helper] >>>> [ 212.638354] drm_gpusvm_range_get_pages+0x2d/0x40 [drm_gpusvm_helper] >>>> [ 212.638355] __xe_svm_handle_pagefault+0x259/0x900 [xe] >>>> [ 212.638375] ? update_load_avg+0x7f/0x6c0 >>>> [ 212.638377] ? update_curr+0x13d/0x170 >>>> [ 212.638379] xe_svm_handle_pagefault+0x37/0x90 [xe] >>>> [ 212.638396] xe_pagefault_queue_work+0x2da/0x3c0 [xe] >>>> [ 212.638420] process_one_work+0x16e/0x2e0 >>>> [ 212.638422] worker_thread+0x284/0x410 >>>> [ 212.638423] ? __pfx_worker_thread+0x10/0x10 >>>> [ 212.638425] kthread+0xec/0x210 >>>> [ 212.638427] ? __pfx_kthread+0x10/0x10 >>>> [ 212.638428] ? __pfx_kthread+0x10/0x10 >>>> [ 212.638430] ret_from_fork+0xbd/0x100 >>>> [ 212.638433] ? __pfx_kthread+0x10/0x10 >>>> [ 212.638434] ret_from_fork_asm+0x1a/0x30 >>>> [ 212.638436] >>>> >>> >>> Hi, Matt >>> >>> Thanks for the report, two questions >>> >>> 1. Are you using mm/mm-unstable, we've got some fixes in there (including fixes to remove_migration_pmd()) > > remove_migration_pmd - This is a PTE migration entry. > I don't have your symbols, I thought we were hitting, the following condition in the walk if (thp_migration_supported() && pmd_is_migration_entry(pmd)) { But sounds like you are not, PMD/THP has not been enabled in this case >>> - Generally a left behind migration entry is a symptom of a failed migration that did not clean up >>> after itself. > > I'm on drm-tip as I generally need the latest version of my driver > because of the speed we move at. > > Yes, I agree it looks like somehow a migration PTE is not getting > properly removed. > > I'm happy to cherry pick any patches that you think might be helpful > into my tree. > Could you try the mm/mm-new tree with the current xe driver? In general, w.r.t failure, I would check for the following 1. Are the dst_pfns in migrate_vma_pages() setup correctly by the device driver? 2. Any failures in folio_migrate_mapping()? 3. In migrate_vma_finalize() check to see if remove_migration_ptes() failed If (3) fails that will explain the left over migration entries >>> 2. The stack trace is from hmm_range_fault(), not something that this code touches. >>> > > Agree this is a symptom of the above issue. > >>> The stack trace shows your code is seeing a migration entry and waiting on it. >>> Can you please provide a reproducer for the issue? In the form of a test in hmm-tests.c >>> > > That will be my plan. Right now I'm opening my test up which runs 1000s > of variations of SVM tests and the test that hangs is not consistent. > Some of these are threaded or multi-process so it might possibly be a > timing issue which could be hard to reproduce in hmm-tests.c. I'll do my > best here. > >>> Have you been able to bisect the issue? >> > > That is my next step along with isolating a test case. > >> Also could you please try with 10b9feee2d0d ("mm/hmm: populate PFNs from PMD swap entry") >> reverted? >> > > I can try but I highly doubt this is related. The hanging HMM code in is > PTE walk step after this, also I am not even enabling THP device pages > in my SVM code to reproduce this. > Thanks, do regular hmm-tests pass for you in that setup/environment? Balbir > Matt > >>> >>> Balbir >>> >>> >>>> Matt >>>> >>>>>> Balbir, what's the status here? It's been a month and this series >>>>>> still has a "needs a new version" feeling to it. If so, very soon >>>>>> please. >>>>>> >>>>> >>>>> I don't think this needs a new revision, I've been testing frequently >>>>> at my end to see if I can catch any regressions. I have a patch update for >>>>> mm-migrate_device-add-thp-splitting-during-migration.patch, it can be applied >>>>> on top or I can send a new version of the patch. I was waiting >>>>> on any feedback before I sent the patch out, but I'll do it now. >>>>> >>>>>> TODOs which I have noted are >>>>>> >>>>>> https://lkml.kernel.org/r/aOePfeoDuRW+prFq@lstrano-desk.jf.intel.com >>>>> >>>>> This was a clarification on the HMM patch mentioned in the changelog >>>>> >>>>>> https://lkml.kernel.org/r/CABzRoyZZ8QLF5PSeDCVxgcnQmF9kFQ3RZdNq0Deik3o9OrK+BQ@mail.gmail.com >>>>> >>>>> That's a minor comment on not using a temporary declaration, I don't think we need it, let me know if you feel strongly >>>>> >>>>>> https://lkml.kernel.org/r/D2A4B724-E5EF-46D3-9D3F-EBAD9B22371E@nvidia.com >>>>> >>>>> I have a patch for this, which I posted, I can do an update and resend it if required (the one mentioned above) >>>>> >>>>>> https://lkml.kernel.org/r/62073ca1-5bb6-49e8-b8d4-447c5e0e582e@ >>>>>> >>>>> >>>>> I can't seem to open this >>>>> >>>>>> plus a general re-read of the >>>>>> mm-migrate_device-add-thp-splitting-during-migration.patch review >>>>>> discussion. >>>>>> >>>>> That's the patch I have >>>>> >>>>> Thanks for following up >>>>> Balbir >>> >>