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 h8YgFlm2 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Penttilä wrote: >>> >>> On 8/13/25 02:36, Balbir Singh wrote: >>> >>>> On 8/12/25 15:35, Mika Penttilä wrote: >>>>> Hi, >>>>> >>>>> On 8/12/25 05:40, Balbir Singh wrote: ... >> I've not run into this with my testing, let me try with more mTHP sizes enabled. I'll wait on Matthew >> to post his test case or any results, issues seen >> > > I’ve hit this. In the code I shared privately, I split THPs in the > page-collection path. You omitted that in v2 and v3; I believe you’ll > need those changes. The code I'm referring to had the below comment. > > 416 /* > 417 * XXX: No clean way to support higher-order folios that don't match PMD > 418 * boundaries for now — split them instead. Once mTHP support lands, add > 419 * proper support for this case. > 420 * > 421 * The test, which exposed this as problematic, remapped (memremap) a > 422 * large folio to an unaligned address, resulting in the folio being > 423 * found in the middle of the PTEs. The requested number of pages was > 424 * less than the folio size. Likely to be handled gracefully by upper > 425 * layers eventually, but not yet. > 426 */ > > I triggered it by doing some odd mremap operations, which caused the CPU > page-fault handler to spin indefinitely iirc. In that case, a large device > folio had been moved into the middle of a PMD. > > Upstream could see the same problem if the device fault handler enforces > a must-migrate-to-device policy and mremap moves a large CPU folio into > the middle of a PMD. > > I’m in the middle of other work; when I circle back, I’ll try to create > a selftest to reproduce this. My current test is a fairly convoluted IGT > with a bunch of threads doing remap nonsense, but I’ll try to distill it > into a concise selftest. > I ran into this while doing some testing as well, I fixed it in a manner similar to split_folio() for partial unmaps. I will consolidate the folio splits into a single helper and post it with v4. Balbir Singh