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Fri, 8 Aug 2025 18:52:40 +0000 Message-ID: <39edf291-d842-4ae1-b988-76dc3688673b@intel.com> Date: Fri, 8 Aug 2025 11:52:39 -0700 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 2/2] x86/fpu: Update the debug flow for x86_task_fpu() To: Oleg Nesterov CC: "Lai, Yi" , Dave Hansen , , Borislav Petkov , "H . Peter Anvin" , Thomas Gleixner , Ingo Molnar , Dave Hansen , Sean Christopherson , "Peter Zijlstra" , Vignesh Balasubramanian , Rick Edgecombe , "Chang S . 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would always fail in the scenario reported by Yi Lai. > I only meant that the PF_USER_WORKER check in x86_task_fpu() is not > correct right now. > Yes, agreed. >> However, independent of this warning, can xfpregs_get()->sync_fpstate() >> be called in the context of the PF_USER_WORKER thread? > > Probably not but I need to recheck. IIUC, if a PF_USER_WORKER thread encounters a fault, coredump could get triggered in its context. That could cause the above check in sync_fpstate() to pass. Maybe I am missing something? > >> Yeah, I am wondering whether treating PF_USER_WORKER threads as >> equivalent to PF_KTHREAD is truly accurate in the FPU. > > I think it is more or less equivalent but needs some work. In fact > I was thinking about it a long ago, see > https://lore.kernel.org/all/20240606120038.GB22450@redhat.com/ > > I'll try to do something next week. Sure! If it helps, you can add this patch to the end of your series. I am not planning to pursue it any further. Only patch 1 in this series is needed to fix the reported arch_status issue.