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Date: Wed, 10 Aug 2022 19:49:00 -0700 From: ira.weiny@...el.com To: Rik van Riel <riel@...riel.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...el.com> Cc: Ira Weiny <ira.weiny@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org, kernel-team@...com Subject: [PATCH 0/3] Print CPU at segfault time From: Ira Weiny <ira.weiny@...el.com> Changes from RFC: Drop patch 1 as I misunderstood the code and it is not needed for this use case Combine patch 2 and 5 into a patch 3 which stores the CPU only for page faults Rik reported that the knowledge of which CPU's are seeing faults can help in determining which CPUs are failing in a large data center.[1] Storing the CPU at exception entry time allows this print to report the CPU which actually took the exception. This still may not be the CPU which is failing but it should be closer. Dave and Boris recognized that the auxiliary pt_regs work I did for the PKS series could help to store this value and avoid passing the CPU throughout the fault handler call stack. The patches I sent for RFC had a lot more overhead than is needed to report the CPU in a page fault.[2] After the discussions the generic save/restore of the auxiliary pt_regs is overkill for the current use case. Skip that overhead and only store the CPU in the page fault path. [1] https://lore.kernel.org/all/20220805101644.2e674553@imladris.surriel.com/ [2] https://lore.kernel.org/lkml/20220805173009.3128098-1-ira.weiny@intel.com/ Ira Weiny (2): x86/entry: Add auxiliary pt_regs space x86/mm: Store CPU info on exception entry Rik van Riel (1): x86,mm: print likely CPU at segfault time arch/x86/Kconfig | 4 ++++ arch/x86/entry/calling.h | 19 +++++++++++++++++++ arch/x86/entry/entry_64.S | 22 ++++++++++++++++++++++ arch/x86/entry/entry_64_compat.S | 6 ++++++ arch/x86/include/asm/ptrace.h | 19 +++++++++++++++++++ arch/x86/kernel/asm-offsets_64.c | 15 +++++++++++++++ arch/x86/kernel/head_64.S | 6 ++++++ arch/x86/mm/fault.c | 18 ++++++++++++++++++ 8 files changed, 109 insertions(+) base-commit: d4252071b97d2027d246f6a82cbee4d52f618b47 -- 2.35.3
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