Messages in this thread | | | Date | Mon, 1 Aug 2022 09:44:43 -0700 | From | Dan Williams <> | Subject | RE: [PATCH v5] x86/mce: retrieve poison range from hardware |
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Jane Chu wrote: > With Commit 7917f9cdb503 ("acpi/nfit: rely on mce->misc to determine > poison granularity") that changed nfit_handle_mce() callback to report > badrange according to 1ULL << MCI_MISC_ADDR_LSB(mce->misc), it's been > discovered that the mce->misc LSB field is 0x1000 bytes, hence injecting > 2 back-to-back poisons and the driver ends up logging 8 badblocks, > because 0x1000 bytes is 8 512-byte. > > Dan Williams noticed that apei_mce_report_mem_error() hardcode > the LSB field to PAGE_SHIFT instead of consulting the input > struct cper_sec_mem_err record. So change to rely on hardware whenever > support is available. > > Link: https://lore.kernel.org/r/7ed50fd8-521e-cade-77b1-738b8bfb8502@oracle.com > > Reviewed-by: Dan Williams <dan.j.williams@intel.com> > Signed-off-by: Jane Chu <jane.chu@oracle.com> > --- > arch/x86/kernel/cpu/mce/apei.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/cpu/mce/apei.c b/arch/x86/kernel/cpu/mce/apei.c > index 717192915f28..2c7ea0ba9dd7 100644 > --- a/arch/x86/kernel/cpu/mce/apei.c > +++ b/arch/x86/kernel/cpu/mce/apei.c > @@ -29,15 +29,27 @@ > void apei_mce_report_mem_error(int severity, struct cper_sec_mem_err *mem_err) > { > struct mce m; > + int lsb = PAGE_SHIFT; > > if (!(mem_err->validation_bits & CPER_MEM_VALID_PA)) > return; > > + /* > + * Even if the ->validation_bits are set for address mask, > + * to be extra safe, check and reject an error radius '0', > + * and fallback to the default page size. > + */ > + if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK) { > + lsb = __ffs64(mem_err->physical_addr_mask); > + if (lsb == 1)
This was the reason I recommended hweight64 and min_not_zero() as hweight64 does not have the undefined behavior. However, an even better option is to just do:
find_first_bit(&mem_err->physical_addr_mask, PAGE_SHIFT)
...as that trims the result to the PAGE_SHIFT max and handles the zero case.
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