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SubjectRe: [PATCH v2] x86/mce: retrieve poison range from hardware whenever supported
Date
On 7/15/2022 9:50 PM, Dan Williams wrote:
> 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.
>>
>> v1: https://lkml.org/lkml/2022/7/15/1040
>
> This should be "Link:" and it should reference lore.kernel.org by
> msg-id. Lore is maintained by LF infrastructure and the message-id can
> be used to search lore.kernel.org mirrors even if the LF infra is down.
>
> Link: https://lore.kernel.org/r/7ed50fd8-521e-cade-77b1-738b8bfb8502@oracle.com
>

Got it, thanks!

>> Signed-off-by: Jane Chu <jane.chu@oracle.com>
>> ---
>> arch/x86/kernel/cpu/mce/apei.c | 6 +++++-
>> 1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mce/apei.c b/arch/x86/kernel/cpu/mce/apei.c
>> index 717192915f28..a4d5893632e0 100644
>> --- a/arch/x86/kernel/cpu/mce/apei.c
>> +++ b/arch/x86/kernel/cpu/mce/apei.c
>> @@ -29,6 +29,7 @@
>> void apei_mce_report_mem_error(int severity, struct cper_sec_mem_err *mem_err)
>> {
>> struct mce m;
>> + int lsb;
>>
>> if (!(mem_err->validation_bits & CPER_MEM_VALID_PA))
>> return;
>> @@ -37,7 +38,10 @@ void apei_mce_report_mem_error(int severity, struct cper_sec_mem_err *mem_err)
>> m.bank = -1;
>> /* Fake a memory read error with unknown channel */
>> m.status = MCI_STATUS_VAL | MCI_STATUS_EN | MCI_STATUS_ADDRV | MCI_STATUS_MISCV | 0x9f;
>> - m.misc = (MCI_MISC_ADDR_PHYS << 6) | PAGE_SHIFT;
>> + lsb = __builtin_ffs(mem_err->physical_addr_mask) - 1;
>
> Just use the kernel's __ffs64() which does not require the substraction

Will do.

> fixup, and you can assume that physical_address_mask is non-zero just
> like trace_extlog_mem_event() does.

I guess to me, a more convincing evidence is
/* Error grain */
if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK)
e->grain = ~mem_err->physical_addr_mask + 1;
in ghes_edac_report_mem_error().

>
>> + if (lsb <= 0)
>> + lsb = PAGE_SHIFT;
>
> This fixup can then be removed as well.
>
> After the above comments are addressed you can add:
>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>

Thanks!
-jane
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