Re: [PATCH v7] x86/mce: retrieve poison range from hardware

[Jane Chu]

On 8/3/2022 1:53 AM, Ingo Molnar wrote:
> 
> * Jane Chu <jane.chu@xxxxxxxxxx> wrote:
> 
>> With Commit 7917f9cdb503 ("acpi/nfit: rely on mce->misc to determine
> 
> s/Commit/commit

Maintainers,
Would you prefer a v8, or take care the comment upon accepting the patch?

> 
>> 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@xxxxxxxxxx
>>
>> Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
>> Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
>> Signed-off-by: Jane Chu <jane.chu@xxxxxxxxxx>
>> ---
>>   arch/x86/kernel/cpu/mce/apei.c | 13 ++++++++++++-
>>   1 file changed, 12 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/mce/apei.c b/arch/x86/kernel/cpu/mce/apei.c
>> index 717192915f28..8ed341714686 100644
>> --- a/arch/x86/kernel/cpu/mce/apei.c
>> +++ b/arch/x86/kernel/cpu/mce/apei.c
>> @@ -29,15 +29,26 @@
>>   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;
>>   
>> +	/*
>> +	 * Even if the ->validation_bits are set for address mask,
>> +	 * to be extra safe, check and reject an error radius '0',
>> +	 * and fall back to the default page size.
>> +	 */
>> +	if (mem_err->validation_bits & CPER_MEM_VALID_PA_MASK)
>> +		lsb = find_first_bit((void *)&mem_err->physical_addr_mask, PAGE_SHIFT);
>> +	else
>> +		lsb = PAGE_SHIFT;
>> +
>>   	mce_setup(&m);
>>   	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;
>> +	m.misc = (MCI_MISC_ADDR_PHYS << 6) | lsb;
> 
> LGTM.
> 
> I suppose this wants to go upstream via the tree the bug came from (NVDIMM
> tree? ACPI tree?), or should we pick it up into the x86 tree?

No idea.  Maintainers?

thanks!
-jane

> 
> Thanks,
> 
> 	Ingo