Re: [PATCH 2/3] x86/mce: Define amd_mce_usable_address()

[Shuai Xue]

On 2023/6/14 23:09, Yazen Ghannam wrote:
> On 6/13/2023 10:19 PM, Shuai Xue wrote:
>>
>>
>> On 2023/6/13 22:11, Yazen Ghannam wrote:
>>> Currently, all valid MCA_ADDR values are assumed to be usable on AMD
>>> systems. However, this is not correct in most cases. Notifiers expecting
>>> usable addresses may then operate on inappropriate values.
>>>
>>> Define a helper function to do AMD-specific checks for a usable memory
>>> address. List out all known cases.
>>>
>>> Signed-off-by: Yazen Ghannam <yazen.ghannam@xxxxxxx>
>>> ---
>>>   arch/x86/kernel/cpu/mce/amd.c      | 38 ++++++++++++++++++++++++++++++
>>>   arch/x86/kernel/cpu/mce/core.c     |  3 +++
>>>   arch/x86/kernel/cpu/mce/internal.h |  2 ++
>>>   3 files changed, 43 insertions(+)
>>>
>>> diff --git a/arch/x86/kernel/cpu/mce/amd.c b/arch/x86/kernel/cpu/mce/amd.c
>>> index 1ccfb0c9257f..ca79fa10b844 100644
>>> --- a/arch/x86/kernel/cpu/mce/amd.c
>>> +++ b/arch/x86/kernel/cpu/mce/amd.c
>>> @@ -746,6 +746,44 @@ bool amd_mce_is_memory_error(struct mce *m)
>>>       return legacy_mce_is_memory_error(m);
>>>   }
>>>   +/*
>>> + * AMD systems do not have an explicit indicator that the value in MCA_ADDR is
>>> + * a system physical address. Therefore individual cases need to be detected.
>>> + * Future cases and checks will be added as needed.
>>> + *
>>> + * 1) General case
>>> + *    a) Assume address is not usable.
>>> + * 2) "Poison" errors
>>> + *    a) Indicated by MCA_STATUS[43]: POISON. Defined for all banks except legacy
>>> + *       Northbridge (bank 4).
>>> + *    b) Refers to poison consumption in the Core. Does not include "no action",
>>> + *       "action optional", or "deferred" error severities.
>>> + *    c) Will include a usuable address so that immediate action can be taken.
>>> + * 3) Northbridge DRAM ECC errors
>>> + *    a) Reported in legacy bank 4 with XEC 8.
>>> + *    b) MCA_STATUS[43] is *not* defined as POISON in legacy bank 4. Therefore,
>>> + *       this bit should not be checked.
>> [nit]
>>
>>> + *
>>> + * NOTE: SMCA UMC memory errors fall into case #1.
>>
>> hi, Yazen
>>
>> The address for SMCA UMC memory error is not system physical address, it make sense
>> to be not usable. But how we deal with the SMCA address? The MCE chain like
>> uc_decode_notifier will do a sanity check with mce_usable_address and it will not
>> handle SMCA address.
>>
> 
> Hi Shuai,
> 
> That's correct.
> 
> There isn't a good solution today. This will be handled in future changes.

Hi, Yazen,

Do you have plan to address it? If not, I can help. We meet this problem in our products.

Thanks
Shuai