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

[Yazen Ghannam]

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.

Thanks,
Yazen