Re: [PATCH] acpi, nfit: fix the memory error check in nfit_handle_mce

["Luck, Tony" <tony.luck@intel.com>]

On Fri, Apr 21, 2017 at 01:19:16PM -0700, Dan Williams wrote:
> On Fri, Apr 21, 2017 at 1:16 PM, Luck, Tony <tony.luck@intel.com> wrote:
> >>> > +       if (!(mce->status & 0xef80) == BIT(7))
> >>>
> >>> Can we get a define for this, or a comment explaining all the magic
> >>> that's happening on that one line?
> >>
> >> Yes - also like lkp pointed out, the check isn't correct at all. Let me
> >> figure out what really needs to be done, and I will resend with a better
> >> comment.
> >
> > Needs extra parentheses to make it right. Vishal, sorry I led you astray.
> >
> >         if (!((mce->status & 0xef80) == BIT(7)))
> >
> > The magic is shown in table 15-9 of the Intel Software Developers Manual
> > (but perhaps not well explained there).
> >
> > mce->status in the above code is a value plucked from a machine check
> > bank status register. See figure 15-6 in the SDM.  The important bits for this
> > are {15:0} which are the "MCA Error code".  Table 15-9 shows how these
> > are grouped into types, where the type is defined by the most significant '1'
> > bit in the field (excluding bit 12 which is the Correction Report Filtering bit,
> > see section 15.9.2.1).
> >
> > So if BIT(3) is the most significant bit, the this is a "Generic Cache Hierarchy"
> > error, BIT(4) denotes a TLB error, BIT(7) a Memory error, and so on.
> 
> Ah, ok.
> 
> > Maybe we should have defines in mce.h for them?  It gets a bit more complicated
> > as all the above only applies to Intel branded X86 CPUs ... on AMD different
> > decoding rules apply.
> 
> Yeah, this code is x86_64 generic so should call into helpers that do
> the right thing per cpu type.

Boris: you coded up a "static bool memory_error(struct mce *m)"
function inside the patches for the corrected error thingy.

Perhaps when it goes upstream it should be available for other
users too?

-Tony