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SubjectRe: [PATCH 2/2] x86/MCE: Always save MCA_{ADDR,MISC,SYND} register contents
On Mon, Mar 26, 2018 at 10:09:55PM +0200, Borislav Petkov wrote:
> On Mon, Mar 26, 2018 at 08:05:37PM +0000, Ghannam, Yazen wrote:
> > Sure, I can do that. But I didn't think it was necessary because it doesn't hurt
> > to read the registers whether or not the valid bits are set.
>
> No, this needs to be AMD-specific because it will confuse people using
> Intel machines.

Worse than confusion it may even cause a crash on Intel. Quoting the
Intel SDM:

15.3.2.3 IA32_MCi_ADDR MSRs

The IA32_MCi_ADDR MSR contains the address of the code or data memory
location that produced the machine- check error if the ADDRV flag in
the IA32_MCi_STATUS register is set (see Section 15-7, “IA32_MCi_ADDR
MSR”). The IA32_MCi_ADDR register is either not implemented or
contains no address if the ADDRV flag in the IA32_MCi_STATUS register
is clear. When not implemented in the processor, all reads and writes
to this MSR will cause a general protection exception.

Ditto for the MISC register. Please don't read them unless
the ADDRV/MISCV bits are set in the corresponding STATUS
register.

Thanks

-Tony

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