Re: [PATCH 2/2] x86/MCE: Always save MCA_{ADDR,MISC,SYND} register contents

[Luck, Tony]

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, âIA32_MCi_ADDR
  MSRâ).  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