Re: [Xen-devel] [PATCH] x86/vtx: Improvements to ept= command line handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.12.18 at 12:15, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 21/12/2018 11:13, Jan Beulich wrote:
>>>>> On 20.12.18 at 18:16, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> +    By default, Xen will use A/D tracking when available in hardware, 
>>> except
>>> +    on Avoton processors affected by erratum AVR41.  Explicitly choosing
>>> +    `ad=0` will disable the use of A/D tracking on capable hardware, 
>>> whereas
>>> +    choosing `ad=1` will cause tracking to be used even on AVR41-affected
>>> +    hardware.
>> Is there any reason for this special casing of the one erratum?
>> Earlier this week I've gone through some spec updates for other
>> purposes, and I've seen some rather frightening EPT A/D errata.
> 
> Which, out of interest?  There are a few, particularly on Skylake, but
> all the problematic ones I'm aware of are fixed in microcode.

I'd have to go through them again, as I didn't pay close attention to
what was said about their status. Are we generally putting ourselves
on the position then that errata don't need working around if there's
a microcode update available? That's a possible position to take, but
not spelled out anywhere.

Jan



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