Re: [PATCH] x86: Add MMIO Stale Data arch_caps to hardware domain

[Jason Andryuk <jandryuk@xxxxxxxxx>]

On Mon, Jul 18, 2022 at 10:18 AM Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 18.07.2022 16:05, Jason Andryuk wrote:
> > Let the hardware domain know about the hardware it is running on.  This
> > allows a linux Dom0 to know that it has the appropriate microcode via
> > FB_CLEAR.  /sys/devices/system/cpu/vulnerabilities/mmio_stale_data
> > changes from:
> > "Vulnerable: Clear CPU buffers attempted, no microcode; SMT Host state
> > unknown"
> > to:
> > "Mitigation: Clear CPU buffers; SMT Host state unknown"
> >
> > Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
> > ---
> > Should calculate_host_policy()'s arch_caps mask also be updated?  They
> > are not identical today, but I'm don't know this code to understand why
> > they differ.
>
> I think this wants updating too, yes. I'm afraid I have to leave it to
> Andrew to provide the reasons for the differences between the two.
>
> I would further suggest to also consider adding RRSBA and BHI_NO, even
> if then the title would want adjusting. And finally I'd like to ask to
> add a proper Fixes: tag (or more), as it looks like the updating here
> was simply forgotten when the bits were introduced. Ideally we'd have
> a way for the compiler to remind us of updates being needed (or at
> least be considered) here.

That all sounds good.

Thanks,
Jason