Re: [PATCH] x86/intel_rdt: use rdmsr_safe() to workaround AWS host issue

Tony Luck
2019-01-09T18:42:01Z

On Wed, Jan 9, 2019 at 5:00 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Wed, Jan 09, 2019 at 01:09:31PM +0100, Vitaly Kuznetsov wrote:
> > Hm, why is that? In theory, hypervisors can pass through or emulate the
> > required MSRs...
>
> ...and when the theory becomes reality we'll remove the check.

In practice that may be a long time coming. We don't have many CLOSIDs, or
bits in a cache mask, at the h/w level. If you start trying to
subdivide those resources
to pass a subset to a guest, then you'll quickly find that you have no
flexibility in the
guest to do anything useful. It would only work if you limited to
two, or perhaps three
guests.

-Tony