Re: [Xen-devel] MTRR on Xen - BIOS use and implications for Linux

[David Vrabel]

tl;dr?

Somewhere in here are some actual questions which I will attempt to
answer. Please try and be more concise in future.

On 16/03/16 20:08, Luis R. Rodriguez wrote:
> Toshi noted a while ago as well that if BIOS/firmware enables MTRR but
> the kernel does not have it enabled one issue might have been any
> MTRRs set up by the BIOS and ensuring the mapping is respected, in
> particular UC settings, this concern is raised above. Another issue
> though is that the kernel would be "unable to verify if a large page
> mapping is aligned with MTRRs" [3]

This is not a relevant concern for Xen guests:   PV guests do not
support superpage mappings and HVM guests never see real MTRRs.

David