Re: [SeaBIOS] [PATCH] Make MTRR region 0xc0000-0x100000 be cached.

[Avi Kivity]

On 01/01/2010 08:23 PM, Kevin O'Connor wrote:
> The current MTRR code in SeaBIOS uses uncached ram for
> 0xc0000-0x100000.  This seems overly pessimistic as "write protect"
> should be sufficient.  (Note, a WP mtrr does not prevent writes - it
> is a caching strategy for memory that can be read-only.)
>
> I'm not sure how much KVM really uses the MTRRs, but if it does honor
> them this should make bootup a bit faster as it will allow caching of
> the SeaBIOS code.
>
> This change also clears all the variable mtrrs, and makes sure all the
> mtrrs are set before they are enabled.

kvm ignores the MTRRs, unless device assignment is enabled, in which 
case it honours them.