Re: A couple of HVMlite loose ends

[David Vrabel <david.vrabel@citrix.com>]

On 13/01/16 15:49, Roger Pau Monné wrote:
> Hello,
> 
> While working on a HVMlite Dom0 implementation I've found a couple of
> loose ends with the design that I would like to comment because it's not
> clear to me what's the best direction to take.
> 
> 1. HVM CPUID and Dom0.

I think Andy's pending cpu feature series will address this.

> 2. HVM MTRR and Dom0.
> 
> MTRR ranges are initialised from hvmloader, which means that although we
> expose the MTRR functionality to HVMlite guests (and AFAICT the
> functionality is fully complete/usable), the initial state in which a
> guest finds the MTRR ranges is not expected, leading to errors. Again, I
> see three ways to solve this:
> 
>  a) Mask the MTRR functionality from CPUID for HVMlite guests. This
> requires adding a XEN_X86_EMU_MTRR flag to the bitmap introduced in arch
> domain.

I'd favour this approach I think, depending on if any changes were
needed in guests to support this (I assume not?).

Guests should use PAT instead.

David

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