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Re: [Xen-devel] A couple of HVMlite loose ends

El 13/01/16 a les 16.54, David Vrabel ha escrit:
> On 13/01/16 15:49, Roger Pau Monnà wrote:
>> 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?).

No, AFAIK PAT works perfectly fine on HVMlite, but IIRC MTRR is
mandatory on amd64 CPUs (although almost nobody uses it).

> Guests should use PAT instead.

This is a far shoot, but HVMlite guests are not required to run with
paging enabled, and as so we should provide ways to set memory
attributes taking that into account IMHO.


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