Re: [PATCH 8/9] xen/arch/x86: use is_hardware_domain instead of domid == 0

Andrew Cooper
Fri, 12 Apr 2013 16:48:33 -0000

On 12/04/13 16:49, Ian Campbell wrote:
> On Fri, 2013-04-12 at 16:41 +0100, Keir Fraser wrote:
>> We could get rid of this not-always-faulting-cpuid hack in the
>> hypervisor altogether, if we could provide a paravirtualised interface
>> that guarantees access to the real CPUID space, for the toolstack to
>> use.
> Doesn''t XCP have a patch which allows access to the non-levelled
cpuid
> values for the toolstacks benefit? Andy C CCd...
>
>

XCP/XenServer has a specific patch which records the real CPUID values
before applying the MSRs for feature masking, which can then subsequently

This allows the toolstack to recalculate the host level parity bits
correctly whenever a host is added or removed from the pool, without
suffering the problems of getting into a diminishing subset of features
as slightly heterogeneous hardware is moved in and out of the pool.

The patch is currently in the state of "Needing to be cleaned up for
upstream" and is in my todo list (albeit quite far down given some
recent Xen crashes found during stress testing)

I can up its priority if there is a need for it.

~Andrew