Re: [Xen-devel] [PATCH] x86/cpuid: Avoid unconditionally clobbering ITSC for guests

2016-05-17 Thread Wei Liu
On Mon, May 16, 2016 at 05:59:15PM +0100, Andrew Cooper wrote: > In general, Invariant TSC is not a feature which can be advertised to guests, > because it cannot be guaranteed across migrate. domain_cpuid() goes so far as > to deliberately clobber the feature flag under a number of

Re: [Xen-devel] [PATCH] x86/cpuid: Avoid unconditionally clobbering ITSC for guests

2016-05-17 Thread Jan Beulich
>>> On 16.05.16 at 18:59, wrote: > In general, Invariant TSC is not a feature which can be advertised to guests, > because it cannot be guaranteed across migrate. domain_cpuid() goes so far as > to deliberately clobber the feature flag under a number of circumstances.

[Xen-devel] [PATCH] x86/cpuid: Avoid unconditionally clobbering ITSC for guests

2016-05-16 Thread Andrew Cooper
In general, Invariant TSC is not a feature which can be advertised to guests, because it cannot be guaranteed across migrate. domain_cpuid() goes so far as to deliberately clobber the feature flag under a number of circumstances. Because ITSC is absent from the static {pv,hvm}_featureset masks,