Re: [Xen-devel] [PATCH for 4.5] x86/viridian: Freeze time reference counter when domain is paused

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 10 October 2014 14:02
> To: Paul Durrant
> Cc: Andrew Cooper; xen-devel@xxxxxxxxxxxxxxxxxxxx; Keir (Xen.org)
> Subject: Re: [PATCH for 4.5] x86/viridian: Freeze time reference counter
> when domain is paused
> 
> >>> On 10.10.14 at 11:07, <paul.durrant@xxxxxxxxxx> wrote:
> > @@ -460,11 +495,12 @@ static int viridian_load_domain_ctxt(struct
> domain *d, hvm_domain_context_t *h)
> >  {
> >      struct hvm_viridian_domain_context ctxt;
> >
> > -    if ( hvm_load_entry(VIRIDIAN_DOMAIN, h, &ctxt) != 0 )
> > +    if ( hvm_load_entry_zeroextend(VIRIDIAN_DOMAIN, h, &ctxt) != 0 )
> >          return -EINVAL;
> >
> > -    d->arch.hvm_domain.viridian.hypercall_gpa.raw = ctxt.hypercall_gpa;
> > -    d->arch.hvm_domain.viridian.guest_os_id.raw   = ctxt.guest_os_id;
> > +    d->arch.hvm_domain.viridian.time_ref_count.val =
> ctxt.time_ref_count;
> > +    d->arch.hvm_domain.viridian.hypercall_gpa.raw  = ctxt.hypercall_gpa;
> > +    d->arch.hvm_domain.viridian.guest_os_id.raw    = ctxt.guest_os_id;
> 
> Is loading zero here correct when migration comes from an older
> hypervisor?

The enlightenment can only be enabled in 4.5 so, providing this patch goes into 
4.5, there is no compatibility problem.

> 
> > @@ -706,6 +710,11 @@ void domain_shutdown(struct domain *d, u8
> reason)
> >          v->paused_for_shutdown = 1;
> >      }
> >
> > +#ifdef CONFIG_X86
> > +    if ( has_viridian_time_ref_count(d) )
> > +        viridian_time_ref_count_freeze(d);
> > +#endif
> > +
> 
> So in the description you say "but only if the domain is not shutting
> down" - how does the above change fit that? Or is that comment
> ambiguous whether it refers to both the freezing and thawing or only
> the thawing?

It only applies to thawing. Sorry for the ambiguity.

  Paul

> 
> Jan


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