Re: [Xen-devel] [PATCH v11 for-xen-4.5 13/20] x86/VPMU: Save VPMU state for PV guests during context switch

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 09/23/2014 11:01 AM, Konrad Rzeszutek Wilk wrote:
> On Mon, Sep 22, 2014 at 07:57:54PM -0400, Boris Ostrovsky wrote:
> > Save VPMU state during context switch for both HVM and PV(H) guests.
> >
> > A subsequent patch will make it possible for vpmu_switch_to() to call
> Could you say what is the name of the 'subsequent patch' in the commit
> description please?
It's patch 19 where NMI PMU interrupts are added.

> > vmx_vmcs_try_enter()->vcpu_pause() which needs is_running to be correctly
> > set/cleared. To prepare for that, call context_saved() before vpmu_switch_to()
> > is executed.
> And what ramifications does that have to the guests if one only applied
> patches up to this point?
None. Which is why I decided to make this change in this patch and not 
wait until patch 19.
-boris

> > Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> > ---
> >   xen/arch/x86/domain.c | 20 +++++++++-----------
> >   1 file changed, 9 insertions(+), 11 deletions(-)
> >
> > diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> > index 5e492d8..d7fb99d 100644
> > --- a/xen/arch/x86/domain.c
> > +++ b/xen/arch/x86/domain.c
> > @@ -1495,16 +1495,13 @@ void context_switch(struct vcpu *prev, struct vcpu 
> > *next)
> >       }
> >   
> >       if ( prev != next )
> > -        _update_runstate_area(prev);
> > -
> > -    if ( is_hvm_vcpu(prev) )
> >       {
> > -        if (prev != next)
> > -            vpmu_switch_from(prev, next);
> > +        _update_runstate_area(prev);
> > +        vpmu_switch_from(prev, next);
> > +    }
> >   
> > -        if ( !list_empty(&prev->arch.hvm_vcpu.tm_list) )
> > +    if ( is_hvm_vcpu(prev) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
> >               pt_save_timer(prev);
> > -    }
> >   
> >       local_irq_disable();
> >   
> > @@ -1543,15 +1540,16 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
> >                              !is_hardware_domain(next->domain));
> >       }
> >   
> > -    if ( is_hvm_vcpu(prev) && (prev != next) )
> > -        /* Must be done with interrupts enabled */
> > -        vpmu_switch_to(prev, next);
> > -
> >       context_saved(prev);
> >   
> >       if ( prev != next )
> > +    {
> >           _update_runstate_area(next);
> >   
> > +        /* Must be done with interrupts enabled */
> > +        vpmu_switch_to(prev, next);
> > +    }
> > +
> >       /* Ensure that the vcpu has an up-to-date time base. */
> >       update_vcpu_system_time(next);
> >   
> > --
> > 1.8.1.4
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel

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