Re: [Xen-devel] [PATCH v15 11/21] x86/VPMU: Interface for setting PMU mode and flags

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 12/04/2014 03:51 AM, Jan Beulich wrote:
> > > > On 03.12.14 at 21:13, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > On 11/27/2014 03:57 AM, Jan Beulich wrote:
> > > > > > On 26.11.14 at 15:32, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > > > On 11/25/2014 08:49 AM, Jan Beulich wrote:
> > > > > > > > On 17.11.14 at 00:07, <boris.ostrovsky@xxxxxxxxxx> wrote:
> > > > > > @@ -244,19 +256,19 @@ void vpmu_initialise(struct vcpu *v)
> > > > > >         switch ( vendor )
> > > > > >         {
> > > > > >         case X86_VENDOR_AMD:
> > > > > > -        if ( svm_vpmu_initialise(v, opt_vpmu_enabled) != 0 )
> > > > > > -            opt_vpmu_enabled = 0;
> > > > > > +        if ( svm_vpmu_initialise(v) != 0 )
> > > > > > +            vpmu_mode = XENPMU_MODE_OFF;
> > > > > >             break;
> > > > > >     
> > > > > >         case X86_VENDOR_INTEL:
> > > > > > -        if ( vmx_vpmu_initialise(v, opt_vpmu_enabled) != 0 )
> > > > > > -            opt_vpmu_enabled = 0;
> > > > > > +        if ( vmx_vpmu_initialise(v) != 0 )
> > > > > > +            vpmu_mode = XENPMU_MODE_OFF;
> > > > > >             break;
> > > > > So this turns off the vPMU globally upon failure of initializing
> > > > > some random vCPU. Why is that? I see this was the case even
> > > > > before your entire series, but shouldn't this be fixed _before_
> > > > > enhancing the whole thing to support PV/PVH?
> > > > Yes, that's probably too strong. Do you want to fix this as an early
> > > > patch (before PV(H)) support gets in? I'd rather do it in the patch that
> > > > moves things into initcalls.
> > > Yes, I think this should be fixed in a prereq patch, thus allowing it
> > > to be easily backported if so desired.
> > I started to make this change and then I realized that the next patch
> > (12/21) is actually already taking care of this problem: most of the
> > *_vpmu_initialise() will be executed as initcalls during host boot and
> > if any of those fail then we do want to disable VPMU globally (those
> > failures would not be VCPU-specific).
> Funny that you say that - it was actually while reviewing that next
> patch when I made that observation: svm_vpmu_initialise() get a
> -ENOMEM return _added_ there for example, which is contrary to
> what I asked for above.

Oh, *that* initialization code (I was looking at vpmu_init()). Yes, VPMU 
should not be turned off there.
-boris


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