Re: [Xen-devel] [v2 06/11] vmx: add help functions to support PML

[Tim Deegan <tim@xxxxxxx>]

At 22:57 +0000 on 16 Apr (1429225024), Tian, Kevin wrote:

> > From: Kai Huang [mailto:kai.huang@xxxxxxxxxxxxxxx]
> > +        if ( !p2m_change_type_one(v->domain, gfn, p2m_ram_logdirty,
> > +                    p2m_ram_rw) )
> > +            paging_mark_gfn_dirty(v->domain, gfn);
> 
> Should we handle error from p2m_change_type_one and consequently
> making this flush function non-void?

I don't think we need to return an error, but we should probably 
call mark_dirty here for anything except -EBUSY.

> > +    d->arch.hvm_domain.vmx.status |= VMX_DOMAIN_PML_ENABLED;
> 
> I didn't see how this domain-wise flag is useful. Or if we really
> want to go this way, you also need to clear this flag if vcpu pml
> enable is failed in vcpu hotplug phase, since the flag itself means
> all vcpus of the domain so we must keep this intention in all
> places.

IIUC we need this flag so that we know whether to enable PML on any
new vcpus.  If we fail to enable PML on hotplug, we fail the hotplug
(like for other vcpu bringup errors) so the invariant still holds.

Cheers,

Tim.

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