From mboxrd@z Thu Jan  1 00:00:00 1970
From: Avi Kivity <avi@redhat.com>
Subject: Re: [PATCH v3] kvm/fpu: Enable fully eager restore kvm FPU
Date: Sun, 23 Sep 2012 11:03:14 +0200
Message-ID: <505ED052.2070901@redhat.com>
References: <1347437424-3006-1-git-send-email-xudong.hao@intel.com> <20120913162636.GA10191@amt.cnet> <20120913162929.GB10191@amt.cnet> <50520C67.8020609@redhat.com> <403610A45A2B5242BD291EDAE8B37D300FEC2B2A@SHSMSX102.ccr.corp.intel.com> <20120917133058.GA8919@amt.cnet> <403610A45A2B5242BD291EDAE8B37D300FEC34AA@SHSMSX102.ccr.corp.intel.com> <50599D22.5070308@redhat.com> <403610A45A2B5242BD291EDAE8B37D300FEC46D8@SHSMSX102.ccr.corp.intel.com> <505ADFBC.3080109@redhat.com> <403610A45A2B5242BD291EDAE8B37D300FEC51BE@SHSMSX102.ccr.corp.intel.com>
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Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"Zhang, Xiantao" <xiantao.zhang@intel.com>
To: "Hao, Xudong" <xudong.hao@intel.com>
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On 09/21/2012 11:47 AM, Hao, Xudong wrote:
> > -----Original Message-----
> > From: Avi Kivity [mailto:avi@redhat.com]
> > Sent: Thursday, September 20, 2012 5:20 PM
> > To: Hao, Xudong
> > Cc: Marcelo Tosatti; kvm@vger.kernel.org; Zhang, Xiantao
> > Subject: Re: [PATCH v3] kvm/fpu: Enable fully eager restore kvm FPU
> > >> >> On guest entry:
> > >> >>         if (!lazy_fpu_allowed(vcpu))
> > >> >>                 kvm_x86_ops->fpu_activate(vcpu);
> > >> >
> > >>
> > >> But we already have that:
> > >>
> > >> 	if (vcpu->fpu_active)
> > >> 		kvm_load_guest_fpu(vcpu);
> > >>
> > >> so why not manage fpu_active to be always set when needed?  I don't
> > want
> > >> more checks in the entry path.
> > >>
> > > I means add fpu_active() in kvm_set_xcr(), not in guest entry. Then the
> > fpu_active will be set always when guest initialize xstate.
> > >
> > > @@ -574,6 +574,9 @@ int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index,
> > u64 xcr)
> > >         kvm_inject_gp(vcpu, 0);
> > >         return 1;
> > >     }
> > > +   if (!lazy_fpu_allowed(vcpu))
> > > +       kvm_x86_ops->fpu_activate(vcpu);
> > >     return 0;
> > >
> > 
> > And of course on cr4 update.  So a function update_lazy_fpu() to be
> > called from both places is needed.
> > 
>
> Complete consideration, thanks.
>
> So I will define a function update_lazy_fpu(), insert it into kvm_set_xcr() and handle_cr(). Comments?

Sounds good.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.