linux-kernel - Re: [PATCH v8 6/7] KVM: X86: Load guest fpu state when accessing MSRs managed by XSAVES

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Message-ID: <20191211020321.GD12845@local-michael-cet-test>
Date:   Wed, 11 Dec 2019 10:03:21 +0800
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Yang Weijiang <weijiang.yang@...el.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, pbonzini@...hat.com,
        jmattson@...gle.com, yu.c.zhang@...ux.intel.com,
        yu-cheng.yu@...el.com
Subject: Re: [PATCH v8 6/7] KVM: X86: Load guest fpu state when accessing
 MSRs managed by XSAVES

On Tue, Dec 10, 2019 at 01:27:48PM -0800, Sean Christopherson wrote:
> On Fri, Nov 01, 2019 at 04:52:21PM +0800, Yang Weijiang wrote:
> > From: Sean Christopherson <sean.j.christopherson@...el.com>
> > 
 
> > -	for (i = 0; i < msrs->nmsrs; ++i)
> > +	for (i = 0; i < msrs->nmsrs; ++i) {
> > +		if (!fpu_loaded && cet_xss &&
> > +		    is_xsaves_msr(entries[i].index)) {
> > +			kvm_load_guest_fpu(vcpu);
> 
> This needs to also check for a non-NULL @vcpu.  KVM_GET_MSR can be called
> on the VM to invoke do_get_msr_feature().
>
Yeah, I need to add the check, thanks!

> > +			fpu_loaded = true;
> > +		}
> >  		if (do_msr(vcpu, entries[i].index, &entries[i].data))
> >  			break;
> > +	}
> > +	if (fpu_loaded)
> > +		kvm_put_guest_fpu(vcpu);
> >  
> >  	return i;
> >  }
> > -- 
> > 2.17.2
> >