linux-kernel - Re: [PATCH 08/15] KVM: VMX: Configure list of user return MSRs at module init

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Date:   Tue, 11 May 2021 20:10:05 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
        Reiji Watanabe <reijiw@...gle.com>
Subject: Re: [PATCH 08/15] KVM: VMX: Configure list of user return MSRs at
 module init

On Tue, May 11, 2021, Maxim Levitsky wrote:
> On Mon, 2021-05-10 at 15:13 +0000, Sean Christopherson wrote:
> > On Mon, May 10, 2021, Maxim Levitsky wrote:
> > > On Tue, 2021-05-04 at 10:17 -0700, Sean Christopherson wrote:
> > > > @@ -6929,18 +6942,10 @@ static int vmx_create_vcpu(struct kvm_vcpu *vcpu)
> > > >  			goto free_vpid;
> > > >  	}
> > > >  
> > > > -	BUILD_BUG_ON(ARRAY_SIZE(vmx_uret_msrs_list) != MAX_NR_USER_RETURN_MSRS);
> > > > +	for (i = 0; i < vmx_nr_uret_msrs; ++i) {
> > > > +		vmx->guest_uret_msrs[i].data = 0;
> > > >  
> > > > -	for (i = 0; i < ARRAY_SIZE(vmx_uret_msrs_list); ++i) {
> > > > -		u32 index = vmx_uret_msrs_list[i];
> > > > -		int j = vmx->nr_uret_msrs;
> > > > -
> > > > -		if (kvm_probe_user_return_msr(index))
> > > > -			continue;
> > > > -
> > > > -		vmx->guest_uret_msrs[j].slot = i;
> > > I don't see anything initalizing the .slot after this patch.
> > > Now this code is removed later which masks this bug, 
> > > but for the bisect sake, I think that this patch 
> > > should still be fixed.
> > 
> > Egad, indeed it's broken.  I'll retest the whole series to verify the other
> > patches will bisect cleanly.
> > 
> > Nice catch!
> > 
> Thanks!

Unfortunately this made it's way to Linus before I could fix my goof.  Fingers
crossed no one is unfortunate enough to land on this while bisecting...