linux-kernel - Re: [PATCH 3/3] x86/kvm: Handle all MCA banks

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Message-ID: <20180622184748.GB2377@flask>
Date:   Fri, 22 Jun 2018 20:47:48 +0200
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     KVM <kvm@...r.kernel.org>, Joerg Roedel <joro@...tes.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Tony Luck <tony.luck@...el.com>,
        Yazen Ghannam <Yazen.Ghannam@....com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] x86/kvm: Handle all MCA banks

2018-06-22 20:24+0200, Borislav Petkov:
> On Fri, Jun 22, 2018 at 08:16:04PM +0200, Radim Krčmář wrote:
> > 2018-06-22 11:51+0200, Borislav Petkov:
> > > From: Borislav Petkov <bp@...e.de>
> > > 
> > > Extend the range of MCA banks which get passed to set/get_msr_mce() to
> > > include all the MSRs of the last bank too.
> > > 
> > > Signed-off-by: Borislav Petkov <bp@...e.de>
> > > ---
> > >  arch/x86/kvm/x86.c | 5 +++--
> > >  1 file changed, 3 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > > index 80452b0f0e8c..a7d344823356 100644
> > > --- a/arch/x86/kvm/x86.c
> > > +++ b/arch/x86/kvm/x86.c
> > > @@ -2466,7 +2466,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > >  
> > >  	case MSR_IA32_MCG_CTL:
> > >  	case MSR_IA32_MCG_STATUS:
> > > -	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
> > > +	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_MISC(KVM_MAX_MCE_BANKS) - 1:
> > 
> > It was correct before.  We have 32 banks (KVM_MAX_MCE_BANKS), so the
> > last useable has index 31 and the "- 1" is going to roll over from first
> > MSR of bank 32 to the last MSR of the last bank.
> > 
> > Another way of writing it would be:
> > 
> >  case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_MISC(KVM_MAX_MCE_BANKS - 1):
> 
> Huh?
> 
> This is what I did:
> 
> +   case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_MISC(KVM_MAX_MCE_BANKS) - 1:
> 
> It needs to be MISC because it is the last MSR in the MCA bank and thus
> the highest.

The last MSR is the original "MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1".

"MSR_IA32_MCx_MISC(KVM_MAX_MCE_BANKS) - 1" also covers

  MSR_IA32_MC32_CTL, MSR_IA32_MC32_STATUS, and MSR_IA32_MC32_ADDR

but the maximal valid MSR is MSR_IA32_MC31_MISC.