linux-kernel - Re: [PATCH 8/8] KVM: x86: add SPEC_CTRL and IBPB

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Date:   Tue, 16 Jan 2018 00:40:05 +0000 (UTC)
From:   Eric Wheeler <kvm@...ts.ewheeler.net>
To:     Paolo Bonzini <pbonzini@...hat.com>
cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        rkrcmar@...hat.com, liran alon <liran.alon@...cle.com>,
        jmattson@...gle.com, aliguori@...zon.com,
        thomas lendacky <thomas.lendacky@....com>, dwmw@...zon.co.uk,
        bp@...en8.de, x86@...nel.org
Subject: Re: [PATCH 8/8] KVM: x86: add SPEC_CTRL and IBPB_SUPPORT to MSR and
 CPUID lists

On Sat, 13 Jan 2018, Paolo Bonzini wrote:

> Just add the new MSR at the end of the array.

I'm assuming you meant emulated_msrs[], correct?  


--
Eric Wheeler



> 
> Paolo
> 
> ----- Eric Wheeler <kvm@...ts.ewheeler.net> ha scritto:
> > On Tue, 9 Jan 2018, Paolo Bonzini wrote:
> > 
> > > Expose them to userspace, now that guests can use them.
> > > I am not adding cpufeatures here to avoid having a kernel
> > > that shows spec_ctrl in /proc/cpuinfo and actually has no
> > > support whatsoever for IBRS/IBPB.  Keep the ugly special-casing
> > > for now, and clean it up once the generic arch/x86/ code
> > > learns about them.
> > > 
> > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > > index daa1918031df..4abb37d9f4d8 100644
> > > --- a/arch/x86/kvm/x86.c
> > > +++ b/arch/x86/kvm/x86.c
> > > @@ -1032,6 +1032,7 @@ unsigned int kvm_get_pt_addr_cnt(void)
> > >  	MSR_IA32_RTIT_ADDR1_A, MSR_IA32_RTIT_ADDR1_B,
> > >  	MSR_IA32_RTIT_ADDR2_A, MSR_IA32_RTIT_ADDR2_B,
> > >  	MSR_IA32_RTIT_ADDR3_A, MSR_IA32_RTIT_ADDR3_B,
> > > +	MSR_IA32_SPEC_CTRL,
> > >  };
> > 
> > Hi Paolo,
> > 
> > Thank you for posting this!
> > 
> > I am trying to merge this into 4.14 which does not have 
> > kvm_get_pt_addr_cnt. The rest of the patch commits, but this gets 
> > rejected. Is this a necessary part of the commit?
> > 
> > patching file arch/x86/kvm/cpuid.c
> > Hunk #1 succeeded at 389 (offset -8 lines).
> > Hunk #2 succeeded at 479 (offset -9 lines).
> > Hunk #3 succeeded at 636 (offset -27 lines).
> > patching file arch/x86/kvm/x86.c
> > Hunk #1 FAILED at 1032.
> > 1 out of 1 hunk FAILED -- saving rejects to file arch/x86/kvm/x86.c.rej
> > 
> > ]# cat arch/x86/kvm/x86.c.rej
> > --- arch/x86/kvm/x86.c
> > +++ arch/x86/kvm/x86.c
> > @@ -1032,6 +1032,7 @@
> >  	MSR_IA32_RTIT_ADDR1_A, MSR_IA32_RTIT_ADDR1_B,
> >  	MSR_IA32_RTIT_ADDR2_A, MSR_IA32_RTIT_ADDR2_B,
> >  	MSR_IA32_RTIT_ADDR3_A, MSR_IA32_RTIT_ADDR3_B,
> > +	MSR_IA32_SPEC_CTRL,
> >  };
> >  
> >  static unsigned num_msrs_to_save;
> > 
> > 
> > Thank you for your help!
> > 
> > --
> > Eric Wheeler
> > 
> > 
> > >  
> > >  static unsigned num_msrs_to_save;
> > > -- 
> > > 1.8.3.1
> > > 
> > > 
> > > 
> 
>