linux-kernel - Re: [06/34] perf, kvm: Support the intx/intx_cp modifiers in KVM arch perfmon emulation v2

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Message-ID: <20121023132039.GV16230@one.firstfloor.org>
Date:	Tue, 23 Oct 2012 15:20:39 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, a.p.zijlstra@...llo.nl,
	x86@...nel.org, linux-kernel@...r.kernel.org, acme@...hat.com,
	eranian@...gle.com, Andi Kleen <ak@...ux.intel.com>, avi@...hat.com
Subject: Re: [06/34] perf, kvm: Support the intx/intx_cp modifiers in KVM arch perfmon emulation v2

On Tue, Oct 23, 2012 at 03:05:09PM +0200, Gleb Natapov wrote:
> On Thu, Oct 18, 2012 at 11:19:14PM -0000, Andi Kleen wrote:
> >  static inline u8 fixed_en_pmi(u64 ctrl, int idx)
> > @@ -400,7 +407,7 @@ int kvm_pmu_set_msr(struct kvm_vcpu *vcpu, u32 index, u64 data)
> >  		} else if ((pmc = get_gp_pmc(pmu, index, MSR_P6_EVNTSEL0))) {
> >  			if (data == pmc->eventsel)
> >  				return 0;
> > -			if (!(data & 0xffffffff00200000ull)) {
> > +			if (!(data & 0xfffffffc00200000ull)) {
> >  				reprogram_gp_counter(pmc, data);
> >  				return 0;
> >  			}
> 
> Mask should depend on cpuid bits provided to a guest. SDM says TSX is
> available if CPUID.(EAX=7, ECX=0):RTM[bit 11]=1, or  if
> CPUID.07H.EBX.HLE [bit 4] = 1, so we need to check for this in
> kvm_pmu_cpuid_update() and initialize mask accordingly.

I think it will still error out or do nothing.
So I have doubts the explicit check is worth it.
That should be near enough the hardware.

BTW does the PMU feature still work? I couldn't get it to work at all
with the latest kernel, just when I originally wrote it.

-Andi
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