linux-kernel - Re: [PATCH v6 05/16] KVM: x86/pmu: Introduce the ctrl

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Date:   Tue, 18 May 2021 10:35:09 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Xu, Like" <like.xu@...el.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, weijiang.yang@...el.com,
        Kan Liang <kan.liang@...ux.intel.com>, ak@...ux.intel.com,
        wei.w.wang@...el.com, eranian@...gle.com, liuxiangdong5@...wei.com,
        linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        Like Xu <like.xu@...ux.intel.com>
Subject: Re: [PATCH v6 05/16] KVM: x86/pmu: Introduce the ctrl_mask value for
 fixed counter

On Tue, May 18, 2021 at 03:55:13PM +0800, Xu, Like wrote:
> On 2021/5/17 16:18, Peter Zijlstra wrote:
> > On Tue, May 11, 2021 at 10:42:03AM +0800, Like Xu wrote:
> > > The mask value of fixed counter control register should be dynamic
> > > adjusted with the number of fixed counters. This patch introduces a
> > > variable that includes the reserved bits of fixed counter control
> > > registers. This is needed for later Ice Lake fixed counter changes.
> > > 
> > > Co-developed-by: Luwei Kang <luwei.kang@...el.com>
> > > Signed-off-by: Luwei Kang <luwei.kang@...el.com>
> > > Signed-off-by: Like Xu <like.xu@...ux.intel.com>
> > > ---
> > >   arch/x86/include/asm/kvm_host.h | 1 +
> > >   arch/x86/kvm/vmx/pmu_intel.c    | 6 +++++-
> > >   2 files changed, 6 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> > > index 55efbacfc244..49b421bd3dd8 100644
> > > --- a/arch/x86/include/asm/kvm_host.h
> > > +++ b/arch/x86/include/asm/kvm_host.h
> > > @@ -457,6 +457,7 @@ struct kvm_pmu {
> > >   	unsigned nr_arch_fixed_counters;
> > >   	unsigned available_event_types;
> > >   	u64 fixed_ctr_ctrl;
> > > +	u64 fixed_ctr_ctrl_mask;
> > >   	u64 global_ctrl;
> > >   	u64 global_status;
> > >   	u64 global_ovf_ctrl;
> > > diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
> > > index d9dbebe03cae..ac7fe714e6c1 100644
> > > --- a/arch/x86/kvm/vmx/pmu_intel.c
> > > +++ b/arch/x86/kvm/vmx/pmu_intel.c
> > > @@ -400,7 +400,7 @@ static int intel_pmu_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > >   	case MSR_CORE_PERF_FIXED_CTR_CTRL:
> > >   		if (pmu->fixed_ctr_ctrl == data)
> > >   			return 0;
> > > -		if (!(data & 0xfffffffffffff444ull)) {
> > > +		if (!(data & pmu->fixed_ctr_ctrl_mask)) {
> > Don't we already have hardware with more than 3 fixed counters?
> 
> Yes, so we update this mask based on the value of pmu->nr_arch_fixed_counters:

Yes, I saw that, but the Changelog makes it appear this is only relevant
to ice lake, which I think is not fully correct.