linux-kernel - Re: [PATCH v6 08/16] KVM: x86/pmu: Add IA32_DS

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Date:   Mon, 17 May 2021 15:26:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Like Xu <like.xu@...ux.intel.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
Subject: Re: [PATCH v6 08/16] KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to
 support guest DS

On Tue, May 11, 2021 at 10:42:06AM +0800, Like Xu wrote:
> @@ -3897,6 +3898,8 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr, void *data)
>  {
>  	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
>  	struct perf_guest_switch_msr *arr = cpuc->guest_switch_msrs;
> +	struct debug_store *ds = __this_cpu_read(cpu_hw_events.ds);
> +	struct kvm_pmu *pmu = (struct kvm_pmu *)data;

You can do without the cast, this is C, 'void *' silently casts to any
other pointer type.

>  	u64 intel_ctrl = hybrid(cpuc->pmu, intel_ctrl);
>  	u64 pebs_mask = (x86_pmu.flags & PMU_FL_PEBS_ALL) ?
>  		cpuc->pebs_enabled : (cpuc->pebs_enabled & PEBS_COUNTER_MASK);

> @@ -3931,6 +3934,12 @@ static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr, void *data)
>  	if (!x86_pmu.pebs_vmx)
>  		return arr;
>  
> +	arr[(*nr)++] = (struct perf_guest_switch_msr){
> +		.msr = MSR_IA32_DS_AREA,
> +		.host = (unsigned long)ds,

Using:
		(unsigned long)cpuc->ds;

was too complicated? :-)

> +		.guest = pmu->ds_area,
> +	};
> +
>  	arr[*nr] = (struct perf_guest_switch_msr){
>  		.msr = MSR_IA32_PEBS_ENABLE,
>  		.host = cpuc->pebs_enabled & ~cpuc->intel_ctrl_guest_mask,