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Subject: Re: [PATCH v6 08/16] KVM: x86/pmu: Add IA32_DS_AREA MSR emulation to
 support guest DS
To:     Peter Zijlstra <peterz@infradead.org>,
        Like Xu <like.xu@linux.intel.com>
Cc:     Paolo Bonzini <pbonzini@redhat.com>,
        Borislav Petkov <bp@alien8.de>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, weijiang.yang@intel.com,
        Kan Liang <kan.liang@linux.intel.com>, wei.w.wang@intel.com,
        eranian@google.com, liuxiangdong5@huawei.com,
        linux-kernel@vger.kernel.org, x86@kernel.org, kvm@vger.kernel.org
References: <20210511024214.280733-1-like.xu@linux.intel.com>
 <20210511024214.280733-9-like.xu@linux.intel.com>
 <YKJvC5T5UOoCFwhL@hirez.programming.kicks-ass.net>
From:   Andi Kleen <ak@linux.intel.com>
Message-ID: <3b13359c-5b7a-f103-74ff-1f57389db181@linux.intel.com>
Date:   Mon, 17 May 2021 07:50:02 -0700
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On 5/17/2021 6:26 AM, Peter Zijlstra wrote:
> 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.

FWIW doing the C++ like casts for void * is fairly standard C coding 
style. I generally prefer it too for better documentation. K&R is 
written this way.

-Andi (my last email on this topic to avoid any bike shedding)