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a="2878718" X-IronPort-AV: E=Sophos;i="6.27,204,1787036400"; d="scan'208";a="2878718" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by fmvoesa104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Nov 2026 09:56:14 -0800 X-CSE-ConnectionGUID: rEdqlWe8TiaPKz4X5TA2Dg== X-CSE-MsgGUID: QHfD0ympSZac0swZMJTAUw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,204,1787036400"; d="scan'208";a="8249114" Received: from soc-cp83kr3.clients.intel.com (HELO [10.122.184.228]) ([10.122.184.228]) by smtpauth.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Nov 2026 09:56:13 -0800 Message-ID: <31278ce8-77ed-4bd2-a237-815cbcc5b489@intel.com> Date: Mon, 9 Nov 2026 11:56:11 -0600 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 04/18] KVM: x86/pmu: Add PMC bitmap accessor helpers To: "Mi, Dapeng" , Yosry Ahmed Cc: Sean Christopherson , Paolo Bonzini , Peter Zijlstra , kvm@vger.kernel.org, Jim Mattson , Andi Kleen , Stephane Eranian , linux-kernel@vger.kernel.org, Mingwei Zhang , Das Sandipan , Shukla Manali , Xudong Hao References: <20261106013927.166209-1-zide.chen@intel.com> <20261106013927.166209-5-zide.chen@intel.com> <531bd088-dc5e-4b2e-953a-6d9d6f14b61e@intel.com> <2aeaac02-368c-40b4-9b2d-feef5e9d9ea8@linux.intel.com> Content-Language: en-US From: "Chen, Zide" In-Reply-To: <2aeaac02-368c-40b4-9b2d-feef5e9d9ea8@linux.intel.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 11/9/2026 1:53 AM, Mi, Dapeng wrote: > > On 11/7/2026 6:35 AM, Yosry Ahmed wrote: >> On Fri, Nov 6, 2026 at 2:19 PM Chen, Zide wrote: >>> >>> >>> On 11/6/2026 1:09 PM, Yosry Ahmed wrote: >>>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h >>>>> index b8875ed5502c..4f192429ed93 100644 >>>>> --- a/arch/x86/include/asm/kvm_host.h >>>>> +++ b/arch/x86/include/asm/kvm_host.h >>>>> @@ -595,7 +595,10 @@ struct kvm_pmu { >>>>> DECLARE_BITMAP(reprogram_pmi, X86_PMC_IDX_MAX); >>>>> atomic64_t __reprogram_pmi; >>>>> }; >>>>> - DECLARE_BITMAP(pmc_exists, X86_PMC_IDX_MAX); >>>>> + union { >>>>> + DECLARE_BITMAP(pmc_exists, X86_PMC_IDX_MAX); >>>>> + u64 pmc_exists64; >>>> __pmc_exists would be more consistent with __reprogam_pmi above. >>> I used the *64 suffix and without '__' to match the cntr_mask/cntr_mask64 >>> and fixed_cntr_mask/fixed_cntr_mask64 pattern in struct x86_pmu_capability >>> (patch 7), whereas __reprogram_pmi used '__' because it is an atomic64_t >>> rather than a scalar mask. >> I don't follow why the '__' prefix is specific to atomics, but anyway, >> I will leave this up to you and Sean. > > Per my understanding, '__' prefix hints this function/variable should not > be accessed directly, it should be accessed via some wrapper helpers. So I > think it depends on if we hope the variable pmc_exists64 should be accessed > directly. Agree, I vote for pmc_exists64 over __pmc_exists. > Thanks. >