linux-kernel - Re: [PATCH v8 07/26] KVM: x86/pmu: Apply "fast" RDPMC only to Intel PMUs

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Message-ID: <96cd6313-6ce4-4d4e-8dd9-78666704b267@linux.intel.com>
Date:   Mon, 13 Nov 2023 09:24:11 +0800
From:   "Mi, Dapeng" <dapeng1.mi@...ux.intel.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Kan Liang <kan.liang@...ux.intel.com>,
        Jim Mattson <jmattson@...gle.com>,
        Jinrong Liang <cloudliang@...cent.com>,
        Aaron Lewis <aaronlewis@...gle.com>,
        Like Xu <likexu@...cent.com>
Subject: Re: [PATCH v8 07/26] KVM: x86/pmu: Apply "fast" RDPMC only to Intel
 PMUs


On 11/10/2023 10:51 PM, Sean Christopherson wrote:
> On Fri, Nov 10, 2023, Dapeng Mi wrote:
>> On 11/10/2023 10:12 AM, Sean Christopherson wrote:
>>> Move the handling of "fast" RDPMC instructions, which drop bits 63:31 of
>> 63:32?
> Oof, yeah.
>
>>> @@ -55,12 +59,17 @@ static struct kvm_pmc *intel_pmc_idx_to_pmc(struct kvm_pmu *pmu, int pmc_idx)
>>>    	}
>>>    }
>>> +static u32 intel_rdpmc_get_masked_idx(struct kvm_pmu *pmu, u32 idx)
>> inline?
> No, for functions that are visible only to the local compilation unit, there's
> no reason to use "inline".  "inline" is just a hint, and modern compilers are
> smart enough to inline functions when appropriate without a hint, e.g. gcc and
> clang inline this on all my configurations.  Compilers may also ignore the hint,
> e.g. KASAN=y tends to produce some really amusing results.
>
> A longer explanation/rant here: https://lore.kernel.org/all/ZAdfX+S323JVWNZC@google.com

Got it. Thanks explanation.