linux-kernel - Re: [PATCH v4 3/3] x86/kvm: Expose AMD Core Perf Extension flag to guests

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Message-ID: <20180205134321.GD27896@flask>
Date:   Mon, 5 Feb 2018 14:43:24 +0100
From:   Radim Krcmar <rkrcmar@...hat.com>
To:     Janakarajan Natarajan <Janakarajan.Natarajan@....com>
Cc:     kvm@...r.kernel.org, x86@...nel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Len Brown <len.brown@...el.com>, Kyle Huey <me@...ehuey.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Borislav Petkov <bp@...e.de>,
        Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>,
        Kan Liang <Kan.liang@...el.com>
Subject: Re: [PATCH v4 3/3] x86/kvm: Expose AMD Core Perf Extension flag to
 guests

2018-01-30 11:32-0600, Janakarajan Natarajan:
> Expose the AMD Core Perf Extension flag to the guests.
> 
> Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@....com>
> ---
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> @@ -365,7 +371,7 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
>  		F(LAHF_LM) | F(CMP_LEGACY) | 0 /*SVM*/ | 0 /* ExtApicSpace */ |
>  		F(CR8_LEGACY) | F(ABM) | F(SSE4A) | F(MISALIGNSSE) |
>  		F(3DNOWPREFETCH) | F(OSVW) | 0 /* IBS */ | F(XOP) |
> -		0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM);
> +		0 /* SKINIT, WDT, LWP */ | F(FMA4) | F(TBM) | f_perfext;

You can just say F(PERFCTR_CORE) here.  The conditional features are
needed when there is a runtime config option for them.  We are
automatically masking features that the host doesn't support,

thanks.

>  
>  	/* cpuid 0xC0000001.edx */
>  	const u32 kvm_cpuid_C000_0001_edx_x86_features =
> -- 
> 2.7.4
>