From:   Thomas Gleixner <tglx@linutronix.de>
To:     zhenwei pi <pizhenwei@bytedance.com>, pbonzini@redhat.com
Cc:     kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org,
        zhenwei pi <pizhenwei@bytedance.com>
Subject: Re: [PATCH v2 2/2] KVM: x86: use x86_get_freq to get freq for kvmclock
In-Reply-To: <20211201024650.88254-3-pizhenwei@bytedance.com>
References: <20211201024650.88254-1-pizhenwei@bytedance.com>
 <20211201024650.88254-3-pizhenwei@bytedance.com>
Date:   Thu, 02 Dec 2021 03:48:41 +0100
Message-ID: <877dcn7md2.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, Dec 01 2021 at 10:46, zhenwei pi wrote:
> If the host side supports APERF&MPERF feature, the guest side may get
> mismatched frequency.
>
> KVM uses x86_get_cpufreq_khz() to get the same frequency for guest side.
>
> Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
> ---
>  arch/x86/kvm/x86.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5a403d92833f..125ed3c8b21a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -8305,10 +8305,8 @@ static void tsc_khz_changed(void *data)
>  
>  	if (data)
>  		khz = freq->new;
> -	else if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
> -		khz = cpufreq_quick_get(raw_smp_processor_id());
>  	if (!khz)
> -		khz = tsc_khz;
> +		khz = x86_get_cpufreq_khz(raw_smp_processor_id());

my brain compiler tells me that this is broken.