From: Fei Li <fei1.li@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
<dave.hansen@intel.com>, <gregkh@linuxfoundation.org>,
<tglx@linutronix.de>, <mingo@redhat.com>, <bp@alien8.de>,
<dave.hansen@linux.intel.com>, <hpa@zytor.com>,
<Yu1.Wang@intel.com>, <conghui.chen@intel.com>,
<fengwei.yin@intel.com>
Subject: Re: [PATCH] x86/acrn: Set X86_FEATURE_TSC_KNOWN_FREQ
Date: Wed, 26 Oct 2022 11:32:27 +0800 [thread overview]
Message-ID: <Y1iqS3FuCjPE8icm@louislifei-OptiPlex-7090> (raw)
In-Reply-To: <Y1fjMnX9UOVo2+K5@hirez.programming.kicks-ass.net>
On 2022-10-25 at 15:22:58 +0200, Peter Zijlstra wrote:
> On Tue, Oct 25, 2022 at 04:41:47PM +0800, Fei Li wrote:
> > Avoiding recalibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
> > This patch also removes `inline` for acrn_get_tsc_khz() since
> > it doesn't make sense.
>
Hi Peter
Thanks for your comments.
> Can we have a few words on how this is supposed to work at all?
If the TSC frequency is known from the acrn_get_tsc_khz(),
the TSC frequency does not need to be recalibrated.
We can avoid recalibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
>
> Supposedly the HV is providing host rate through this ACRN CPUID leaf?
ACRN would provide the calibrated TSC frequency, not just the
host rate through this CPUID leaf.
> How does it deal with systems where TSC isn't known stable?
>
prev parent reply other threads:[~2022-10-26 3:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 8:41 Fei Li
2022-10-25 13:22 ` Peter Zijlstra
2022-10-26 3:32 ` Fei Li [this message]
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