From: Peter Zijlstra <peterz@infradead.org>
To: Daniel J Blueman <daniel@quora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86: Trust initial offset in architectural TSC-adjust MSRs
Date: Mon, 15 Apr 2024 09:22:08 +0200 [thread overview]
Message-ID: <20240415072208.GE40213@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20240226072533.341382-1-daniel@quora.org>
On Mon, Feb 26, 2024 at 03:25:33PM +0800, Daniel J Blueman wrote:
> When the BIOS configures the architectural TSC-adjust MSRs on secondary
> sockets to correct a constant inter-chassis offset, after Linux brings
> the cores online, the TSC sync check later resets the core-local MSR to
> 0, triggering HPET fallback and leading to performance loss.
>
> Fix this by unconditionally using the initial adjust values read from the
> MSRs. Trusting the initial offsets in this architectural mechanism is a
> better approach than special-casing workarounds for specific platforms.
Given the amount of BIOS fail in general, I'm thinking the number of
machines that have multi-chassis and get this right are far less than
the 'small' systems that get this wrong.
prev parent reply other threads:[~2024-04-15 7:22 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 7:25 [PATCH] x86: Trust initial offset in architectural TSC-adjust MSRs Daniel J Blueman
2024-04-15 7:22 ` Peter Zijlstra [this message]
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