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From: Thomas Gleixner <tglx@linutronix.de>
To: Chen Yu <yu.c.chen@intel.com>
Cc: x86@kernel.org, linux-kernel@vger.kernel.org,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	Bin Gao <bin.gao@intel.com>, Len Brown <lenb@kernel.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	"3 . 14+ # 3 . 14+" <stable@vger.kernel.org>
Subject: Re: [PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken mdelay
Date: Fri, 6 May 2016 11:53:25 +0200 (CEST)	[thread overview]
Message-ID: <alpine.DEB.2.11.1605061151050.3540@nanos> (raw)
In-Reply-To: <alpine.DEB.2.11.1605061131580.3540@nanos>


On Fri, 6 May 2016, Thomas Gleixner wrote:
> On Fri, 6 May 2016, yu.c.chen@intel.com wrote:
> > From: Chen Yu <yu.c.chen@intel.com>
> > 
> > Currently we fetch the tsc radio by:
> > ratio = (lo >> 8) & 0x1f;
> > thus get bit8~bit12 of the MSR_PLATFORM_INFO, however according
> > to Intel 64 and IA-32 Architectures Software Developer Manual 35.5,
> > the ratio bit should be bit8~bit15, otherwise we might get incorrect
> > tsc ratio and cause system hang later(mdelay corrupted).
> 
> The resulting issue is that both TSC frequency, which is used for udelay, and
> the lapic timer frequency are wrong. mdelay is just the visible damage caused
> by that.

Aside of that:

> Cc: 3.14+ <stable@vger.kernel.org> # 3.14+

Please use:

Fixes: commit '....'

next time, which identifies the kernel version to which this needs to be
backported and gives a reference to the commit which caused the issue.

Thanks,

	tglx

  reply	other threads:[~2016-05-06  9:55 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-06  3:33 [PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken mdelay yu.c.chen
2016-05-06  9:47 ` Thomas Gleixner
2016-05-06  9:53   ` Thomas Gleixner [this message]
2016-05-06 12:43     ` Chen, Yu C

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