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Re: [PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken mdelay

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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

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[PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken mdelay yu.c.chen@intel.com - 2016-05-06 05:30 +0200
  Re: [PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken  mdelay Thomas Gleixner <tglx@linutronix.de> - 2016-05-06 11:50 +0200
    Re: [PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken  mdelay Thomas Gleixner <tglx@linutronix.de> - 2016-05-06 12:00 +0200
      RE: [PATCH] x86, tsc: Fix tsc ratio calibration to avoid broken  mdelay "Chen, Yu C" <yu.c.chen@intel.com> - 2016-05-06 14:50 +0200
  [tip:x86/urgent] x86/tsc: Read all ratio bits from  MSR_PLATFORM_INFO tip-bot for Chen Yu <tipbot@zytor.com> - 2016-05-06 12:00 +0200

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