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From: Yi Yang <yi.y.yang@intel.com>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: tglx@linutronix.de, mingo@redhat.com,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: [PATCH 2.6.24] x86: add sysfs interface for cpuid module
Date: Wed, 30 Jan 2008 05:56:57 +0800	[thread overview]
Message-ID: <1201643817.12722.30.camel@yangyi-dev.bj.intel.com> (raw)
In-Reply-To: <479F4B99.4060701@zytor.com>

On Tue, 2008-01-29 at 07:51 -0800, H. Peter Anvin wrote:
> Yi Yang wrote:
> > Current cpuid module will create a char device for every logical cpu,
> > when a user cats /dev/cpu/*/cpuid, he/she will enter a limitless loop,
> > the root cause is that cpuid module doesn't decide wether a cpuid level
> > is valid, it just uses an offset to denote cpuid level and take it to
> > cpuid instruction, cpuid instruction will ignore it and return some data
> > 
> > This patch uses sysfs to avoid limitless loop and provide more flexible
> > interface for cpuid, please consider to merge to -mm tree in order to test.
> 
> This is broken.
> 
> Triple broken.
> 
> It's broken, because it doesn't take into account the fact that Intel 
> broke CPUID level 4 and made it "repeating" (neither did the cpuid char 
> device, because it predated the Intel braindamage; I've had a patch for 
> it privately for a while, but didn't push it upstream because paravirt 
> broke it royally and I wanted the situation to settle down.)
level 4 doesn't result in repeating on Intel CPU, cpuid module sets
file offset to level, so cat /dev/cpu/*/cpuid will run cpuid instruction
continuously.


  parent reply	other threads:[~2008-01-30  7:08 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-04 10:10 [linux-pm][PATCH] base: Change power/wakeup output from "" to "unsupported" if wakeup feature isn't supported by a device Yi Yang
2008-01-04 11:48 ` Pavel Machek
2008-01-04 16:09   ` David Brownell
2008-01-04 16:38     ` Alan Stern
2008-01-04 16:52       ` Olivier Galibert
2008-01-04 17:20         ` Oliver Neukum
2008-01-07  2:00           ` Yi Yang
2008-01-07  1:55         ` Yi Yang
2008-01-07  3:49           ` David Brownell
2008-01-07  1:52       ` Yi Yang
2008-01-07  1:37     ` Yi Yang
2008-01-07  1:57       ` Rafael J. Wysocki
2008-01-07  2:05         ` Yi Yang
2008-01-07 16:46           ` Rafael J. Wysocki
2008-01-07  1:21   ` Yi Yang
2008-01-04 16:31 ` David Brownell
2008-01-07  1:51   ` Yi Yang
2008-01-22 23:05 ` [PATCH 2.6.24-rc8] cpufreq: fix obvious condition statement error Yi Yang
2008-01-28 23:14   ` [PATCH 2.6.24] x86: add sysfs interface for cpuid module Yi Yang
2008-01-29  8:44     ` Sam Ravnborg
2008-01-29 22:22       ` Yi Yang
2008-01-30  7:48         ` Sam Ravnborg
2008-01-29 15:51     ` H. Peter Anvin
2008-01-29 17:52       ` Yi Yang
2008-01-30  6:09         ` H. Peter Anvin
2008-01-29 21:56       ` Yi Yang [this message]
2008-01-30  7:17         ` H. Peter Anvin
2008-01-29 22:13           ` Yi Yang
2008-01-30  7:33             ` H. Peter Anvin
2008-01-29 23:41     ` [RFC PATCH 2.6.24] x86: add sysfs interface for cpuid module, try 2 Yi Yang
2008-01-30 17:35       ` H. Peter Anvin
2008-01-31  1:18       ` [PATCH 2.6.24] Add new string functions real_strtoul and change kernel params to use them Yi Yang
2008-01-31 17:03         ` Randy Dunlap
2008-01-31 16:30           ` Yi Yang
2008-02-01  2:47             ` Randy Dunlap
2008-01-31 22:11         ` [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 2 Yi Yang
2008-02-01  0:02           ` [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 3 Yi Yang
2008-02-01  7:36           ` [PATCH 2.6.24] Add new string functions strict_strto* and convert kernel params to use them, take 2 Andrew Morton
2008-02-01  7:39           ` Andrew Morton
2008-02-01  7:40           ` Andrew Morton
2008-02-01 16:31     ` [PATCH 2.6.24] x86: add sysfs interface for cpuid module dean gaudet
2008-02-01 17:56       ` H. Peter Anvin
2008-02-01 17:58         ` H. Peter Anvin
2008-02-14 23:44   ` [PATCH 2.6.25-rc1] cpufreq: fix cpufreq policy refcount imbalance Yi Yang
2008-02-14 23:48   ` Yi Yang
2008-02-15 15:52     ` [linux-pm] " Alan Stern
2008-02-15 18:24       ` Greg KH
2008-02-15 21:01     ` Greg KH
2008-02-25  0:46     ` [PATCH 2.6.25-rc3] cpuidle: fix cpuidle time and usage overflow Yi Yang
2008-02-25 10:15       ` Ingo Molnar
2008-02-25  1:10         ` Yi Yang
2008-03-26  4:46       ` Len Brown

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