LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "H. Peter Anvin" <hpa@zytor.com>
To: yi.y.yang@intel.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: Tue, 29 Jan 2008 22:09:51 -0800	[thread overview]
Message-ID: <47A014AF.5040605@zytor.com> (raw)
In-Reply-To: <1201629138.12722.23.camel@yangyi-dev.bj.intel.com>

Yi Yang wrote:
>>
>> 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.)
>>
>> It's broken, because the algorithm used to determine valid CPUID levels 
>> is incorrect; it fails to recognize any CPUID levels other than the main 
>> Intel and AMD ones, e.g. the Transmeta 0x8086xxxx (and sometimes more) 
>> and VIA 0xc000xxxx levels.
> Thank you for pointing out these issues, i think we can let users input
> any cpuid level and output the corresponding cpuid, in this way we can
> avoid to consider cpu differences and left this to userspace. We can
> also consider all the x86 platforms to do cpuid for every one.
> 
>> It's broken, because it is better for the userspace extractor to have 
>> this logic than to stuff it into the kernel, where it sits hogging 
>> unswappable memory at all times.
> It seems not to be very appropriate to let user space consider hardware
> details. /proc/cpuinfo should be an example to justify this.

/proc/cpuinfo represents what the kernel needs to know, so it reflects 
the kernel's interpretation of CPUID.  There is no reason to interpret 
things in the kernel that the kernel doesn't need.

> Is there any user application using /dev/cpu/*/cpuid? if no, i think it
> is feasible to provide an interface in the kernel.

Yes.  It's called x86info, I believe.

	-hpa

  reply	other threads:[~2008-01-30  6:10 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 [this message]
2008-01-29 21:56       ` Yi Yang
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=47A014AF.5040605@zytor.com \
    --to=hpa@zytor.com \
    --cc=akpm@linux-foundation.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=tglx@linutronix.de \
    --cc=yi.y.yang@intel.com \
    --subject='Re: [PATCH 2.6.24] x86: add sysfs interface for cpuid module' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).