Re: [PATCH] x86: Export tsc related information in sysfs

[H. Peter Anvin]

On 05/18/2010 04:58 AM, Peter Zijlstra wrote:
> On Tue, 2010-05-18 at 13:25 +0200, Andi Kleen wrote:
>> On Tue, May 18, 2010 at 11:58:18AM +0200, Peter Zijlstra wrote:
>>> On Sun, 2010-05-16 at 22:06 -0700, Arjan van de Ven wrote:
>>>> look we're not disabling ring 3 tsc. We could, but we don't.
>>>
>>> Maybe we should.
>>
>> That would kill the vsyscall too. Remember it's running in ring 3.
>>
>> That is in theory you could disable it on systems where the vsyscall
>> doesn't use it, but then you would likely break huge amounts of software, 
>> unless you emulate it.
> 
> Well, software shouldn't use it, so breaking it sounds like a fine
> idea ;-)
> 
> Also, a slow emulation is an incentive to actually do the right thing.

The problem is that you throw the baby (vsyscall) out with the bathwater
(user rdtsc).

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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