From: Avi Kivity <avi@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Joerg Roedel <joerg.roedel@amd.com>,
Dietmar Maurer <dietmar@proxmox.com>, kvm <kvm@vger.kernel.org>
Subject: Re: problem wit svm_get_msr on kvm-kmod-2.6.31.6
Date: Tue, 17 Nov 2009 14:18:17 +0200 [thread overview]
Message-ID: <4B029489.60302@redhat.com> (raw)
In-Reply-To: <4B0273F4.8030204@siemens.com>
On 11/17/2009 11:59 AM, Jan Kiszka wrote:
> Jan Kiszka wrote:
>
>> Dietmar Maurer wrote:
>>
>>> Hi Jan,
>>>
>>> The ubuntu code puts some barrier around the read.
>>>
>>> http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-hardy.git;a=commitdiff;h=198b348d96c9769153e72ca2461f8d841ddff1cc
>>>
>>> You simply override this with your own code - without barrier. Do you think this is correct?
>>>
>> Unless I messed it up again, I "overwrote" it with what is in latest
>> mainline regarding native_read_tsc. But I will check once more.
>>
> The removal of those barriers came with
> 0d12cdd5f883f508d33b85c1bae98fa28987c8c7 (sched: improve sched_clock()
> performance). So this is now an upstream question:
>
> Do we bother about the precision of native_read_tsc in svm or not?
>
>
I doubt it matters. rdtsc will be followed by a return to the guest or
userspace, either of which is expensive enough to swamp any speculation.
--
error compiling committee.c: too many arguments to function
next prev parent reply other threads:[~2009-11-17 12:18 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-16 9:42 problem wit svm_get_msr on kvm-kmod-2.6.31.6 Dietmar Maurer
2009-11-16 10:18 ` Avi Kivity
2009-11-16 10:46 ` Dietmar Maurer
2009-11-16 10:52 ` Avi Kivity
2009-11-16 11:17 ` Dietmar Maurer
2009-11-16 12:01 ` Avi Kivity
2009-11-16 12:03 ` Jan Kiszka
2009-11-16 12:06 ` Avi Kivity
2009-11-16 12:08 ` Jan Kiszka
2009-11-16 12:11 ` Avi Kivity
2009-11-17 8:14 ` Dietmar Maurer
2009-11-17 9:50 ` Jan Kiszka
2009-11-17 9:59 ` Jan Kiszka
2009-11-17 12:18 ` Avi Kivity [this message]
2009-11-17 17:00 ` Jan Kiszka
2009-11-18 7:07 ` Dietmar Maurer
2009-11-17 9:59 ` Dietmar Maurer
2009-11-16 12:02 ` Jan Kiszka
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