On 01/25/2013 02:15 PM, H. Peter Anvin wrote:
On 01/25/2013 02:11 PM, H. Peter Anvin wrote:
On 01/25/2013 02:43 AM, tip-bot for Jan Beulich wrote:
Commit-ID: 05fbf4d6fc6a3c0c3e63b77979c9311596716d10
Gitweb: http://git.kernel.org/tip/05fbf4d6fc6a3c0c3e63b77979c9311596716d10
Author: Jan Beulich <jbeul...@suse.com>
AuthorDate: Fri, 2 Nov 2012 14:21:23 +0000
Committer: Ingo Molnar <mi...@kernel.org>
CommitDate: Fri, 25 Jan 2013 09:23:51 +0100
x86/xor: Make virtualization friendly
In virtualized environments, the CR0.TS management needed here
can be a lot slower than anticipated by the original authors of
this code, which particularly means that in such cases forcing
the use of SSE- (or MMX-) based implementations is not desirable
- actual measurements should always be done in that case.
For consistency, pull into the shared (32- and 64-bit) header
not only the inclusion of the generic code, but also that of the
AVX variants.
This patch is wrong and should be dropped. I verified it with the KVM
people that they do NOT want this change. It is a Xen-specific problem.
FWIW: I have dropped this patch from tip:x86/asm.
The bottom line, I guess, is that we need something like
cpu_has_slow_kernel_fpu or something like that, and set it for
specifically affected hypervisors?
Do we know if Hyper-V has performance issues with CR0.TS?
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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