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xen-devel
Re: [Xen-devel] [Patch 2/4] Refining Xsave/Xrestore support
>>> On 28.10.10 at 09:52, Haitao Shan <maillists.shan@xxxxxxxxx> wrote:
> Then I would prefer to write XCR0 unconditionally. Otherwise, I can
> only refer to the approach for handling CR4 switches: reading CR4
> first and checking whether there is a need to write actually.
> But I don't think <a read to XCR0 plus a data comparison> can save any
> compared with one unconditional write to XCR0.
> Are you OK with this?
Depends on the performance expectations of xsetbv and xgetbv
(and its comparison to moves from/to control registers). At least
there's no word in the documentation that xsetbv would be
serializing. I would hope Intel could at least provide approximate
numbers...
Jan
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