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Re: [Xen-devel] [Patch 2/4] Refining Xsave/Xrestore support
| To: | Jan Beulich <JBeulich@xxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [Patch 2/4] Refining Xsave/Xrestore support |
| From: | Haitao Shan <maillists.shan@xxxxxxxxx> |
| Date: | Thu, 28 Oct 2010 10:31:34 +0800 |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx, Weidong Han <weidong.han@xxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Delivery-date: | Wed, 27 Oct 2010 19:32:59 -0700 |
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I don't know but I suppose this won't be a costing instruction at lease no larger than writing to other CRx registers. But agreed that a comparison to minimize the cost would be great. I can add that. Thanks for pointing out. Shan Haitao 2010/10/27 Jan Beulich <JBeulich@xxxxxxxxxx>: >>@@ -1367,6 +1384,8 @@ static void __context_switch(void) >> memcpy(stack_regs, >> &n->arch.guest_context.user_regs, >> CTXT_SWITCH_STACK_BYTES); >>+ if ( cpu_has_xsave ) >>+ set_xcr0(n->arch.xcr0); > > How slow is a write to xcr0? I.e. is it worth checking whether > current xcr0 matches the to be written value? > > Jan > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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