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Re: [Xen-devel] [PATCH][RFC] FPU LWP 3/5: define new FPU interface func

To: Jan Beulich <JBeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH][RFC] FPU LWP 3/5: define new FPU interface functions: fpu_save, fpu_restore, fpu_reload
From: Wei Huang <wei.huang2@xxxxxxx>
Date: Fri, 15 Apr 2011 10:50:48 -0500
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Will fix.

On 04/15/2011 04:11 AM, Jan Beulich wrote:
On 14.04.11 at 22:38, Wei Huang<wei.huang2@xxxxxxx>  wrote:
Current Xen implementation only support lazy FPU reload via CR0.TS. But
new FPU state isn't always tracked by CR0.TS bit. One example is AMD's
lightweight profiling. With this patch, Xen calls fpu_save() on vcpu
which is being scheduled out and fpu_restore() on vcpu which is being
scheduled in. The nonlazy FPU state is saved and restored in these two
This doesn't match the actual patch - only fpu_restore() is being
added to the context switch path, fpu_save() was there already,
saving both lazy and non-lazy state.

This patch also defines fpu_reload() to handle lazy FPU state when #NM
is triggered.

Signed-off-by: Wei Huang<wei.huang2@xxxxxxx>
+/* Restore VCPU's FPU state when the vcpu is scheduled out */
+void fpu_restore(struct vcpu *v)
The comment ought so say "in" rather than "out".


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