This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


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

To: "Wei Huang" <wei.huang2@xxxxxxx>
Subject: Re: [Xen-devel] [PATCH][RFC] FPU LWP 3/5: define new FPU interface functions: fpu_save, fpu_restore, fpu_reload
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Fri, 15 Apr 2011 10:11:21 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Fri, 15 Apr 2011 02:10:53 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4DA75B57.404@xxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
References: <4DA75B57.404@xxxxxxx>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>>> 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 
> functions.

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".


Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>