RE: [Xen-devel] [PATCH] Add xsave/xrstor support to Xen

["Cui, Dexuan" <dexuan.cui@xxxxxxxxx>]

Hi Keir,
In the xsave/xrstor patch, I don't use "arch.guest_context.fpu_ctxt" any longer.
I use "arch_vcpu.xsave_area" to save the processor extended states.

Looks this causes trouble for guest's save/restore (including PV guest and HVM 
guest):

On xsave/xrstor-capable host, to support guest's save/restore, Control Panel 
should save/restore the variable-length "xsave_area", but the current hypercall 
XEN_DOMCTL_{get/set}vcpucontext can't transfer the "xsave_area" between Control 
Panel and hypervisor, so a new hypercall is needed for this? Looks it's not 
very easy to make the codes clean... :(

Could you give some suggestions?

Thanks!

-- Dexuan


-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Cui, Dexuan
Sent: 2008年5月28日 20:03
To: Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] [PATCH] Add xsave/xrstor support to Xen

The attached patch adds the support of xsave/xrstor infrastructure for
x86.
xsave/xrstor manages the existing and future processor extended states
in x86 architecture.

The XSAVE/XRSTOR/XGETBV/XSETBV instructions and the Processor Extended
State are defined in the Intel SDMs:
http://www.intel.com/products/processor/manuals/

The basic ideas of the patch are:
1) enable the xsave/xrstor feature when Xen boots;
2) xsave/xrstor the related processor states (i.e., FPU/MMX, SSE) on
vcpu context switch;
3) with the xsave/xrstor feature enabled, Xen doesn't intercept HVM
vcpu's #NM at all, and Xen still intercepts PV vcpu's #NM and forwards
it into PV vcpu if necessary;
4) xsave/xrstor-aware HVM guest is supported in the patch. 

Signed-off-by: Dexuan Cui <dexuan.cui@xxxxxxxxx>

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