[PATCH 0/5][RFC] lwp: adding support for AMD lightweight profiling

[Wei Huang <wei.huang2@amd.com>]

Hi,

The following patch set is to enable lightweight profiling for AMD CPUs. 
Note that they are targeted at Xen-4.1 beyond. But I am posting them now 
for comments. The changes are summarized as the following:

1. The patches extend CPUID leaves (in tools) from 0x80000008 to 
0x8000001c. The idea of this change was borrowed from Christoph Egger's 
nested virtualization tools patch.
2. Because TS doesn't track LWP xsave area, we have to save and restore 
this area on every domain_context_switch. For this purpose, we add a new 
parameter in xsave/xrstor function to specify the save/restore area in 
EAX:EDX. We check some bits (xsave_read.hdr and lwp_cfg MSR) to avoid 
unnecessary save/restore. A similar idea was proposed to Linux kernel by 
Hans Rosenfeld.
3. Inside svm.c, we keep track of lwp_cfg MSR for various purposes. In 
comparison, lwp_cbaddr is handed by xsave/xrstor automatically.

Please comment. I would start to submit a formal one after 4.1 is closed.

Thanks,
-Wei