RE: [PATCH] whpx: Added support for saving/restoring VM state

[Ivan Shcherbakov]

Hi Paolo,

>What are the differences?  Is it using the XSAVEC/XSAVES ("compacted") format?

I am not very familiar with the format internals, so I briefly checked whether 
I could reuse the general logic from the HVF port. Here's what I got on a 
booted Linux VM:

WHvGetVirtualProcessorXsaveState() returned this block (844 bytes):

7f 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 a0 1f 
00 00 ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 58 65 c8 34 7f 00 00 04 7f 65 c8 34 7f 00 00 44 e1 68 c8 34 7f 
00 00 f8 35 65 c8 34 7f 00 00 ec 4f 65 c8 34 7f 00 00 5c 4f 6a c8 34 7f 00 00 
d0 7d 65 c8 34 7f 00 00 3c 6a 67 c8 34 7f 00 00 64 90 67 c8 34 7f 00 00 9c 0c 
78 c8 34 7f 00 00 3c 6a 67 c8 34 7f 00 00 40 60 65 c8 34 7f 00 00 5c 4f 6a c8 
34 7f 00 00 d0 7d 65 c8 34 7f 00 00 f8 35 65 c8 34 7f 00 00 ec 4f 65 c8 34 7f 
00 00 70 3d 66 cb 34 7f 00 00 00 00 00 00 00 00 00 00 69 00 65 00 6f 00 20 00 
00 00 00 00 00 00 00 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 ff 00 
00 00 ff ff 00 00 00 00 00 00 00 00 ff ff 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 02 00 00 00 0c 00 00 00 05 00 00 00 22 00 00 00 05 00 00 00 10 00 
00 00 05 00 00 00 22 00 00 00 10 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 03 00 00 00 00 00 00 00 
07 00 00 00 00 00 00 80 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Passing it to x86_cpu_xrstor_all_areas()/x86_cpu_xsave_all_areas() changed the 
following values:

0x0000001C: ff ff -> 00 00
0x00000208: 07 -> 00
0x0000020F: 80 -> 00

Trying to pass the updated block to WHvSetVirtualProcessorXsaveState() just 
made it reject the entire block with error c0350005 (generic "invalid 
parameter").

I haven't looked too deep into it, since just saving the state "as is" is 
sufficient to get the snapshots working. If there is something obvious I 
missed, I can give it another brief try.

Best,
Ivan