Re: [PATCH 1/5] xen/vm_event: Added support for XSETBV events

[Razvan Cojocaru <rcojocaru@bitdefender.com>]

On 05/07/2015 09:03 PM, Andrew Cooper wrote:
> In an effort to be architecture neutral, it might be an idea to have
> something like
> 
> struct vm_event_write_cr {
>     uint64_t index;
>     uint64_t old_val, new_val;
> };
> 
> And have a per-arch index of control registers, such as
> 
> X86_CR0
> X86_CR3
> X86_CR4
> X86_XCR0
> ...
> ARM32_$foo

Staging's vm_event.h looks like this now:

 63 /* CR0 was updated */
 64 #define VM_EVENT_REASON_MOV_TO_CR0              4
 65 /* CR3 was updated */
 66 #define VM_EVENT_REASON_MOV_TO_CR3              5
 67 /* CR4 was updated */
 68 #define VM_EVENT_REASON_MOV_TO_CR4              6
 69 /* An MSR was updated. */
 70 #define VM_EVENT_REASON_MOV_TO_MSR              7

Now, I can change VM_EVENT_REASON_MOV_TO_CR0 to
VM_EVENT_REASON_MOV_TO_CR and use that for all CR and XCR events (well,
only XCR0 now).

Should VM_EVENT_REASON_MOV_TO_MSR become 5, or should we keep backward
compatibility with prior clients and leave a gap?


Thanks,
Razvan Cojocaru