Re: [Xen-devel] [PATCH for-next] x86/svm: Correct vm_event API for descriptor accesses

[Razvan COJOCARU <rcojocaru@xxxxxxxxxxxxxxx>]

On 11/28/19 1:44 PM, Andrew Cooper wrote:
> c/s d0a699a389f1 "x86/monitor: add support for descriptor access events"
> introduced logic looking for what appeared to be exitinfo (not that this
> exists in SVM - exitinfo1 or 2 do), but actually passed the exit IDT vectoring
> information.  There is never any IDT vectoring involved in these intercepts so
> the value passed is always zero.
> 
> In fact, SVM doesn't provide any information, even in exitinfo1 and 2.  Note
> the error in the public API and state that this field is always 0, and drop
> the SVM logic in hvm_monitor_descriptor_access().
> 
> In the SVM vmexit handler itself, optimise the switch statement by observing
> that there is a linear transformation between the SVM exit_reason and
> VM_EVENT_DESC_* values.  (Bloat-o-meter reports 6028 => 5877 for a saving of
> 151 bytes).
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> ---
> CC: Jan Beulich <JBeulich@xxxxxxxx>
> CC: Wei Liu <wl@xxxxxxx>
> CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> CC: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> CC: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
> CC: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
> CC: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
> CC: Adrian Pop <apop@xxxxxxxxxxxxxxx>
> 
> Adrian: Do you recall what information you were attempting to forward from the
> VMCB?  I can't locate anything which would plausibly be interesting.

I think it's safe to go the route you're going (you shouldn't break 
anything).

Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>

(with or without addressing Tamas' comments).


Thanks,
Razvan
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel