Re: [Xen-devel] [PATCH v4 2/2] xen/vm-events: Move parts of monitor_domctl code to common-side.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.02.16 at 09:13, <czuzu@xxxxxxxxxxxxxxx> wrote:
> On 2/16/2016 9:08 AM, Corneliu ZUZU wrote:
>> This patch moves monitor_domctl to common-side.
>> Purpose: move what's common to common, prepare for implementation
>> of such vm-events on ARM.
>>
>> * move get_capabilities to arch-side => arch_monitor_get_capabilities.
>> * add arch-side monitor op handling function => arch_monitor_domctl_op.
>>    e.g. X86-side handles XEN_DOMCTL_MONITOR_OP_EMULATE_EACH_REP op
>> * add arch-side monitor event handling function => arch_monitor_domctl_event.
>>    e.g. X86-side handles XEN_DOMCTL_MONITOR_EVENT_MOV_TO_MSR event 
> enable/disable
>> * remove status_check
>>
>> Signed-off-by: Corneliu ZUZU <czuzu@xxxxxxxxxxxxxxx>
>>
>> ---
>> Changed since v3:
>>    * monitor_domctl @ common/monitor.c:
>>      - remove unused requested_status
>>      - sanity check mop->event range to avoid left-shift undefined behavior
> 
> Due to left-shift undefined behavior situations, shouldn't I also:
> 
> * in X86 arch_monitor_get_capabilities: replace '1 <<' w/ '1U <<'

There's no undefinedness there, since the right side operands of
<< are all constant. Using 1U here would be okay, but is not
strictly needed.

> * in X86 arch_monitor_domctl_event, 
> XEN_DOMCTL_MONITOR_EVENT_WRITE_CTRLREG case
> add a sanity check of mop->u.mov_to_cr.index before:
>      unsigned int ctrlreg_bitmask = 
> monitor_ctrlreg_bitmask(mop->u.mov_to_cr.index);
> , which basically translates to:
>      unsigned int ctrlreg_bitmask = (1U << mop->u.mov_to_cr.index);
> 
> ? (especially since mop->u.mov_to_cr.index is set by the caller).

Yes, there a range check would be needed, but preferably as a
separate patch (as this has nothing to do with the code motion
you perform here).

Jan


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