Re: [Xen-devel] [PATCH v2 1/2] x86/monitor: add masking support for write_ctrlreg events

[Tamas K Lengyel <tamas@xxxxxxxxxxxxx>]

On Fri, Jun 16, 2017 at 9:15 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 16.06.17 at 16:26, <tamas@xxxxxxxxxxxxx> wrote:
>> On Tue, May 30, 2017 at 3:46 AM, Petre Pircalabu
>> <ppircalabu@xxxxxxxxxxxxxxx> wrote:
>>> Add support for filtering out the write_ctrlreg monitor events if they
>>> are generated only by changing certains bits.
>>> A new parameter (bitmask) was added to the xc_monitor_write_ctrlreg
>>> function in order to mask the event generation if the changed bits are
>>> set.
>>>
>>> Signed-off-by: Petre Pircalabu <ppircalabu@xxxxxxxxxxxxxxx>
>>
>> Acked-by: Tamas K Lengyel <tamas@xxxxxxxxxxxxx>
>
> Are you btw in agreement with ...
>
>>> @@ -1107,6 +1107,11 @@ struct xen_domctl_monitor_op {
>>>              uint8_t sync;
>>>              /* Send event only on a change of value */
>>>              uint8_t onchangeonly;
>>> +            /*
>>> +             * Send event only if the changed bit in the control register
>>> +             * is not masked.
>>> +             */
>>> +            uint64_aligned_t bitmask;
>
> ... the 5-byte gap being introduced here, using of which won't
> be possible without bumping XEN_DOMCTL_INTERFACE_VERSION
> again? Generally we aim at making padding explicit and checking
> it to be zero on input / providing zero on output.

Yes, making the padding explicit would be better (but I'm not the
maintainer of the domctl interface so my ack doesn't cover that).

Tamas

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