Re: [Xen-devel] [PATCH v3 2/6] VMX: Properly handle pi when all the assigned devices are removed

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.09.16 at 11:22, <feng.wu@xxxxxxxxx> wrote:
>> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>> Sent: Thursday, September 1, 2016 4:21 PM
>> >>> On 31.08.16 at 05:56, <feng.wu@xxxxxxxxx> wrote:
>> > This patch handles some concern cases when the last assigned device
>> > is removed from the domain. In this case we should carefully handle
>> > pi descriptor and the per-cpu blocking list, to make sure:
>> > - all the PI descriptor are in the right state when next time a
>> > devices is assigned to the domain again.
>> > - No remaining vcpus of the domain in the per-cpu blocking list.
>> >
>> > Basically, we pause the domain before zapping the PI hooks and
>> > removing the vCPU from the blocking list, then unpause it after
>> > that.
>> >
>> > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
>> 
>> Looks plausible, but
>> a) as already for patch 1 I'm missing information on what changed
>>    since v2 and
> 
> The biggest changes since v2 is that we use domain pause/unpause
> (suggested by George) to handle the concern case, while v2 was using
> some ugly and tricky method to do it, which was considered as hard
> to maintain.
> 
>> b) doesn't this make unnecessary patch 1?
> 
> The purpose of patch 1 is to make sure the two hooks are installed
> while CPU side PI is available event VT-d PI is not supported, I cannot
> see why this patch will make it unnecessary.

So I guess this doesn't hold anymore with your subsequent reply
to my comments on patch 1?

Jan


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