>>> On 31.03.17 at 01:01, <chao....@intel.com> wrote:
> On Fri, Mar 31, 2017 at 01:46:33PM +0800, Tian, Kevin wrote:
>>> From: Gao, Chao
>>> Sent: Wednesday, March 29, 2017 1:12 PM
>>> --- a/xen/drivers/passthrough/io.c
>>> +++ b/xen/drivers/passthrough/io.c
>>> @@ -618,6 +618,8 @@ int pt_irq_destroy_bind(
>>> else
>>> what = "bogus";
>>> }
>>> + else if ( iommu_intpost && pirq && pirq_dpci->gmsi.posted )
>>
>>No need to check iommu_intpost. Just keep later conditions.
>
> ok. Is it for if posted is set, the iommu_intpost should be true?
>
>>
>>btw isn't the condition be " (pirq_dpci && pirq_dpci->gmsi.posted)"?
>
> I don't think so. pirq, not pirq_dpci, is consumed by pi_update_irte.
> Furthermore if pirq_dpci is null, pirq is also null. But it is not true
> in turn.
With
pirq_dpci = pirq_dpci(pirq);
it _is_ the other way around, which can then also be expressed
as "if pirq_dpci is non-NULL, pirq is non-NULL too", which is the
precondition you need to consume (dereference) pirq. There is
a reason other code around here also only ever checks pirq_dpci
(even when using pirq).
Jan
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