Re: [Xen-devel] [PATCH v12 1/7] passthrough: don't migrate pirq when it is delivered through VT-d PI

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 07.04.17 at 09:23, <chao.gao@xxxxxxxxx> wrote:
> On Fri, Apr 07, 2017 at 05:50:36AM -0600, Jan Beulich wrote:
>>>>> On 07.04.17 at 06:07, <chao.gao@xxxxxxxxx> wrote:
>>> Cc: kevin
>>> 
>>> On Fri, Apr 07, 2017 at 04:38:00AM -0600, Jan Beulich wrote:
>>>>>>> On 06.04.17 at 02:30, <chao.gao@xxxxxxxxx> wrote:
>>>>> --- a/xen/arch/x86/hvm/hvm.c
>>>>> +++ b/xen/arch/x86/hvm/hvm.c
>>>>> @@ -438,6 +438,9 @@ static int hvm_migrate_pirq(struct domain *d, struct 
>>> hvm_pirq_dpci *pirq_dpci,
>>>>>      struct vcpu *v = arg;
>>>>>  
>>>>>      if ( (pirq_dpci->flags & HVM_IRQ_DPCI_MACH_MSI) &&
>>>>> +         (pirq_dpci->flags & HVM_IRQ_DPCI_GUEST_MSI) &&
>>>>> +         /* Needn't migrate pirq if this pirq is delivered to guest 
>>> directly.*/
>>>>> +         (!pirq_dpci->gmsi.posted) &&
>>>>>           (pirq_dpci->gmsi.dest_vcpu_id == v->vcpu_id) )
>>>>>      {
>>>>
>>>>I don't think I've seen you address Kevin's comment on this for v11,
>>>>and like Kevin I can't immediately see why the above addition would
>>>>be correct. Do you perhaps mean
>>>>
>>>>    if ( (pirq_dpci->flags & HVM_IRQ_DPCI_MACH_MSI) &&
>>>>         /* Needn't migrate pirq if this pirq is delivered to guest 
> directly.*/
>>>>         (!pirq_dpci->gmsi.posted ||
>>>>          <whatever is appropriate here, if anything>) &&
>>>>         (pirq_dpci->gmsi.dest_vcpu_id == v->vcpu_id) )
>>> 
>>> Sorry to Kevin. And thanks to point it out. 
>>> But I thought we had discussed this in 
>>> https://lists.xenproject.org/archives/html/xen-devel/2017-03/msg04383.html. 
>>> I 
>>> did think you agreed with me.
>>> gmsi is invalid when pirq_dpci is not GUEST_MSI, is there something I have
>>> ignored?
>>
>>You've been talking about GUEST_PCI there, which I did (and do)
>>agree we can't handle here. So for the purposes of your series,
>>simply adding the gmsi.posted check would be the right thing imo.
>>I don't think I see anything wrong with the ->gmsi accesses here:
>>The GUEST_PCI code simply doesn't set them, so dest_vcpu_id
>>will still be -1 (from pt_pirq_init()). So I don't see any bug being
>>fixed here with the extra other check you add. If you agree, I
>>can take that line and the commit message sentence out while
>>committing.
> 
> Ok. I admit I said it's bug is wrong. feel free to do what you want.

Well, looks like I forgot to adjust the commit message.
-ETOOMUCHSTUFFGOINGONTODAY.

Jan


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