Re: [Xen-devel] [PATCH v11 1/6] passthrough: don't migrate pirq when it is delivered through VT-d PI

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.03.17 at 01:10, <chao.gao@xxxxxxxxx> wrote:
> On Fri, Mar 31, 2017 at 01:28:02PM +0800, Tian, Kevin wrote:
>>> From: Chao Gao
>>> Sent: Wednesday, March 29, 2017 1:12 PM
>>> --- 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) )
>>
>>simply looking at above change it's more than what you intend to change.
>>Previously even w/o GUEST_MSI flag will fall into that path, but now
>>you limit it to only GUEST_MSI and irq remapping (i.e. changed the
>>behavior for both posted case and w/o GUEST_MSI case). I haven't looked
>>whether MACH_MASI always set with GUEST_MSI, but my gut-feeling 
>>looks not correct here.
> 
> Yes. It's a problem. I think the original code may be wrong for it acquires
> gmsi.dest_vcpu_id without checking 'flags' of pirq_dpci. Do we need to migrate
> pirq when its type is GUEST_PCI?

It probably would be nice, but we don't know where to migrate it to:
The names in "pirq_dpci->gmsi.dest_vcpu_id" should make this pretty
clear, I would think.

Jan


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