Re: [patch 21/32] NTB/msi: Convert to msi_on_each_desc()

[Thomas Gleixner]

On Thu, Dec 09 2021 at 16:58, Jason Gunthorpe wrote:
> On Thu, Dec 09, 2021 at 09:32:42PM +0100, Thomas Gleixner wrote:
>> That was my thought to avoid having different mechanisms.
>> 
>> The address/data pair is computed in two places:
>> 
>>   1) Activation of an interrupt
>>   2) Affinity setting on an interrupt
>> 
>> Both configure the IRTE when interrupt remapping is in place.
>> 
>> In both cases a vector is allocated in the vector domain and based on
>> the resulting target APIC / vector number pair the IRTE is
>> (re)configured.
>> 
>> So putting the hypercall into the vIRTE update is the obvious
>> place. Both activation and affinity setting can fail and propagate an
>> error code down to the originating caller.
>> 
>> Hmm?
>
> Okay, I think I get it. Would be nice to have someone from intel
> familiar with the vIOMMU protocols and qemu code remark what the
> hypervisor side can look like.
>
> There is a bit more work here, we'd have to change VFIO to somehow
> entirely disconnect the kernel IRQ logic from the MSI table and
> directly pass control of it to the guest after the hypervisor IOMMU IR
> secures it. ie directly mmap the msi-x table into the guest

That makes everything consistent and a clear cut on all levels, right?

Thanks,

        tglx