RE: [PATCH] iommu/hyper-v: Allow hyperv irq remapping without x2apic

[Michael Kelley (LINUX)]

From: Wei Liu <wei.liu@xxxxxxxxxx> Sent: Monday, November 14, 2022 5:59 AM
> 
> On Fri, Nov 11, 2022 at 02:53:59PM -0800, Nuno Das Neves wrote:
> > On 11/11/2022 9:58 AM, Michael Kelley (LINUX) wrote:
> > > From: Wei Liu <wei.liu@xxxxxxxxxx> Sent: Friday, November 11, 2022 9:27 AM
> [...]
> >
> > I've tested this patch on these Azure SKUs:
> > - Standard_D2S_v2 (intel xapic)
> > - Standard_D4ds_v4 (intel xapic)
> > - Standard_D4ds_v5 (intel x2apic)
> > - Standard_D4ads_v5 (amd xapic)
> >
> > I've tested with linux Dom0 (nested hyperv root partition) and as a
> > regular L1 guest.
> >
> 
> Okay. I think your tests are good.
> 
> Michael, do you have any further concern?
> 

If ms_hyperv_msi_ext_dest_id() returns "true", then
hyperv_prepare_irq_remapping() will still return -ENODEV and you
won't get interrupt remapping because it isn't needed, at least not
for guest VMs.  Is that what we want for the root partition?  Or does
ms_hyperv_msi_ext_dest_id() only return true in a guest partition,
and not in the root partition?  See commit d981059e13ff.

Michael