Re: [Xen-devel] PV guest with PCI passthrough crash on Xen 4.8.3 inside KVM when booted through OVMF

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Fri, Feb 16, 2018 at 04:35:14PM -0500, Rich Persaud wrote:
> On Feb 16, 2018, at 14:02, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
> > 
> > IMO, PCI Passthrough is a trainwreck, and it is a miracle it functions
> > at all.
> 
> Would that statement apply to other hypervisors like KVM, VMware ESX or 
> Hyper-V, i.e. are the deficiencies in PCI devices/firmware, IOMMUs, platform 
> firmware?  
> 
> If the statement is Xen specific, are there specific issues or known sections 
> of Xen code that would benefit from a rewrite or redesign inspired by other 
> hypervisors?

I personally don't fancy the fact that MSI-X handling for pass-through
to HVM guests is split between QEMU and the hypervisor itself. It
makes tracking down bugs or just trying to figure out the code flow
quite complex IMO.

I have plans to switch HVM to use the pass-through code being added
for PVH:

https://lists.xenproject.org/archives/html/xen-devel/2018-01/msg02042.html

But that's still quite far away from being usable by unprivileged
guests.

Roger.

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