Re: [PATCH RFC 00/22] EEH Support for VFIO PCI devices on PowerKVM guest

[Alex Williamson <alex.williamson@redhat.com>]

On Mon, 2014-05-05 at 13:56 +0200, Alexander Graf wrote:
> On 05/05/2014 03:27 AM, Gavin Shan wrote:
> > The series of patches intends to support EEH for PCI devices, which have been
> > passed through to PowerKVM based guest via VFIO. The implementation is
> > straightforward based on the issues or problems we have to resolve to support
> > EEH for PowerKVM based guest.
> >
> > - Emulation for EEH RTAS requests. Thanksfully, we already have infrastructure
> >    to emulate XICS. Without introducing new mechanism, we just extend that
> >    existing infrastructure to support EEH RTAS emulation. EEH RTAS requests
> >    initiated from guest are posted to host where the requests get handled or
> >    delivered to underly firmware for further handling. For that, the host kerenl
> >    has to maintain the PCI address (host domain/bus/slot/function to guest's
> >    PHB BUID/bus/slot/function) mapping via KVM VFIO device. The address mapping
> >    will be built when initializing VFIO device in QEMU and destroied when the
> >    VFIO device in QEMU is going to offline, or VM is destroy.
> 
> Do you also expose all those interfaces to user space? VFIO is as much 
> about user space device drivers as it is about device assignment.
> 
> I would like to first see an implementation that doesn't touch KVM 
> emulation code at all but instead routes everything through QEMU. As a 
> second step we can then accelerate performance critical paths inside of KVM.
> 
> That way we ensure that user space device drivers have all the power 
> over a device they need to drive it.

+1