Re: [PATCH 0/3] vfio-ccw: support hsch/csch (kernel part)

Cornelia Huck
2018-11-26T19:00:51Z

On Mon, 26 Nov 2018 13:57:06 -0500
Farhan Ali <alifm@linux.ibm.com> wrote:

> On 11/22/2018 11:54 AM, Cornelia Huck wrote:
> > [This is the Linux kernel part, git tree is available at
> > https://git.kernel.org/pub/scm/linux/kernel/git/kvms390/vfio-ccw.git vfio-ccw-caps
> >
> > The companion QEMU patches are available at
> > https://github.com/cohuck/qemu vfio-ccw-caps]
> >
> > Currently, vfio-ccw only relays START SUBCHANNEL requests to the real
> > device. This tends to work well for the most common 'good path' scenarios;
> > however, as we emulate {HALT,CLEAR} SUBCHANNEL in QEMU, things like
> > clearing pending requests at the device is currently not supported.
> > This may be a problem for e.g. error recovery.
> >
> > This patch series introduces capabilities (similar to what vfio-pci uses)
> > and exposes a new async region for handling hsch/csch.
> >
> > Very lightly tested (I can interact with a dasd as before; I have not
> > found a reliable way to trigger hsch/csch in the Linux dasd guest driver.)
> >
>
> I was able to trigger the guest DASD driver to issue a csch instruction,
> and from my brief testing it seems to be working just like it would on
> the LPAR. (I basically tested with 2 threads trying to issue DASD device
> reserve and release ioctls, on the same DASD device, in a busy loop).
>
> I am going to spend some time doing a deeper review.

Cool, thanks a lot!