linux-kernel - Re: [PATCH 0/3] s390/vfio-ap: fix hang when mdev attached to guest is removed

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Date:   Thu, 1 Jun 2023 14:47:22 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Matthew Rosato <mjrosato@...ux.ibm.com>
Cc:     Tony Krowiak <akrowiak@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        "agordeev@...ux.ibm.com" <agordeev@...ux.ibm.com>,
        jjherne@...ux.ibm.com, pasic@...ux.ibm.com, farman@...ux.ibm.com,
        borntraeger@...ux.ibm.com, Cedric Le Goater <clegoate@...hat.com>
Subject: Re: [PATCH 0/3] s390/vfio-ap: fix hang when mdev attached to guest
 is removed

On Wed, 31 May 2023 10:51:54 -0400
Matthew Rosato <mjrosato@...ux.ibm.com> wrote:

> On 5/30/23 6:35 PM, Tony Krowiak wrote:
> > When a user attempts to remove a vfio-ap mediated device attached to a
> > guest, the operation hangs until the mdev's fd is closed by the guest
> > (i.e., the hostdev is detached or the guest is shut down). This patch 
> > series provides kernel-side code that allows userspace to set up a 
> > communication channel that will allow the vfio_ap device driver to notify 
> > userspace when a request to release the mdev is received, so that userspace
> > can close the mdev fd and avoid the hang. The patch series provides the 
> > following:  
> > 
> > 1. Introduces code to handle the VFIO_DEVICE_GET_IRQ_INFO and 
> >    VFIO_DEVICE_SET_IRQS ioctl calls to set the eventfd_ctx for signaling a
> >    device request to userspace. 
> > 
> > 2. Wires up the VFIO bus driver callback to request a release of the mdev.
> >    When invoked, the vfio_ap device driver will use the eventfd_ctx set up
> >    in #1 to signal a request to userspace to release the mdev.
> >   
> 
> As to how this series eventually reaches master...  It touches both s390 and vfio.  
> 
> @Alex/@...0 maintainers -- I suggest it go through s390 given the
> diffstat, it's almost completely in s390 drivers code.  However there
> is a uapi hit to vfio.h (in patch 1) that should get at least an ACK
> from Alex beforehand.

Ack'd, I'll expect this to go through the s390 tree.  Thanks,

Alex