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

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Message-ID: <30741787-441a-034f-f8d4-9f1060841051@linux.ibm.com>
Date:   Wed, 31 May 2023 10:51:54 -0400
From:   Matthew Rosato <mjrosato@...ux.ibm.com>
To:     Tony Krowiak <akrowiak@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        alex.williamson@...hat.com, Heiko Carstens <hca@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        "agordeev@...ux.ibm.com" <agordeev@...ux.ibm.com>
Cc:     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 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.