linux-kernel - Re: [PATCH v1] s390/vfio-ap: Signal eventfd when guest AP configuration is changed

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Message-ID: <d1b36877-14ea-4110-84c1-941defc8d3a2@linux.ibm.com>
Date: Thu, 16 Jan 2025 11:46:02 -0500
From: Anthony Krowiak <akrowiak@...ux.ibm.com>
To: freude@...ux.ibm.com, Rorie Reyes <rreyes@...ux.ibm.com>
Cc: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, hca@...ux.ibm.com, borntraeger@...ibm.com,
        agordeev@...ux.ibm.com, gor@...ux.ibm.com, pasic@...ux.ibm.com,
        jjherne@...ux.ibm.com, alex.williamson@...hat.com
Subject: Re: [PATCH v1] s390/vfio-ap: Signal eventfd when guest AP
 configuration is changed

>
> Rorie, this is to inform listeners on the host of the guest.
> The guest itself already sees this "inside" with uevents triggered
> by the AP bus code.
>
> Do you have a consumer for these events?

There is a series of QEMU patches that register a notification handler 
for this
event. When that handler gets called, it generates and queues a CRW to 
the guest
indicating there is event information pending which will cause the AP 
bus driver
to get notified of the AP configuration change via its ap_bus_cfg_chg 
notifier call.

The QEMU series can be seen at:
https://lore.kernel.org/qemu-devel/7171c479-5cb4-4748-ba37-da4cf2fac35b@linux.ibm.com/T/ 


Kind regards,
A Krowiak