linux-kernel - Re: [PATCH 2/2] vfio/mdev: don't warn if ->request is not set

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Message-ID: <20210726172831.3a7978fd.alex.williamson@redhat.com>
Date:   Mon, 26 Jul 2021 17:28:31 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     Cornelia Huck <cohuck@...hat.com>, Christoph Hellwig <hch@....de>,
        Kirti Wankhede <kwankhede@...dia.com>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] vfio/mdev: don't warn if ->request is not set

On Mon, 26 Jul 2021 20:09:06 -0300
Jason Gunthorpe <jgg@...dia.com> wrote:

> On Mon, Jul 26, 2021 at 07:07:04PM +0200, Cornelia Huck wrote:
> 
> > But I wonder why nobody else implements this? Lack of surprise removal?  
> 
> The only implementation triggers an eventfd that seems to be the same
> eventfd as the interrupt..
> 
> Do you know how this works in userspace? I'm surprised that the
> interrupt eventfd can trigger an observation that the kernel driver
> wants to be unplugged?

I think we're talking about ccw, but I see QEMU registering separate
eventfds for each of the 3 IRQ indexes and the mdev driver specifically
triggering the req_trigger...?  Thanks,

Alex