From: Halil Pasic <pasic@linux.ibm.com>
To: Cornelia Huck <cohuck@redhat.com>
Cc: Jared Rossi <jrossi@linux.ibm.com>,
Eric Farman <farman@linux.ibm.com>,
linux-s390@vger.kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] vfio-ccw: Enable transparent CCW IPL from DASD
Date: Fri, 24 Apr 2020 15:02:40 +0200 [thread overview]
Message-ID: <20200424150240.6fdede81.pasic@linux.ibm.com> (raw)
In-Reply-To: <20200420141317.4537498f.cohuck@redhat.com>
On Mon, 20 Apr 2020 14:13:17 +0200
Cornelia Huck <cohuck@redhat.com> wrote:
> > Remove the explicit prefetch check when using vfio-ccw devices.
> > This check is not needed as all Linux channel programs are intended
> > to use prefetch and will be executed in the same way regardless.
>
> Hm... my understanding is that we have the reasonable expectation that
> our guests will always issue channel programs that work fine with
> prefetch even if the bit is not set in the orb (including CCW IPL, in
> the way it is implemented in the s390-ccw QEMU bios), and therefore
> this patch is just making things less complicated.
AFAIR the problem is not s390-ccw QEMU bios. We could easily fix that.
The practical problem is some channel programs generated by zipl that
simply fail to set the bit (although they could). That is a perfectly
legit thing to do, because the prefetch bit was originally about
performance.
Sorry I missed your mail, so complained about the same
issues.
Regards,
Halil
next prev parent reply other threads:[~2020-04-24 13:03 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-17 18:29 [PATCH 0/1] vfio-ccw: Enable transparent CCW IPL from DASD Jared Rossi
2020-04-17 18:29 ` [PATCH 1/1] " Jared Rossi
2020-04-20 12:13 ` Cornelia Huck
2020-04-24 13:02 ` Halil Pasic [this message]
2020-04-23 13:56 ` Halil Pasic
2020-04-23 15:11 ` Cornelia Huck
2020-04-23 20:25 ` Eric Farman
2020-04-24 12:50 ` Halil Pasic
2020-04-29 0:38 ` Jared Rossi
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