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Mon, 20 Apr 2020 12:29:21 +0000 (UTC) Received: from gondolin (ovpn-112-224.ams2.redhat.com [10.36.112.224]) by smtp.corp.redhat.com (Postfix) with ESMTP id 278675DA82; Mon, 20 Apr 2020 12:29:19 +0000 (UTC) Date: Mon, 20 Apr 2020 14:29:17 +0200 From: Cornelia Huck To: Jared Rossi Subject: Re: [PATCH 1/1] vfio-ccw: Enable transparent CCW IPL from DASD Message-ID: <20200420142917.206d36a5.cohuck@redhat.com> In-Reply-To: <20200420142617.5e255265.cohuck@redhat.com> References: <20200417183838.11796-1-jrossi@linux.ibm.com> <20200417183838.11796-2-jrossi@linux.ibm.com> <20200420142617.5e255265.cohuck@redhat.com> Organization: Red Hat GmbH MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=205.139.110.120; envelope-from=cohuck@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs1p.gnu.org: First seen = 2020/04/20 04:32:42 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eric Farman , qemu-s390x@nongnu.org, qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Mon, 20 Apr 2020 14:26:17 +0200 Cornelia Huck wrote: > On Fri, 17 Apr 2020 14:38:38 -0400 > Jared Rossi 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. > > As already commented on the Linux patch: Can we log something, so this > is debuggable if this statement does not hold true in the future? > > > > > Signed-off-by: Jared Rossi > > --- > > hw/vfio/ccw.c | 13 +++---------- > > 1 file changed, 3 insertions(+), 10 deletions(-) > > > > diff --git a/hw/vfio/ccw.c b/hw/vfio/ccw.c > > index 50cc2ec75c..e649377b68 100644 > > --- a/hw/vfio/ccw.c > > +++ b/hw/vfio/ccw.c > > @@ -74,16 +74,9 @@ static IOInstEnding vfio_ccw_handle_request(SubchDev *sch) > > struct ccw_io_region *region = vcdev->io_region; > > int ret; > > > > - if (!(sch->orb.ctrl0 & ORB_CTRL0_MASK_PFCH)) { > > - if (!(vcdev->force_orb_pfch)) { > > - warn_once_pfch(vcdev, sch, "requires PFCH flag set"); > > - sch_gen_unit_exception(sch); > > - css_inject_io_interrupt(sch); > > - return IOINST_CC_EXPECTED; > > - } else { > > - sch->orb.ctrl0 |= ORB_CTRL0_MASK_PFCH; > > - warn_once_pfch(vcdev, sch, "PFCH flag forced"); > > - } > > + if (!(sch->orb.ctrl0 & ORB_CTRL0_MASK_PFCH) && vcdev->force_orb_pfch) { > > + sch->orb.ctrl0 |= ORB_CTRL0_MASK_PFCH; > > + warn_once_pfch(vcdev, sch, "PFCH flag forced"); > > } > > What happens when you run it with an old kernel? I guess the I/O is > only rejected later (after a trip into the kernel), but has that path > ever been tested? > > > > > QEMU_BUILD_BUG_ON(sizeof(region->orb_area) != sizeof(ORB)); > Oh, and do we want to deprecate the force prefetch interface in the future? We probably need to wait a bit, until the kernel changes have become widely available.