From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53713) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gSIC0-0001mx-AB for qemu-devel@nongnu.org; Thu, 29 Nov 2018 04:01:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gSIBw-0002Uw-KQ for qemu-devel@nongnu.org; Thu, 29 Nov 2018 04:01:02 -0500 Date: Thu, 29 Nov 2018 10:00:46 +0100 From: Kevin Wolf Message-ID: <20181129090046.GA4797@linux.fritz.box> References: <20181121151211.15997-1-paul.durrant@citrix.com> <20181121151211.15997-15-paul.durrant@citrix.com> <20181128163447.GF4222@dhcp-200-186.str.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH 14/18] xen: add implementations of xen-qdisk connect and disconnect functions... List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paul Durrant Cc: "qemu-block@nongnu.org" , "qemu-devel@nongnu.org" , "xen-devel@lists.xenproject.org" , Stefano Stabellini , Anthony Perard , Max Reitz Am 28.11.2018 um 17:40 hat Paul Durrant geschrieben: > > -----Original Message----- > > From: Kevin Wolf [mailto:kwolf@redhat.com] > > Sent: 28 November 2018 16:35 > > To: Paul Durrant > > Cc: qemu-block@nongnu.org; qemu-devel@nongnu.org; xen- > > devel@lists.xenproject.org; Stefano Stabellini ; > > Anthony Perard ; Max Reitz > > Subject: Re: [PATCH 14/18] xen: add implementations of xen-qdisk connect > > and disconnect functions... > > > > Am 21.11.2018 um 16:12 hat Paul Durrant geschrieben: > > > ...and wire in the dataplane. > > > > > > This patch adds the remaining code to make the xen-qdisk XenDevice > > > functional. The parameters that a block frontend expects to find are > > > populated in the backend xenstore area, and the 'ring-ref' and > > > 'event-channel' values specified in the frontend xenstore area are > > > mapped/bound and used to set up the dataplane. > > > > > > Signed-off-by: Paul Durrant > > > --- > > > Cc: Stefano Stabellini > > > Cc: Anthony Perard > > > Cc: Kevin Wolf > > > Cc: Max Reitz > > > --- > > > hw/block/xen-qdisk.c | 140 > > +++++++++++++++++++++++++++++++++++++++++++++ > > > hw/xen/xen-bus.c | 12 ++-- > > > include/hw/xen/xen-bus.h | 8 +++ > > > include/hw/xen/xen-qdisk.h | 12 ++++ > > > 4 files changed, 166 insertions(+), 6 deletions(-) > > > > > > diff --git a/hw/block/xen-qdisk.c b/hw/block/xen-qdisk.c > > > index 35f7b70480..8c88393832 100644 > > > --- a/hw/block/xen-qdisk.c > > > +++ b/hw/block/xen-qdisk.c > > > @@ -9,6 +9,10 @@ > > > #include "qapi/visitor.h" > > > #include "hw/hw.h" > > > #include "hw/xen/xen-qdisk.h" > > > +#include "sysemu/blockdev.h" > > > +#include "sysemu/block-backend.h" > > > +#include "sysemu/iothread.h" > > > +#include "dataplane/xen-qdisk.h" > > > #include "trace.h" > > > > > > static char *xen_qdisk_get_name(XenDevice *xendev, Error **errp) > > > @@ -23,6 +27,11 @@ static void xen_qdisk_realize(XenDevice *xendev, > > Error **errp) > > > { > > > XenQdiskDevice *qdiskdev = XEN_QDISK_DEVICE(xendev); > > > XenQdiskVdev *vdev = &qdiskdev->vdev; > > > + BlockConf *conf = &qdiskdev->conf; > > > + DriveInfo *dinfo; > > > + bool is_cdrom; > > > + unsigned int info; > > > + int64_t size; > > > > > > if (!vdev->valid) { > > > error_setg(errp, "vdev property not set"); > > > @@ -30,13 +39,134 @@ static void xen_qdisk_realize(XenDevice *xendev, > > Error **errp) > > > } > > > > > > trace_xen_qdisk_realize(vdev->disk, vdev->partition); > > > + > > > + if (!conf->blk) { > > > + error_setg(errp, "drive property not set"); > > > + return; > > > + } > > > + > > > + if (!blk_is_inserted(conf->blk)) { > > > + error_setg(errp, "device needs media, but drive is empty"); > > > + return; > > > + } > > > > Hm, the code below suggests that you support CD-ROMs. Don't you want to > > support media change as well then? Which would mean that you need to > > support empty drives. > > Yes, that's a good point. I should get rid of that check. Or rather apply it only to hard disks. And for empty CDs, you'll probably need to create an empty BlockBackend (the !conf->blk case). Just check the IDE and/or SCSI code for comparison. > > > > > + if (!blkconf_apply_backend_options(conf, blk_is_read_only(conf- > > >blk), > > > + false, errp)) { > > > + return; > > > + } > > > + > > > + if (!blkconf_geometry(conf, NULL, 65535, 255, 255, errp)) { > > > + return; > > > + } > > > + > > > + dinfo = blk_legacy_dinfo(conf->blk); > > > + is_cdrom = (dinfo && dinfo->media_cd); > > > > It's called legacy for a reason. Don't use this in new devices. > > > > The proper way is to have two different devices for hard disks and CDs > > (like scsi-hd and scsi-cd). > > ...or presumably I could have a property? The legacy init code could > then set it based on the drive info. Technically yes, but why would that be a good way to model things? I mean, it's true that xen-qdisk is not real hardware, but I've never seen any hardware that has a switch to decide whether it should behave as a CD drive or a hard disk. Both have very different characteristics (read-only with removable media, or a single read-write disk), and the existing implementations use two separate devices. So even if you're not convinced that users will consider them different concepts (I am; and if they weren't different concepts, you wouldn't need an is_cdrom variable), consistency is still a good thing. Kevin