Re: [Qemu-devel] [PATCH v2] Add remove_boot_device_path() function for hot-unplug device

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 12, 2014 at 11:51:35PM +0800, Jun Li wrote:
> 
> On 05/11/2014 05:17 PM, Marcel Apfelbaum wrote:
> >On Sun, 2014-05-11 at 11:07 +0800, lijun wrote:
> >>On 04/22/2014 05:21 PM, Marcel Apfelbaum wrote:
> >>>On Wed, 2014-04-16 at 22:20 +0800, Jun Li wrote:
> >>>>Add remove_boot_device_path() function to remove bootindex when hot-unplug
> >>>>a device. This patch fixed virtio-blk/virtio-net/scsi-disk/scsi-generic device.
> >>>>So it has fixed bug1086603, ref:
> >>>>https://bugzilla.redhat.com/show_bug.cgi?id=1086603
> >>>>
> >>>>Make some changes based on Andreas's good suggestion.
> >>>>
> >>>>Signed-off-by: Jun Li <junmuzi@gmail.com>
> >>>>---
> >>>>   hw/block/virtio-blk.c   |  1 +
> >>>>   hw/net/virtio-net.c     |  1 +
> >>>>   hw/scsi/scsi-disk.c     |  6 ++++--
> >>>>   hw/scsi/scsi-generic.c  |  3 +++
> >>>>   include/sysemu/sysemu.h |  2 ++
> >>>>   vl.c                    | 16 ++++++++++++++++
> >>>>   6 files changed, 27 insertions(+), 2 deletions(-)
> >>>>
> >>>>diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
> >>>>index 8a568e5..ecdd266 100644
> >>>>--- a/hw/block/virtio-blk.c
> >>>>+++ b/hw/block/virtio-blk.c
> >>>>@@ -752,6 +752,7 @@ static void virtio_blk_device_unrealize(DeviceState *dev, Error **errp)
> >>>>       unregister_savevm(dev, "virtio-blk", s);
> >>>>       blockdev_mark_auto_del(s->bs);
> >>>>       virtio_cleanup(vdev);
> >>>>+    remove_boot_device_path(s->conf->bootindex, dev, "/disk@0,0");
> >>>>   }
> >>>>   static Property virtio_blk_properties[] = {
> >>>>diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> >>>>index 33bd233..520c029 100644
> >>>>--- a/hw/net/virtio-net.c
> >>>>+++ b/hw/net/virtio-net.c
> >>>>@@ -1633,6 +1633,7 @@ static void virtio_net_device_unrealize(DeviceState *dev, Error **errp)
> >>>>       g_free(n->vqs);
> >>>>       qemu_del_nic(n->nic);
> >>>>       virtio_cleanup(vdev);
> >>>>+    remove_boot_device_path(n->nic_conf.bootindex, dev, "/ethernet-phy@0");
> >>>>   }
> >>>>   static void virtio_net_instance_init(Object *obj)
> >>>>diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
> >>>>index 48a28ae..bb2176a 100644
> >>>>--- a/hw/scsi/scsi-disk.c
> >>>>+++ b/hw/scsi/scsi-disk.c
> >>>>@@ -2150,12 +2150,14 @@ static void scsi_disk_reset(DeviceState *dev)
> >>>>       s->tray_open = 0;
> >>>>   }
> >>>>-static void scsi_destroy(SCSIDevice *dev)
> >>>>+static void scsi_destroy(SCSIDevice *sdev)
> >>>>   {
> >>>>-    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, dev);
> >>>>+    SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, sdev);
> >>>>+    DeviceState *dev = DEVICE(sdev);
> >>>>       scsi_device_purge_requests(&s->qdev, SENSE_CODE(NO_SENSE));
> >>>>       blockdev_mark_auto_del(s->qdev.conf.bs);
> >>>>+    remove_boot_device_path(s->qdev.conf.bootindex, dev, NULL);
> >>>>   }
> >>>>   static void scsi_disk_resize_cb(void *opaque)
> >>>>diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
> >>>>index 8d92e0d..2531a44 100644
> >>>>--- a/hw/scsi/scsi-generic.c
> >>>>+++ b/hw/scsi/scsi-generic.c
> >>>>@@ -388,8 +388,11 @@ static void scsi_generic_reset(DeviceState *dev)
> >>>>   static void scsi_destroy(SCSIDevice *s)
> >>>>   {
> >>>>+    DeviceState *dev = DEVICE(s);
> >>>>+
> >>>>       scsi_device_purge_requests(s, SENSE_CODE(NO_SENSE));
> >>>>       blockdev_mark_auto_del(s->conf.bs);
> >>>>+    remove_boot_device_path(s->conf.bootindex, dev, NULL);
> >>>>   }
> >>>>   static int scsi_generic_initfn(SCSIDevice *s)
> >>>>diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> >>>>index ba5c7f8..f7ad1e2 100644
> >>>>--- a/include/sysemu/sysemu.h
> >>>>+++ b/include/sysemu/sysemu.h
> >>>>@@ -193,6 +193,8 @@ void rtc_change_mon_event(struct tm *tm);
> >>>>   void add_boot_device_path(int32_t bootindex, DeviceState *dev,
> >>>>                             const char *suffix);
> >>>>+void remove_boot_device_path(int32_t bootindex, DeviceState *dev,
> >>>>+                             const char *suffix);
> >>>>   char *get_boot_devices_list(size_t *size, bool ignore_suffixes);
> >>>>   DeviceState *get_boot_device(uint32_t position);
> >>>>diff --git a/vl.c b/vl.c
> >>>>index 9975e5a..1713c68 100644
> >>>>--- a/vl.c
> >>>>+++ b/vl.c
> >>>>@@ -1184,6 +1184,22 @@ void add_boot_device_path(int32_t bootindex, DeviceState *dev,
> >>>>       QTAILQ_INSERT_TAIL(&fw_boot_order, node, link);
> >>>>   }
> >>>>+void remove_boot_device_path(int32_t bootindex, DeviceState *dev,
> >>>>+                             const char *suffix)
> >>>>+{
> >>>>+    FWBootEntry *node, *next_node;
> >>>>+
> >>>>+    if (bootindex == -1) {
> >>>>+        return;
> >>>>+    }
> >>>>+
> >>>>+    QTAILQ_FOREACH_SAFE(node, &fw_boot_order, link, next_node)
> >>>>+        if (node->bootindex == bootindex) {
> >>>>+            QTAILQ_REMOVE(&fw_boot_order, node, link);
> >>>Hi Liu.
> >>>Sorry for the late response, but I was in vacation :) .
> >>>Your patch looks OK, I once wrote another one on the same issue
> >>>(it touched the same problem, but it was *completely* different).
> >>>
> >>>Here is the *real* problem: fw_boot_order list is not queried
> >>>again on guest reboot, so 'touching' the list has no effect.
> >>>While your code is correct (as far as I can tell), it seems
> >>>that his place is after the above problem is solved.
> >>>
> >>>No one is currently working on this, feel free
> >>>to take this challenge. I'll help however I can.
> >>Hi Marcel,
> >>
> >>Sorry, so later response. I got a heavy sick these days. I have see
> >>these discussion emails between you and Paolo.
> >>After guest reboot, seabios will got devices info from boards(this
> >>boards be generated by qemu command line). Just as Paolo's explanations,
> >>but I am not familiar with seabios. I will do some research about this.
> >>Thank you very much.
> >>
> >>BTW, My first name is Jun, my last name is Li, my English name is
> >>woodpecker, you could call me jun or woodpecker. :)
> >Hi Jun,
> >I hope you are feeling better!
> >If you need further assistance, just let us know.
> Hi Marcel,
> I just do a glancing debug, find that, when reboot guest, It will
> call function qemu_system_reset. So I want to add reset "fw_cfg" in
> function qemu_system_reset. Maybe this can fix your issue. But I
> have not try due to the limited time. This is just an ideal. As I am
> a sparetime "developer", so I can just fix this issue at weekend. So
> sorry.
> 
> Thanks,
> Jun Li

Well FW CFG changing across reboots will create all kind of problems.
So I think we should think about an alternative mechanism
if we want to make it all dynamic, a static boot index number is a
problematic api anyway, how do you prepare for ability to add more
devices at arbitrary places?  number everything 10,20,30, BASIC like?

For now your patch fixes a dangling pointer so I'll pick it up,
thanks!

-- 
MST