From ed8f16b1786f28d3fb6c6cef79cd4f94deae8857 Mon Sep 17 00:00:00 2001

From: Sergio Lopez Pascual <slp@redhat.com>

Date: Thu, 28 Nov 2019 11:30:47 +0100

Subject: [PATCH] virtio-scsi: fixed virtio_scsi_ctx_check failed when

 detaching scsi disk

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RH-Author: Sergio Lopez Pascual <slp@redhat.com>

Message-id: <20191128113047.253669-2-slp@redhat.com>

Patchwork-id: 92747

O-Subject: [RHEL-7.8 qemu-kvm-rhev PATCH v2 1/1] virtio-scsi: fixed virtio_scsi_ctx_check failed when detaching scsi disk

Bugzilla: 1764120

RH-Acked-by: Markus Armbruster <armbru@redhat.com>

RH-Acked-by: Max Reitz <mreitz@redhat.com>

RH-Acked-by: Maxim Levitsky <mlevitsk@redhat.com>

From: Zhengui li <lizhengui@huawei.com>

commit a6f230c move blockbackend back to main AioContext on unplug. It set the AioContext of

SCSIDevice to the main AioContex, but s->ctx is still the iothread AioContex（if the scsi controller

is configure with iothread）. So if there are having in-flight requests during unplug, a failing assertion

happend. The bt is below:

(gdb) bt

#0  0x0000ffff86aacbd0 in raise () from /lib64/libc.so.6

#1  0x0000ffff86aadf7c in abort () from /lib64/libc.so.6

#2  0x0000ffff86aa6124 in __assert_fail_base () from /lib64/libc.so.6

#3  0x0000ffff86aa61a4 in __assert_fail () from /lib64/libc.so.6

#4  0x0000000000529118 in virtio_scsi_ctx_check (d=<optimized out>, s=<optimized out>, s=<optimized out>) at /home/qemu-4.0.0/hw/scsi/virtio-scsi.c:246

#5  0x0000000000529ec4 in virtio_scsi_handle_cmd_req_prepare (s=0x2779ec00, req=0xffff740397d0) at /home/qemu-4.0.0/hw/scsi/virtio-scsi.c:559

#6  0x000000000052a228 in virtio_scsi_handle_cmd_vq (s=0x2779ec00, vq=0xffff7c6d7110) at /home/qemu-4.0.0/hw/scsi/virtio-scsi.c:603

#7  0x000000000052afa8 in virtio_scsi_data_plane_handle_cmd (vdev=<optimized out>, vq=0xffff7c6d7110) at /home/qemu-4.0.0/hw/scsi/virtio-scsi-dataplane.c:59

#8  0x000000000054d94c in virtio_queue_host_notifier_aio_poll (opaque=<optimized out>) at /home/qemu-4.0.0/hw/virtio/virtio.c:2452

assert(blk_get_aio_context(d->conf.blk) == s->ctx) failed.

To avoid assertion failed,  moving the "if" after qdev_simple_device_unplug_cb.

In addition, to avoid another qemu crash below, add aio_disable_external before

qdev_simple_device_unplug_cb, which disable the further processing of external clients

when doing qdev_simple_device_unplug_cb.

(gdb) bt

#0  scsi_req_unref (req=0xffff6802c6f0) at hw/scsi/scsi-bus.c:1283

#1  0x00000000005294a4 in virtio_scsi_handle_cmd_req_submit (req=<optimized out>,

    s=<optimized out>) at /home/qemu-4.0.0/hw/scsi/virtio-scsi.c:589

#2  0x000000000052a2a8 in virtio_scsi_handle_cmd_vq (s=s@entry=0x9c90e90,

    vq=vq@entry=0xffff7c05f110) at /home/qemu-4.0.0/hw/scsi/virtio-scsi.c:625

#3  0x000000000052afd8 in virtio_scsi_data_plane_handle_cmd (vdev=<optimized out>,

    vq=0xffff7c05f110) at /home/qemu-4.0.0/hw/scsi/virtio-scsi-dataplane.c:60

#4  0x000000000054d97c in virtio_queue_host_notifier_aio_poll (opaque=<optimized out>)

    at /home/qemu-4.0.0/hw/virtio/virtio.c:2447

#5  0x00000000009b204c in run_poll_handlers_once (ctx=ctx@entry=0x6efea40,

    timeout=timeout@entry=0xffff7d7f7308) at util/aio-posix.c:521

#6  0x00000000009b2b64 in run_poll_handlers (ctx=ctx@entry=0x6efea40,

    max_ns=max_ns@entry=4000, timeout=timeout@entry=0xffff7d7f7308) at util/aio-posix.c:559

#7  0x00000000009b2ca0 in try_poll_mode (ctx=ctx@entry=0x6efea40, timeout=0xffff7d7f7308,

    timeout@entry=0xffff7d7f7348) at util/aio-posix.c:594

#8  0x00000000009b31b8 in aio_poll (ctx=0x6efea40, blocking=blocking@entry=true)

    at util/aio-posix.c:636

#9  0x00000000006973cc in iothread_run (opaque=0x6ebd800) at iothread.c:75

#10 0x00000000009b592c in qemu_thread_start (args=0x6efef60) at util/qemu-thread-posix.c:502

#11 0x0000ffff8057f8bc in start_thread () from /lib64/libpthread.so.0

#12 0x0000ffff804e5f8c in thread_start () from /lib64/libc.so.6

(gdb) p bus

$1 = (SCSIBus *) 0x0

Signed-off-by: Zhengui li <lizhengui@huawei.com>

Message-Id: <1563696502-7972-1-git-send-email-lizhengui@huawei.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Message-Id: <1563829520-17525-1-git-send-email-pbonzini@redhat.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

(cherry picked from commit 9c5aad84da1c37429d06c193f23a8df6445ed29e)

[slp: we need to get a reference to the underlying BDS to be able

to switch the context after calling qdev_simple_device_unplug_cb(),

as in 2.12 this causes the SCSIDevice to go away immediately]

Signed-off-by: Sergio Lopez <slp@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 hw/scsi/virtio-scsi.c | 30 ++++++++++++++++++++++++++----

 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c

index 391500b..2bd54b3 100644

--- a/hw/scsi/virtio-scsi.c

+++ b/hw/scsi/virtio-scsi.c

@@ -20,6 +20,7 @@

 #include "qemu/error-report.h"

 #include "qemu/iov.h"

 #include "sysemu/block-backend.h"

+#include "sysemu/blockdev.h"

 #include "hw/scsi/scsi.h"

 #include "scsi/constants.h"

 #include "hw/virtio/virtio-bus.h"

@@ -839,6 +840,9 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev,

     VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);

     VirtIOSCSI *s = VIRTIO_SCSI(vdev);

     SCSIDevice *sd = SCSI_DEVICE(dev);

+    AioContext *ctx = s->ctx ?: qemu_get_aio_context();

+    BlockDriverState *bs;

+    DriveInfo *dinfo;

     if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {

         virtio_scsi_acquire(s);

@@ -848,13 +852,31 @@ static void virtio_scsi_hotunplug(HotplugHandler *hotplug_dev, DeviceState *dev,

         virtio_scsi_release(s);

     }

-    if (s->ctx) {

+    /*

+     * This SCSIDevice goes away after calling qdev_simple_device_unplug_cb(),

+     * so get a reference to the underlying BDS here to be able to switch

+     * its AioContext afterwards.

+     */

+    bs = blk_bs(sd->conf.blk);

+

+    /*

+     * Drives attached to a legacy device will get auto deleted while

+     * unplugging the latter, so we don't need to switch their context.

+     * Get a reference to dinfo here, which is only NULL for non-legacy

+     * devices, and use it to avoid doing the switch for drives attached

+     * to legacy devices.

+     */

+    dinfo = blk_legacy_dinfo(sd->conf.blk);

+

+    aio_disable_external(ctx);

+    qdev_simple_device_unplug_cb(hotplug_dev, dev, errp);

+    aio_enable_external(ctx);

+

+    if (s->ctx && bs && !dinfo) {

         virtio_scsi_acquire(s);

-        blk_set_aio_context(sd->conf.blk, qemu_get_aio_context());

+        bdrv_set_aio_context(bs, qemu_get_aio_context());

         virtio_scsi_release(s);

     }

-

-    qdev_simple_device_unplug_cb(hotplug_dev, dev, errp);

 }

 static struct SCSIBusInfo virtio_scsi_scsi_info = {

-- 

1.8.3.1