[pve-devel] [PATCH qemu] fix #2486: include fix for disk hot-resize regression (w/ iothread=1)

[Stefan Reiter]

See: https://lists.nongnu.org/archive/html/qemu-devel/2019-09/msg03201.html

Signed-off-by: Stefan Reiter <s.reiter at proxmox.com>
---
 ...ule-virtio_notify_config-to-run-on-m.patch | 76 +++++++++++++++++++
 debian/patches/series                         |  1 +
 2 files changed, 77 insertions(+)
 create mode 100644 debian/patches/extra/0002-virtio-blk-schedule-virtio_notify_config-to-run-on-m.patch

diff --git a/debian/patches/extra/0002-virtio-blk-schedule-virtio_notify_config-to-run-on-m.patch b/debian/patches/extra/0002-virtio-blk-schedule-virtio_notify_config-to-run-on-m.patch
new file mode 100644
index 0000000..f20c7d7
--- /dev/null
+++ b/debian/patches/extra/0002-virtio-blk-schedule-virtio_notify_config-to-run-on-m.patch
@@ -0,0 +1,76 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Sergio Lopez <slp at redhat.com>
+Date: Mon, 16 Sep 2019 13:24:12 +0200
+Subject: [PATCH] virtio-blk: schedule virtio_notify_config to run on main
+ context
+
+virtio_notify_config() needs to acquire the global mutex, which isn't
+allowed from an iothread, and may lead to a deadlock like this:
+
+ - main thead
+  * Has acquired: qemu_global_mutex.
+  * Is trying the acquire: iothread AioContext lock via
+    AIO_WAIT_WHILE (after aio_poll).
+
+ - iothread
+  * Has acquired: AioContext lock.
+  * Is trying to acquire: qemu_global_mutex (via
+    virtio_notify_config->prepare_mmio_access).
+
+If virtio_blk_resize() is called from an iothread, schedule
+virtio_notify_config() to be run in the main context BH.
+
+[Removed unnecessary newline as suggested by Kevin Wolf
+<kwolf at redhat.com>.
+--Stefan]
+
+Signed-off-by: Sergio Lopez <slp at redhat.com>
+Reviewed-by: Kevin Wolf <kwolf at redhat.com>
+Message-id: 20190916112411.21636-1-slp at redhat.com
+Message-Id: <20190916112411.21636-1-slp at redhat.com>
+Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
+---
+ hw/block/virtio-blk.c | 16 +++++++++++++++-
+ 1 file changed, 15 insertions(+), 1 deletion(-)
+
+diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
+index cbb3729158..0d9adcdaff 100644
+--- a/hw/block/virtio-blk.c
++++ b/hw/block/virtio-blk.c
+@@ -16,6 +16,7 @@
+ #include "qemu/iov.h"
+ #include "qemu/module.h"
+ #include "qemu/error-report.h"
++#include "qemu/main-loop.h"
+ #include "trace.h"
+ #include "hw/block/block.h"
+ #include "sysemu/blockdev.h"
+@@ -1082,11 +1083,24 @@ static int virtio_blk_load_device(VirtIODevice *vdev, QEMUFile *f,
+     return 0;
+ }
+ 
++static void virtio_resize_cb(void *opaque)
++{
++    VirtIODevice *vdev = opaque;
++
++    assert(qemu_get_current_aio_context() == qemu_get_aio_context());
++    virtio_notify_config(vdev);
++}
++
+ static void virtio_blk_resize(void *opaque)
+ {
+     VirtIODevice *vdev = VIRTIO_DEVICE(opaque);
+ 
+-    virtio_notify_config(vdev);
++    /*
++     * virtio_notify_config() needs to acquire the global mutex,
++     * so it can't be called from an iothread. Instead, schedule
++     * it to be run in the main context BH.
++     */
++    aio_bh_schedule_oneshot(qemu_get_aio_context(), virtio_resize_cb, vdev);
+ }
+ 
+ static const BlockDevOps virtio_block_ops = {
+-- 
+2.20.1
+
diff --git a/debian/patches/series b/debian/patches/series
index a2c1271..a09ba1b 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -1,4 +1,5 @@
 extra/0001-monitor-qmp-resume-monitor-when-clearing-its-queue.patch
+extra/0002-virtio-blk-schedule-virtio_notify_config-to-run-on-m.patch
 pve/0001-PVE-Config-block-file-change-locking-default-to-off.patch
 pve/0002-PVE-Config-Adjust-network-script-path-to-etc-kvm.patch
 pve/0003-PVE-Config-set-the-CPU-model-to-kvm64-32-instead-of-.patch
-- 
2.20.1