From 6b292920dbdd463bb80b82bef2063623a8e2da17 Mon Sep 17 00:00:00 2001 From: Sergio Lopez Pascual Date: Fri, 27 Sep 2019 11:46:41 +0100 Subject: [PATCH 2/2] virtio-blk: schedule virtio_notify_config to run on main context MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit RH-Author: Sergio Lopez Pascual Message-id: <20190927114641.20992-2-slp@redhat.com> Patchwork-id: 90907 O-Subject: [RHEL-AV-8.1.0 qemu-kvm PATCH 1/1] virtio-blk: schedule virtio_notify_config to run on main context Bugzilla: 1744955 RH-Acked-by: Eric Blake RH-Acked-by: Philippe Mathieu-Daudé RH-Acked-by: Max Reitz 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 . --Stefan] Signed-off-by: Sergio Lopez Reviewed-by: Kevin Wolf Message-id: 20190916112411.21636-1-slp@redhat.com Message-Id: <20190916112411.21636-1-slp@redhat.com> Signed-off-by: Stefan Hajnoczi (cherry picked from commit f9a7e3698a737ee75a7b0af34203303df982550f) Signed-off-by: Sergio Lopez Signed-off-by: Danilo C. L. de Paula --- 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 cbb3729..0d9adcd 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 = { -- 1.8.3.1