* [Qemu-devel] [PATCH v2 0/2] virtio-scsi: fix hotplug ->reset() vs event race
@ 2018-07-16 8:37 Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 1/2] qdev: add HotplugHandler->post_plug() callback Stefan Hajnoczi
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: Stefan Hajnoczi @ 2018-07-16 8:37 UTC (permalink / raw)
To: qemu-devel
Cc: l00284672, Igor Mammedov, Fam Zheng, Michael S. Tsirkin,
Paolo Bonzini, Stefan Hajnoczi
v2:
* Drop Error **errp argument to post_plug() handler [Paolo]
* Move post_plug() call outside if (dev->hotplugged)
The virtio-scsi command virtqueues run during hotplug. This creates the
possibility of race conditions since the guest can submit commands while the
monitor is performing hotplug.
See Patch 2 for a fix for the ->reset() vs event race condition that Zhengui Li
encountered.
Stefan Hajnoczi (2):
qdev: add HotplugHandler->post_plug() callback
virtio-scsi: fix hotplug ->reset() vs event race
include/hw/hotplug.h | 11 +++++++++++
hw/core/hotplug.c | 10 ++++++++++
hw/core/qdev.c | 4 ++++
hw/scsi/virtio-scsi.c | 11 ++++++++++-
4 files changed, 35 insertions(+), 1 deletion(-)
--
2.17.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [Qemu-devel] [PATCH v2 1/2] qdev: add HotplugHandler->post_plug() callback
2018-07-16 8:37 [Qemu-devel] [PATCH v2 0/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
@ 2018-07-16 8:37 ` Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
2018-07-16 9:28 ` [Qemu-devel] [PATCH v2 0/2] " Igor Mammedov
2 siblings, 0 replies; 6+ messages in thread
From: Stefan Hajnoczi @ 2018-07-16 8:37 UTC (permalink / raw)
To: qemu-devel
Cc: l00284672, Igor Mammedov, Fam Zheng, Michael S. Tsirkin,
Paolo Bonzini, Stefan Hajnoczi
The ->pre_plug() callback is invoked before the device is realized. The
->plug() callback is invoked when the device is being realized but
before it is reset.
This patch adds a ->post_plug() callback which is invoked after the
device has been reset. This callback is needed by HotplugHandlers that
need to wait until after ->reset().
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/hw/hotplug.h | 11 +++++++++++
hw/core/hotplug.c | 10 ++++++++++
hw/core/qdev.c | 4 ++++
3 files changed, 25 insertions(+)
diff --git a/include/hw/hotplug.h b/include/hw/hotplug.h
index 1a0516a479..51541d63e1 100644
--- a/include/hw/hotplug.h
+++ b/include/hw/hotplug.h
@@ -47,6 +47,8 @@ typedef void (*hotplug_fn)(HotplugHandler *plug_handler,
* @parent: Opaque parent interface.
* @pre_plug: pre plug callback called at start of device.realize(true)
* @plug: plug callback called at end of device.realize(true).
+ * @post_plug: post plug callback called after device.realize(true) and device
+ * reset
* @unplug_request: unplug request callback.
* Used as a means to initiate device unplug for devices that
* require asynchronous unplug handling.
@@ -61,6 +63,7 @@ typedef struct HotplugHandlerClass {
/* <public> */
hotplug_fn pre_plug;
hotplug_fn plug;
+ void (*post_plug)(HotplugHandler *plug_handler, DeviceState *plugged_dev);
hotplug_fn unplug_request;
hotplug_fn unplug;
} HotplugHandlerClass;
@@ -83,6 +86,14 @@ void hotplug_handler_pre_plug(HotplugHandler *plug_handler,
DeviceState *plugged_dev,
Error **errp);
+/**
+ * hotplug_handler_post_plug:
+ *
+ * Call #HotplugHandlerClass.post_plug callback of @plug_handler.
+ */
+void hotplug_handler_post_plug(HotplugHandler *plug_handler,
+ DeviceState *plugged_dev);
+
/**
* hotplug_handler_unplug_request:
*
diff --git a/hw/core/hotplug.c b/hw/core/hotplug.c
index 17ac986685..2253072d0e 100644
--- a/hw/core/hotplug.c
+++ b/hw/core/hotplug.c
@@ -35,6 +35,16 @@ void hotplug_handler_plug(HotplugHandler *plug_handler,
}
}
+void hotplug_handler_post_plug(HotplugHandler *plug_handler,
+ DeviceState *plugged_dev)
+{
+ HotplugHandlerClass *hdc = HOTPLUG_HANDLER_GET_CLASS(plug_handler);
+
+ if (hdc->post_plug) {
+ hdc->post_plug(plug_handler, plugged_dev);
+ }
+}
+
void hotplug_handler_unplug_request(HotplugHandler *plug_handler,
DeviceState *plugged_dev,
Error **errp)
diff --git a/hw/core/qdev.c b/hw/core/qdev.c
index cf0db4b6da..529b82de18 100644
--- a/hw/core/qdev.c
+++ b/hw/core/qdev.c
@@ -867,6 +867,10 @@ static void device_set_realized(Object *obj, bool value, Error **errp)
device_reset(dev);
}
dev->pending_deleted_event = false;
+
+ if (hotplug_ctrl) {
+ hotplug_handler_post_plug(hotplug_ctrl, dev);
+ }
} else if (!value && dev->realized) {
Error **local_errp = NULL;
QLIST_FOREACH(bus, &dev->child_bus, sibling) {
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race
2018-07-16 8:37 [Qemu-devel] [PATCH v2 0/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 1/2] qdev: add HotplugHandler->post_plug() callback Stefan Hajnoczi
@ 2018-07-16 8:37 ` Stefan Hajnoczi
2018-07-16 12:40 ` Michael S. Tsirkin
2018-07-16 9:28 ` [Qemu-devel] [PATCH v2 0/2] " Igor Mammedov
2 siblings, 1 reply; 6+ messages in thread
From: Stefan Hajnoczi @ 2018-07-16 8:37 UTC (permalink / raw)
To: qemu-devel
Cc: l00284672, Igor Mammedov, Fam Zheng, Michael S. Tsirkin,
Paolo Bonzini, Stefan Hajnoczi
There is a race condition during hotplug when iothread is used. It
occurs because virtio-scsi may be processing command queues in the
iothread while the monitor performs SCSI device hotplug.
When a SCSI device is hotplugged the HotplugHandler->plug() callback is
invoked and virtio-scsi emits a rescan event to the guest.
If the guest submits a SCSI command at this point then it may be
cancelled before hotplug completes. This happens because ->reset() is
called by hw/core/qdev.c:device_set_realized() after
HotplugHandler->plug() has been called and
hw/scsi/scsi-disk.c:scsi_disk_reset() purges all requests.
This patch uses the new HotplugHandler->post_plug() callback to emit the
rescan event after ->reset(). This eliminates the race conditions where
requests could be cancelled.
Reported-by: l00284672 <lizhengui@huawei.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/scsi/virtio-scsi.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
index 3aa99717e2..5a3057d1f8 100644
--- a/hw/scsi/virtio-scsi.c
+++ b/hw/scsi/virtio-scsi.c
@@ -797,8 +797,16 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
virtio_scsi_acquire(s);
blk_set_aio_context(sd->conf.blk, s->ctx);
virtio_scsi_release(s);
-
}
+}
+
+/* Announce the new device after it has been plugged */
+static void virtio_scsi_post_hotplug(HotplugHandler *hotplug_dev,
+ DeviceState *dev)
+{
+ VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
+ VirtIOSCSI *s = VIRTIO_SCSI(vdev);
+ SCSIDevice *sd = SCSI_DEVICE(dev);
if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
virtio_scsi_acquire(s);
@@ -968,6 +976,7 @@ static void virtio_scsi_class_init(ObjectClass *klass, void *data)
vdc->start_ioeventfd = virtio_scsi_dataplane_start;
vdc->stop_ioeventfd = virtio_scsi_dataplane_stop;
hc->plug = virtio_scsi_hotplug;
+ hc->post_plug = virtio_scsi_post_hotplug;
hc->unplug = virtio_scsi_hotunplug;
}
--
2.17.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v2 0/2] virtio-scsi: fix hotplug ->reset() vs event race
2018-07-16 8:37 [Qemu-devel] [PATCH v2 0/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 1/2] qdev: add HotplugHandler->post_plug() callback Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
@ 2018-07-16 9:28 ` Igor Mammedov
2 siblings, 0 replies; 6+ messages in thread
From: Igor Mammedov @ 2018-07-16 9:28 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: qemu-devel, l00284672, Fam Zheng, Michael S. Tsirkin, Paolo Bonzini
On Mon, 16 Jul 2018 09:37:30 +0100
Stefan Hajnoczi <stefanha@redhat.com> wrote:
> v2:
> * Drop Error **errp argument to post_plug() handler [Paolo]
> * Move post_plug() call outside if (dev->hotplugged)
>
> The virtio-scsi command virtqueues run during hotplug. This creates the
> possibility of race conditions since the guest can submit commands while the
> monitor is performing hotplug.
>
> See Patch 2 for a fix for the ->reset() vs event race condition that Zhengui Li
> encountered.
>
> Stefan Hajnoczi (2):
> qdev: add HotplugHandler->post_plug() callback
> virtio-scsi: fix hotplug ->reset() vs event race
>
> include/hw/hotplug.h | 11 +++++++++++
> hw/core/hotplug.c | 10 ++++++++++
> hw/core/qdev.c | 4 ++++
> hw/scsi/virtio-scsi.c | 11 ++++++++++-
> 4 files changed, 35 insertions(+), 1 deletion(-)
>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
@ 2018-07-16 12:40 ` Michael S. Tsirkin
2018-07-16 14:11 ` Paolo Bonzini
0 siblings, 1 reply; 6+ messages in thread
From: Michael S. Tsirkin @ 2018-07-16 12:40 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: qemu-devel, l00284672, Igor Mammedov, Fam Zheng, Paolo Bonzini
On Mon, Jul 16, 2018 at 09:37:32AM +0100, Stefan Hajnoczi wrote:
> There is a race condition during hotplug when iothread is used. It
> occurs because virtio-scsi may be processing command queues in the
> iothread while the monitor performs SCSI device hotplug.
>
> When a SCSI device is hotplugged the HotplugHandler->plug() callback is
> invoked and virtio-scsi emits a rescan event to the guest.
>
> If the guest submits a SCSI command at this point then it may be
> cancelled before hotplug completes. This happens because ->reset() is
> called by hw/core/qdev.c:device_set_realized() after
> HotplugHandler->plug() has been called and
> hw/scsi/scsi-disk.c:scsi_disk_reset() purges all requests.
>
> This patch uses the new HotplugHandler->post_plug() callback to emit the
> rescan event after ->reset(). This eliminates the race conditions where
> requests could be cancelled.
>
> Reported-by: l00284672 <lizhengui@huawei.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Fam Zheng <famz@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Pls merge through scsi tree.
> ---
> hw/scsi/virtio-scsi.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
> index 3aa99717e2..5a3057d1f8 100644
> --- a/hw/scsi/virtio-scsi.c
> +++ b/hw/scsi/virtio-scsi.c
> @@ -797,8 +797,16 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
> virtio_scsi_acquire(s);
> blk_set_aio_context(sd->conf.blk, s->ctx);
> virtio_scsi_release(s);
> -
> }
> +}
> +
> +/* Announce the new device after it has been plugged */
> +static void virtio_scsi_post_hotplug(HotplugHandler *hotplug_dev,
> + DeviceState *dev)
> +{
> + VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
> + VirtIOSCSI *s = VIRTIO_SCSI(vdev);
> + SCSIDevice *sd = SCSI_DEVICE(dev);
>
> if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
> virtio_scsi_acquire(s);
> @@ -968,6 +976,7 @@ static void virtio_scsi_class_init(ObjectClass *klass, void *data)
> vdc->start_ioeventfd = virtio_scsi_dataplane_start;
> vdc->stop_ioeventfd = virtio_scsi_dataplane_stop;
> hc->plug = virtio_scsi_hotplug;
> + hc->post_plug = virtio_scsi_post_hotplug;
> hc->unplug = virtio_scsi_hotunplug;
> }
>
> --
> 2.17.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race
2018-07-16 12:40 ` Michael S. Tsirkin
@ 2018-07-16 14:11 ` Paolo Bonzini
0 siblings, 0 replies; 6+ messages in thread
From: Paolo Bonzini @ 2018-07-16 14:11 UTC (permalink / raw)
To: Michael S. Tsirkin, Stefan Hajnoczi
Cc: qemu-devel, l00284672, Igor Mammedov, Fam Zheng
On 16/07/2018 14:40, Michael S. Tsirkin wrote:
> On Mon, Jul 16, 2018 at 09:37:32AM +0100, Stefan Hajnoczi wrote:
>> There is a race condition during hotplug when iothread is used. It
>> occurs because virtio-scsi may be processing command queues in the
>> iothread while the monitor performs SCSI device hotplug.
>>
>> When a SCSI device is hotplugged the HotplugHandler->plug() callback is
>> invoked and virtio-scsi emits a rescan event to the guest.
>>
>> If the guest submits a SCSI command at this point then it may be
>> cancelled before hotplug completes. This happens because ->reset() is
>> called by hw/core/qdev.c:device_set_realized() after
>> HotplugHandler->plug() has been called and
>> hw/scsi/scsi-disk.c:scsi_disk_reset() purges all requests.
>>
>> This patch uses the new HotplugHandler->post_plug() callback to emit the
>> rescan event after ->reset(). This eliminates the race conditions where
>> requests could be cancelled.
>>
>> Reported-by: l00284672 <lizhengui@huawei.com>
>> Cc: Paolo Bonzini <pbonzini@redhat.com>
>> Cc: Fam Zheng <famz@redhat.com>
>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
>
> Pls merge through scsi tree.
Will do, thanks Stefan.
Paolo
>
>> ---
>> hw/scsi/virtio-scsi.c | 11 ++++++++++-
>> 1 file changed, 10 insertions(+), 1 deletion(-)
>>
>> diff --git a/hw/scsi/virtio-scsi.c b/hw/scsi/virtio-scsi.c
>> index 3aa99717e2..5a3057d1f8 100644
>> --- a/hw/scsi/virtio-scsi.c
>> +++ b/hw/scsi/virtio-scsi.c
>> @@ -797,8 +797,16 @@ static void virtio_scsi_hotplug(HotplugHandler *hotplug_dev, DeviceState *dev,
>> virtio_scsi_acquire(s);
>> blk_set_aio_context(sd->conf.blk, s->ctx);
>> virtio_scsi_release(s);
>> -
>> }
>> +}
>> +
>> +/* Announce the new device after it has been plugged */
>> +static void virtio_scsi_post_hotplug(HotplugHandler *hotplug_dev,
>> + DeviceState *dev)
>> +{
>> + VirtIODevice *vdev = VIRTIO_DEVICE(hotplug_dev);
>> + VirtIOSCSI *s = VIRTIO_SCSI(vdev);
>> + SCSIDevice *sd = SCSI_DEVICE(dev);
>>
>> if (virtio_vdev_has_feature(vdev, VIRTIO_SCSI_F_HOTPLUG)) {
>> virtio_scsi_acquire(s);
>> @@ -968,6 +976,7 @@ static void virtio_scsi_class_init(ObjectClass *klass, void *data)
>> vdc->start_ioeventfd = virtio_scsi_dataplane_start;
>> vdc->stop_ioeventfd = virtio_scsi_dataplane_stop;
>> hc->plug = virtio_scsi_hotplug;
>> + hc->post_plug = virtio_scsi_post_hotplug;
>> hc->unplug = virtio_scsi_hotunplug;
>> }
>>
>> --
>> 2.17.1
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-07-16 14:11 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-07-16 8:37 [Qemu-devel] [PATCH v2 0/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 1/2] qdev: add HotplugHandler->post_plug() callback Stefan Hajnoczi
2018-07-16 8:37 ` [Qemu-devel] [PATCH v2 2/2] virtio-scsi: fix hotplug ->reset() vs event race Stefan Hajnoczi
2018-07-16 12:40 ` Michael S. Tsirkin
2018-07-16 14:11 ` Paolo Bonzini
2018-07-16 9:28 ` [Qemu-devel] [PATCH v2 0/2] " Igor Mammedov
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