On 1/10/2022 8:46 PM, Jason Wang wrote:
On Tue, Jan 11, 2022 at 9:30 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
On 1/9/2022 10:05 PM, Jason Wang wrote:
在 2022/1/8 上午9:23, Si-Wei Liu 写道:
On 1/6/2022 9:08 PM, Jason Wang wrote:
在 2022/1/7 上午8:33, Si-Wei Liu 写道:
On 1/5/2022 3:46 AM, Eli Cohen wrote:
Add wrappers to get/set status and protect these operations with
cf_mutex to serialize these operations with respect to get/set config
operations.
Signed-off-by: Eli Cohen <elic@xxxxxxxxxx>
---
drivers/vdpa/vdpa.c | 19 +++++++++++++++++++
drivers/vhost/vdpa.c | 7 +++----
drivers/virtio/virtio_vdpa.c | 3 +--
include/linux/vdpa.h | 3 +++
4 files changed, 26 insertions(+), 6 deletions(-)
diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
index 42d71d60d5dc..5134c83c4a22 100644
--- a/drivers/vdpa/vdpa.c
+++ b/drivers/vdpa/vdpa.c
@@ -21,6 +21,25 @@ static LIST_HEAD(mdev_head);
static DEFINE_MUTEX(vdpa_dev_mutex);
static DEFINE_IDA(vdpa_index_ida);
+u8 vdpa_get_status(struct vdpa_device *vdev)
+{
+ u8 status;
+
+ mutex_lock(&vdev->cf_mutex);
+ status = vdev->config->get_status(vdev);
+ mutex_unlock(&vdev->cf_mutex);
+ return status;
+}
+EXPORT_SYMBOL(vdpa_get_status);
+
+void vdpa_set_status(struct vdpa_device *vdev, u8 status)
+{
+ mutex_lock(&vdev->cf_mutex);
+ vdev->config->set_status(vdev, status);
+ mutex_unlock(&vdev->cf_mutex);
+}
+EXPORT_SYMBOL(vdpa_set_status);
+
static struct genl_family vdpa_nl_family;
static int vdpa_dev_probe(struct device *d)
diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
index ebaa373e9b82..d9d499465e2e 100644
--- a/drivers/vhost/vdpa.c
+++ b/drivers/vhost/vdpa.c
@@ -142,10 +142,9 @@ static long vhost_vdpa_get_device_id(struct
vhost_vdpa *v, u8 __user *argp)
static long vhost_vdpa_get_status(struct vhost_vdpa *v, u8
__user *statusp)
{
struct vdpa_device *vdpa = v->vdpa;
- const struct vdpa_config_ops *ops = vdpa->config;
u8 status;
- status = ops->get_status(vdpa);
+ status = vdpa_get_status(vdpa);
Not sure why we need to take cf_mutex here. Appears to me only
setters (set_status and reset) need to take the lock in this function.
You may be right but it doesn't harm and it is guaranteed to be
correct if we protect it with mutex here.
Is it more for future proof?
I think so.
I guess in this situation it would be better defer to the future patch
to add such locking or wrapper, although right now there are just two
additional calls taking the lock needlessly when vhost_vdpa_get_status
is called. Maybe it's just me but I'm worried some future patch may
calls the locked API wrapper thousands of times unintendedly, then the
overhead becomes quite obvious.
I'm fine to remove this if others agree on this.
It looks Parav acked on this. Anyone else?
Ok, but IMHO it might be better to get some comment here, otherwise
it's quite confusing why the lock needs to be held. vhost_vdpa had
done its own serialization in vhost_vdpa_unlocked_ioctl() through
vhost_dev`mutex.
Right, but they are done for different levels, one is for vhost_dev
antoher is for vdpa_dev.
The cf_mutex is introduced to serialize the command line configure
thread (via netlink) and the upstream driver calls from either the
vhost_dev or virtio_dev. I don't see a case, even in future, where the
netlink thread needs to update the virtio status on the fly. Can you
enlighten me why that is at all possible?
After some thought I don't see a case. I can think of NEEDS_RESET but
it should come with a config interrupt so we're probably fine without
the mutex here.
True, it's quite unlikely for netlink to alter the status directly while
driver is running. More likely the out of band reset has to reach the
guest driver first for it to be aware, which would then initiate the
vhost call down to vhost-vdpa through the same path.
-Siwei
Thanks
Thanks,
-Siwei
Thanks
-Siwei
Thanks
if (copy_to_user(statusp, &status, sizeof(status)))
return -EFAULT;
@@ -164,7 +163,7 @@ static long vhost_vdpa_set_status(struct
vhost_vdpa *v, u8 __user *statusp)
if (copy_from_user(&status, statusp, sizeof(status)))
return -EFAULT;
- status_old = ops->get_status(vdpa);
+ status_old = vdpa_get_status(vdpa);
Ditto.
/*
* Userspace shouldn't remove status bits unless reset the
@@ -182,7 +181,7 @@ static long vhost_vdpa_set_status(struct
vhost_vdpa *v, u8 __user *statusp)
if (ret)
return ret;
} else
- ops->set_status(vdpa, status);
+ vdpa_set_status(vdpa, status);
The reset() call in the if branch above needs to take the cf_mutex,
the same way as that for set_status(). The reset() is effectively
set_status(vdpa, 0).
Thanks,
-Siwei
if ((status & VIRTIO_CONFIG_S_DRIVER_OK) && !(status_old &
VIRTIO_CONFIG_S_DRIVER_OK))
for (i = 0; i < nvqs; i++)
diff --git a/drivers/virtio/virtio_vdpa.c
b/drivers/virtio/virtio_vdpa.c
index a84b04ba3195..76504559bc25 100644
--- a/drivers/virtio/virtio_vdpa.c
+++ b/drivers/virtio/virtio_vdpa.c
@@ -91,9 +91,8 @@ static u8 virtio_vdpa_get_status(struct
virtio_device *vdev)
static void virtio_vdpa_set_status(struct virtio_device *vdev,
u8 status)
{
struct vdpa_device *vdpa = vd_get_vdpa(vdev);
- const struct vdpa_config_ops *ops = vdpa->config;
- return ops->set_status(vdpa, status);
+ return vdpa_set_status(vdpa, status);
}
static void virtio_vdpa_reset(struct virtio_device *vdev)
diff --git a/include/linux/vdpa.h b/include/linux/vdpa.h
index 9cc4291a79b3..ae047fae2603 100644
--- a/include/linux/vdpa.h
+++ b/include/linux/vdpa.h
@@ -408,6 +408,9 @@ void vdpa_get_config(struct vdpa_device *vdev,
unsigned int offset,
void *buf, unsigned int len);
void vdpa_set_config(struct vdpa_device *dev, unsigned int offset,
const void *buf, unsigned int length);
+u8 vdpa_get_status(struct vdpa_device *vdev);
+void vdpa_set_status(struct vdpa_device *vdev, u8 status);
+
/**
* struct vdpa_mgmtdev_ops - vdpa device ops
* @dev_add: Add a vdpa device using alloc and register
_______________________________________________
Virtualization mailing list
Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
https://lists.linuxfoundation.org/mailman/listinfo/virtualization
