On Thu, Nov 07, 2024 at 03:12:49PM +0800, Cindy Lu wrote:
On Tue, Nov 5, 2024 at 6:32 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:
On Tue, Nov 05, 2024 at 03:25:26PM +0800, Cindy Lu wrote:
>Add a new UAPI to enable setting the vhost device to task mode.
>The userspace application can use VHOST_SET_INHERIT_FROM_OWNER
>to configure the mode if necessary.
>This setting must be applied before VHOST_SET_OWNER, as the worker
>will be created in the VHOST_SET_OWNER function
>
>Signed-off-by: Cindy Lu <lulu@xxxxxxxxxx>
>---
> drivers/vhost/vhost.c | 15 ++++++++++++++-
> include/uapi/linux/vhost.h | 2 ++
> 2 files changed, 16 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index c17dc01febcc..70c793b63905 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -2274,8 +2274,9 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
> {
> struct eventfd_ctx *ctx;
> u64 p;
>- long r;
>+ long r = 0;
I don't know if something is missing in this patch, but I am confused:
`r` is set few lines below...
> int i, fd;
>+ bool inherit_owner;
>
> /* If you are not the owner, you can become one */
> if (ioctl == VHOST_SET_OWNER) {
...
/* You must be the owner to do anything else */
r = vhost_dev_check_owner(d);
if (r)
goto done;
So, why we are now initializing it to 0?
r = 0 mean return successfully here.
Therefore, in the case VHOST_SET_INHERIT_FROM_OWNER function, I don't
need to set it again and can simply return.
....
if (vhost_dev_has_owner(d))
break;
.....
Okay, but vhost_dev_check_owner() already set it to 0, so we can avoid
that, no?
>@@ -2332,6 +2333,18 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
> if (ctx)
> eventfd_ctx_put(ctx);
> break;
>+ case VHOST_SET_INHERIT_FROM_OWNER:
>+ /*inherit_owner can only be modified before owner is set*/
>+ if (vhost_dev_has_owner(d))
And here, how this check can be false, if at the beginning of the
function we call vhost_dev_check_owner()?
Maybe your intention was to add this code before the
`vhost_dev_check_owner()` call, so this should explain why initialize
`r` to 0, but I'm not sure.
Yes, in the function beginning, the code is
if (ioctl == VHOST_SET_OWNER) {
r = vhost_dev_set_owner(d);
goto done;
}
if the ioctl is not VHOST_SET_OWNER, then the code will not run the
function vhost_dev_set_owner.
Sorry, I meant vhost_dev_check_owner(), not vhost_dev_set_owner().
I'll try to explain again.
After applying this series we have this code:
long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
{
struct eventfd_ctx *ctx;
u64 p;
long r = 0;
int i, fd;
bool inherit_owner;
/* If you are not the owner, you can become one */
if (ioctl == VHOST_SET_OWNER) {
r = vhost_dev_set_owner(d);
goto done;
}
/* You must be the owner to do anything else */
r = vhost_dev_check_owner(d);
if (r)
goto done;
switch (ioctl) {
...
case VHOST_SET_INHERIT_FROM_OWNER:
/*inherit_owner can only be modified before owner is
* set*/
if (vhost_dev_has_owner(d))
break;
IIUC this check is always true, so we always call `break` because at
the beginning of this function we call vhost_dev_check_owner() which
if `dev->mm != current->mm` (so it can't be null I guess) jumps directly
into `done`, returning an error.
So I still don't understand in which condition we can run the code after
this check.
Thanks,
Stefano
if (copy_from_user(&inherit_owner, argp,
sizeof(inherit_owner))) {
r = -EFAULT;
break;
}
d->inherit_owner = inherit_owner;
break;
This ioctl is used by userspace applications, so we cannot be certain
of the type and sequence of their calls; therefore, I added this
check.
>+ break;
Should we return an error (e.g. -EPERM) in this case?
sure，will add this back
thanks
Cindy
>+
>+ if (copy_from_user(&inherit_owner, argp,
>+ sizeof(inherit_owner))) {
>+ r = -EFAULT;
>+ break;
>+ }
>+ d->inherit_owner = inherit_owner;
>+ break;
> default:
> r = -ENOIOCTLCMD;
> break;
>diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
>index b95dd84eef2d..1e192038633d 100644
>--- a/include/uapi/linux/vhost.h
>+++ b/include/uapi/linux/vhost.h
>@@ -235,4 +235,6 @@
> */
> #define VHOST_VDPA_GET_VRING_SIZE _IOWR(VHOST_VIRTIO, 0x82, \
> struct vhost_vring_state)
>+
Please add a documentation here, this is UAPI, so the user should
know what this ioctl does based on the parameter.
Thanks,
Stefano
>+#define VHOST_SET_INHERIT_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, bool)
> #endif
>--
>2.45.0
>
