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Message-ID: <trrpnhe3qahveeizjlwfp33thudcw5jcmh3uunllucgur4txub@gm2k3p4sx6in>
Date: Mon, 7 Oct 2024 15:37:40 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Cindy Lu <lulu@...hat.com>
Cc: jasowang@...hat.com, mst@...hat.com, michael.christie@...cle.com,
linux-kernel@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 7/7] vhost: Add new UAPI to support change to task mode
On Fri, Oct 04, 2024 at 09:58:21AM GMT, Cindy Lu wrote:
>Add a new UAPI to support setting the vhost device to
>use task mode. The user space application needs to use
>VHOST_SET_INHERIT_FROM_OWNER to set the mode.
>This setting must be set before VHOST_SET_OWNER is set.
Why?
>
>Signed-off-by: Cindy Lu <lulu@...hat.com>
>---
> drivers/vhost/vhost.c | 18 +++++++++++++++++-
> include/uapi/linux/vhost.h | 2 ++
> 2 files changed, 19 insertions(+), 1 deletion(-)
>
>diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>index 08c9e77916ca..0e5c81026acd 100644
>--- a/drivers/vhost/vhost.c
>+++ b/drivers/vhost/vhost.c
>@@ -2341,8 +2341,24 @@ 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;
> int i, fd;
>+ bool inherit_owner;
^
This can be moved ...
>+
>+ if (ioctl == VHOST_SET_INHERIT_FROM_OWNER) {
^
... here.
>+ /* Is there an owner already? */
This comment is superfluous, I would instead explain why there has to be
an owner, what problem would we have if not?
>+ if (vhost_dev_has_owner(d)) {
>+ r = -EBUSY;
>+ goto done;
>+ }
>+ if (copy_from_user(&inherit_owner, argp,
>+ sizeof(inherit_owner))) {
>+ r = -EFAULT;
>+ goto done;
>+ }
>+ enforce_inherit_owner = inherit_owner;
mmmm, I'm confused.
IIUC with this change, an user, for example, can call
VHOST_SET_INHERIT_FROM_OWNER on /dev/vhost-vsock and change the
behaviour of /dev/vhost-net.
Is that really what we want?
Maybe it's better if the module parameter controls the default of any
device, but the ioctl changes the behavior only for that device.
>+ goto done;
>+ }
>
> /* If you are not the owner, you can become one */
> if (ioctl == VHOST_SET_OWNER) {
>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 documentation here.
>+#define VHOST_SET_INHERIT_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, bool)
^
Please, add a tab like we did
for all previous definitions.
Thanks,
Stefano
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