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Tsirkin" , Cindy Lu , Xuan Zhuo , linux-kernel@vger.kernel.org, Maxime Coquelin , Stefano Garzarella , Laurent Vivier , Yongji Xie , virtualization@lists.linux.dev X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 2liidBD1Nx6M-mgD-zzFbHflY-5xboKYPb1b1s37QRg_1773287767 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Mar 11, 2026 at 3:08=E2=80=AFAM Eugenio P=C3=A9rez wrote: > > Add an ioctl to allow VDUSE instances to query the available features > supported by the kernel module. > > Signed-off-by: Eugenio P=C3=A9rez > --- > A simple u64 bitmap is used for feature flags. While a flexible array > could support indefinite expansion, 64 bits is sufficient for the > foreseeable future and simplifies the implementation. > > Also, dev_dbg is used for logging rather than dev_err as these can be > triggered from userspace. > --- > v3: > * Remove check for API_VERSION < 2 > * Add comment about struct vduse_dev_config:vduse_features is only valid > if VDUSE_GET_FEATURES success. > > v2: > * return -EINVAL if ioctl called with version < 2, so userland visible > reply is kept (Jason). > --- > drivers/vdpa/vdpa_user/vduse_dev.c | 7 +++++++ > include/uapi/linux/vduse.h | 7 ++++++- > 2 files changed, 13 insertions(+), 1 deletion(-) > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/= vduse_dev.c > index d1da7c15d98b..17e0358d3a68 100644 > --- a/drivers/vdpa/vdpa_user/vduse_dev.c > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c > @@ -52,6 +52,9 @@ > > #define IRQ_UNBOUND -1 > > +/* Supported VDUSE features */ > +static const uint64_t vduse_features; > + > /* > * VDUSE instance have not asked the vduse API version, so assume 0. > * > @@ -2207,6 +2210,10 @@ static long vduse_ioctl(struct file *file, unsigne= d int cmd, > ret =3D vduse_destroy_dev(name); > break; > } > + case VDUSE_GET_FEATURES: > + ret =3D put_user(vduse_features, (u64 __user *)argp); > + break; > + > default: > ret =3D -EINVAL; > break; > diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h > index 361eea511c21..e9b5f32a452d 100644 > --- a/include/uapi/linux/vduse.h > +++ b/include/uapi/linux/vduse.h > @@ -33,6 +33,7 @@ > * @vq_align: the allocation alignment of virtqueue's metadata > * @ngroups: number of vq groups that VDUSE device declares > * @nas: number of address spaces that VDUSE device declares > + * @vduse_features: VDUSE features > * @reserved: for future use, needs to be initialized to zero > * @config_size: the size of the configuration space > * @config: the buffer of the configuration space > @@ -49,7 +50,8 @@ struct vduse_dev_config { > __u32 vq_align; > __u32 ngroups; /* if VDUSE_API_VERSION >=3D 1 */ > __u32 nas; /* if VDUSE_API_VERSION >=3D 1 */ > - __u32 reserved[11]; > + __u64 vduse_features; /* if VDUSE_GET_FEATURES is not EINVAL */ > + __u32 reserved[9]; If we go with VDUSE_GET_FEATURES, I'd perfer to go with VDUSE_SET_FEATURES intead of this. But we can hear from others. > __u32 config_size; > __u8 config[]; > }; > @@ -63,6 +65,9 @@ struct vduse_dev_config { > */ > #define VDUSE_DESTROY_DEV _IOW(VDUSE_BASE, 0x03, char[VDUSE_NAME_MA= X]) > > +/* Get the VDUSE supported features */ > +#define VDUSE_GET_FEATURES _IOR(VDUSE_BASE, 0x04, __u64) > + > /* The ioctls for VDUSE device (/dev/vduse/$NAME) */ > > /** > -- > 2.53.0 > Thanks