linux-kernel - Re: [PATCH 4/6] vduse: add VDUSE_GET

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CACGkMEtmw-ofTt-EVH7o4dwZEk7qtXCuAsXyb7R71693UW9-RA@mail.gmail.com>
Date: Thu, 29 Jan 2026 10:10:29 +0800
From: Jason Wang <jasowang@...hat.com>
To: Eugenio Pérez <eperezma@...hat.com>
Cc: "Michael S . Tsirkin" <mst@...hat.com>, Xuan Zhuo <xuanzhuo@...ux.alibaba.com>, 
	Cindy Lu <lulu@...hat.com>, Laurent Vivier <lvivier@...hat.com>, 
	Stefano Garzarella <sgarzare@...hat.com>, linux-kernel@...r.kernel.org, 
	Maxime Coquelin <mcoqueli@...hat.com>, Yongji Xie <xieyongji@...edance.com>, 
	virtualization@...ts.linux.dev
Subject: Re: [PATCH 4/6] vduse: add VDUSE_GET_FEATURES ioctl

On Wed, Jan 28, 2026 at 8:45 PM Eugenio Pérez <eperezma@...hat.com> wrote:
>
> Add an ioctl to allow VDUSE instances to query the available features
> supported by the kernel module.
>
> Signed-off-by: Eugenio Pérez <eperezma@...hat.com>
> ---
> 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.
> ---
>  drivers/vdpa/vdpa_user/vduse_dev.c | 28 ++++++++++++++++++++++++++++
>  include/uapi/linux/vduse.h         |  7 ++++++-
>  2 files changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> index 551ccde0b856..e7da69c2ad71 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.
>   *
> @@ -1977,6 +1980,19 @@ static bool vduse_validate_config(struct vduse_dev_config *config,
>                          sizeof(config->reserved)))
>                 return false;
>
> +       if (api_version < VDUSE_API_VERSION_2) {
> +               if (config->vduse_features) {
> +                       dev_dbg(vduse_ctrl_dev,
> +                               "config->vduse_features with version %llu",
> +                               api_version);
> +                       return false;
> +               }
> +       } else {
> +               if (config->vduse_features & ~vduse_features)
> +                       return false;
> +       }
> +
> +
>         if (api_version < VDUSE_API_VERSION_1 &&
>             (config->ngroups || config->nas))
>                 return false;
> @@ -2237,6 +2253,18 @@ static long vduse_ioctl(struct file *file, unsigned int cmd,
>                 ret = vduse_destroy_dev(name);
>                 break;
>         }
> +       case VDUSE_GET_FEATURES:
> +               if (control->api_version < VDUSE_API_VERSION_2) {
> +                       dev_dbg(vduse_ctrl_dev,
> +                               "VDUSE_GET_FEATURES ioctl with version %llu",
> +                               control->api_version);
> +                       ret = -ENOIOCTLCMD;

Should we stick to -EINVAL (see below)?


> +                       break;
> +               }
> +
> +               ret = put_user(vduse_features, (u64 __user *)argp);
> +               break;
> +
>         default:
>                 ret = -EINVAL;
>                 break;
> diff --git a/include/uapi/linux/vduse.h b/include/uapi/linux/vduse.h
> index dea89ed281a7..1f68e556cbf2 100644
> --- a/include/uapi/linux/vduse.h
> +++ b/include/uapi/linux/vduse.h
> @@ -37,6 +37,7 @@
>   * @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
> @@ -53,7 +54,8 @@ struct vduse_dev_config {
>         __u32 vq_align;
>         __u32 ngroups; /* if VDUSE_API_VERSION >= 1 */
>         __u32 nas; /* if VDUSE_API_VERSION >= 1 */
> -       __u32 reserved[11];
> +       __u64 vduse_features;
> +       __u32 reserved[9];
>         __u32 config_size;
>         __u8 config[];
>  };
> @@ -67,6 +69,9 @@ struct vduse_dev_config {
>   */
>  #define VDUSE_DESTROY_DEV      _IOW(VDUSE_BASE, 0x03, char[VDUSE_NAME_MAX])
>
> +/* Get the VDUSE supported features */
> +#define VDUSE_GET_FEATURES     _IOR(VDUSE_BASE, 0x04, __u64)
> +
>  /* The ioctls for VDUSE device (/dev/vduse/$NAME) */
>
>  /**
> --
> 2.52.0
>

Thanks