On Fri, Jul 31, 2026 at 03:10:24PM -0700, Dongli Zhang wrote:
> max_io_vqs is currently validated only when a vhost-scsi device is opened.
> This allows sysfs to show values larger than the driver will actually use,
> e.g. writing 2048 succeeds even though vhost_scsi_open() later clamps it to
> VHOST_SCSI_MAX_IO_VQ. This makes the sysfs value differ from the value that
> will actually be used.
>
> hv# echo 2048 > /sys/module/vhost_scsi/parameters/max_io_vqs
>
> hv# cat /sys/module/vhost_scsi/parameters/max_io_vqs
> 2048
>
> [ 315.630495] Invalid max_io_vqs of 2048. Using 1024.
>
> Use a module parameter callback to reject out-of-range updates when the
> parameter is written. This keeps the visible parameter value consistent
> with the effective queue limit.
>
> With the parameter value kept in range, remove the duplicate validation
> from vhost_scsi_open().
>
> Invalid values now fail with -EINVAL at write/load time instead of being
> accepted and silently adjusted later when the device is opened.
>
> Signed-off-by: Dongli Zhang <[email protected]>
why should we change userspace visible behaviour now?
> ---
> drivers/vhost/scsi.c | 27 ++++++++++++++++-----------
> 1 file changed, 16 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 0c0634eea144..c138c29ce3dd 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -210,7 +210,20 @@ static const int vhost_scsi_bits[] = {
> #define VHOST_SCSI_MAX_EVENT 128
>
> static unsigned vhost_scsi_max_io_vqs = 128;
> -module_param_named(max_io_vqs, vhost_scsi_max_io_vqs, uint, 0644);
> +
> +static int vhost_scsi_set_max_io_vqs(const char *val,
> + const struct kernel_param *kp)
> +{
> + return param_set_uint_minmax(val, kp, 1, VHOST_SCSI_MAX_IO_VQ);
> +}
> +
> +static const struct kernel_param_ops vhost_scsi_max_io_vqs_op = {
> + .set = vhost_scsi_set_max_io_vqs,
> + .get = param_get_uint,
> +};
> +
> +module_param_cb(max_io_vqs, &vhost_scsi_max_io_vqs_op,
> + &vhost_scsi_max_io_vqs, 0644);
> MODULE_PARM_DESC(max_io_vqs, "Set the max number of IO virtqueues a vhost
> scsi device can support. The default is 128. The max is 1024.");
>
> struct vhost_scsi_virtqueue {
> @@ -2273,22 +2286,14 @@ static int vhost_scsi_open(struct inode *inode,
> struct file *f)
> struct vhost_scsi_virtqueue *svq;
> struct vhost_scsi *vs;
> struct vhost_virtqueue **vqs;
> - int r = -ENOMEM, i, nvqs = vhost_scsi_max_io_vqs;
> + int r = -ENOMEM, i, nvqs;
>
> vs = kvzalloc_obj(*vs);
> if (!vs)
> goto err_vs;
> vs->inline_sg_cnt = vhost_scsi_inline_sg_cnt;
>
> - if (nvqs > VHOST_SCSI_MAX_IO_VQ) {
> - pr_err("Invalid max_io_vqs of %d. Using %d.\n", nvqs,
> - VHOST_SCSI_MAX_IO_VQ);
> - nvqs = VHOST_SCSI_MAX_IO_VQ;
> - } else if (nvqs == 0) {
> - pr_err("Invalid max_io_vqs of %d. Using 1.\n", nvqs);
> - nvqs = 1;
> - }
> - nvqs += VHOST_SCSI_VQ_IO;
> + nvqs = vhost_scsi_max_io_vqs + VHOST_SCSI_VQ_IO;
>
> vs->old_inflight = kmalloc_objs(*vs->old_inflight, nvqs,
> GFP_KERNEL | __GFP_ZERO);
> --
> 2.43.5
