On Wed, Jan 13, 2021 at 11:43:50AM +0100, Arthur Borsboom wrote:
> When performing the following command in a Xen VM the call trace below is
> generated.
> 
>     sudo fstrim -v /
> 
> Xen VM host: Xen 4.14.0
> Xen Dom0: Linux 4.19.14
> Xen DomX: Linux 5.10.6
> 
> The code in the kernel triggering this trace is the following.
> 
>         /* In case the discard granularity isn't set by buggy device driver
> */
>         if (WARN_ON_ONCE(!q->limits.discard_granularity)) {
>                 char dev_name[BDEVNAME_SIZE];
> 
>                 bdevname(bdev, dev_name);
>                 pr_err_ratelimited("%s: Error: discard_granularity is
> 0.\n", dev_name);
>                 return -EOPNOTSUPP;
>         }

So it seems like the underlying storage in dom0 doesn't support
discard, and hence the feature don't get setup on the frontend?

Can you print the output of `xenstore-ls -fp` executed from dom0 when
the guest is running? That way I could see which features the backend
is exposing.

Thanks, Roger.

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