> -----Original Message-----
> From: Roger Pau Monne <[email protected]>
> Sent: 18 January 2021 15:34
> To: [email protected]
> Cc: Roger Pau Monne <[email protected]>; Arthur Borsboom 
> <[email protected]>; Stefano
> Stabellini <[email protected]>; Anthony Perard 
> <[email protected]>; Paul Durrant
> <[email protected]>; Kevin Wolf <[email protected]>; Max Reitz <[email protected]>; 
> xen-
> [email protected]; [email protected]
> Subject: [PATCH] xen-block: fix reporting of discard feature
> 
> Linux blkfront expects both "discard-granularity" and
> "discard-alignment" present on xenbus in order to properly enable the
> feature, not exposing "discard-alignment" left some Linux blkfront
> versions with a broken discard setup. This has also been addressed in
> Linux with:
> 
> https://lore.kernel.org/lkml/[email protected]/T/#u
> 
> Fix QEMU to report a "discard-alignment" of 0, in order for it to work
> with older Linux frontends.
> 
> Reported-by: Arthur Borsboom <[email protected]>
> Signed-off-by: Roger Pau MonnĂ© <[email protected]>

Reviewed-by: Paul Durrant <[email protected]>

> ---
> Cc: Stefano Stabellini <[email protected]>
> Cc: Anthony Perard <[email protected]>
> Cc: Paul Durrant <[email protected]>
> Cc: Kevin Wolf <[email protected]>
> Cc: Max Reitz <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
>  hw/block/xen-block.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/hw/block/xen-block.c b/hw/block/xen-block.c
> index 718d886e5c..246d9c23a2 100644
> --- a/hw/block/xen-block.c
> +++ b/hw/block/xen-block.c
> @@ -253,6 +253,7 @@ static void xen_block_realize(XenDevice *xendev, Error 
> **errp)
>          xen_device_backend_printf(xendev, "feature-discard", "%u", 1);
>          xen_device_backend_printf(xendev, "discard-granularity", "%u",
>                                    conf->discard_granularity);
> +        xen_device_backend_printf(xendev, "discard-alignment", "%u", 0);
>      }
> 
>      xen_device_backend_printf(xendev, "feature-flush-cache", "%u", 1);
> --
> 2.29.2



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