[PATCH] xen-block: fix reporting of discard feature

[PATCH] xen-block: fix reporting of discard feature

[roger.pau--- via]

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/20210118151528.81668-1-roger.pau@citrix.com/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 <arthurborsboom@gmail.com>
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Paul Durrant <paul@xen.org>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Max Reitz <mreitz@redhat.com>
Cc: xen-devel@lists.xenproject.org
Cc: qemu-block@nongnu.org
---
 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

RE: [PATCH] xen-block: fix reporting of discard feature

[Paul Durrant]

> -----Original Message-----
> From: Roger Pau Monne <roger.pau@citrix.com>
> Sent: 18 January 2021 15:34
> To: qemu-devel@nongnu.org
> Cc: Roger Pau Monne <roger.pau@citrix.com>; Arthur Borsboom <arthurborsboom@gmail.com>; Stefano
> Stabellini <sstabellini@kernel.org>; Anthony Perard <anthony.perard@citrix.com>; Paul Durrant
> <paul@xen.org>; Kevin Wolf <kwolf@redhat.com>; Max Reitz <mreitz@redhat.com>; xen-
> devel@lists.xenproject.org; qemu-block@nongnu.org
> 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/20210118151528.81668-1-roger.pau@citrix.com/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 <arthurborsboom@gmail.com>
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Paul Durrant <paul@xen.org>

> ---
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Anthony Perard <anthony.perard@citrix.com>
> Cc: Paul Durrant <paul@xen.org>
> Cc: Kevin Wolf <kwolf@redhat.com>
> Cc: Max Reitz <mreitz@redhat.com>
> Cc: xen-devel@lists.xenproject.org
> Cc: qemu-block@nongnu.org
> ---
>  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

Re: [PATCH] xen-block: fix reporting of discard feature

[Kevin Wolf]

Am 18.01.2021 um 16:49 hat Paul Durrant geschrieben:
> > -----Original Message-----
> > From: Roger Pau Monne <roger.pau@citrix.com>
> > Sent: 18 January 2021 15:34
> > To: qemu-devel@nongnu.org
> > Cc: Roger Pau Monne <roger.pau@citrix.com>; Arthur Borsboom <arthurborsboom@gmail.com>; Stefano
> > Stabellini <sstabellini@kernel.org>; Anthony Perard <anthony.perard@citrix.com>; Paul Durrant
> > <paul@xen.org>; Kevin Wolf <kwolf@redhat.com>; Max Reitz <mreitz@redhat.com>; xen-
> > devel@lists.xenproject.org; qemu-block@nongnu.org
> > 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/20210118151528.81668-1-roger.pau@citrix.com/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 <arthurborsboom@gmail.com>
> > Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Reviewed-by: Paul Durrant <paul@xen.org>

Thanks, applied to the block branch.

Kevin