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 Monné <[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
