[PULL 1/2] hw/nvme: re-enable wzds bit in namespace dlfeat

[Klaus Jensen <its@irrelevant.dk>]

From: Pankaj Raghav <p.raghav@samsung.com>

dlfeat was changed from 0x9 to 0x1 when PI support was added.
It was removed because we can't rely on unmap and have to physically
clear it to get the checksums right but that doesnt mean that we do not
support the bit.

The spec says that if wzds is enabled, then the controller supports
deallocate (DEAC) on write zeroes. But DEAC bit in write zeroes command
is only a hint, the controller might choose to physically write zeroes in
those areas.

As we are sending write zeroes command with BDRV_REQ_MAY_UNMAP to the
underlying block device anyway (if the unmap operation is supported),
change the dlfeat value back to 0x9.

A new flag FALLOC_FL_WRITE_ZEROES has been introduced in linux for
fallocate which will use the wzds bit in dlfeat to quickly zeroout extents
using unmap operation whenever possible[1].

[1] https://lore.kernel.org/linux-fsdevel/20250619111806.3546162-1-yi.zhang@huaweicloud.com/

Fixes: 146f720c55 ("hw/block/nvme: end-to-end data protection")
Suggested-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Pankaj Raghav <p.raghav@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
---
 hw/nvme/ns.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/hw/nvme/ns.c b/hw/nvme/ns.c
index 38f86a17268f..b0106eaa5c8f 100644
--- a/hw/nvme/ns.c
+++ b/hw/nvme/ns.c
@@ -75,7 +75,7 @@ static int nvme_ns_init(NvmeNamespace *ns, Error **errp)
     ns->csi = NVME_CSI_NVM;
     ns->status = 0x0;
 
-    ns->id_ns.dlfeat = 0x1;
+    ns->id_ns.dlfeat = 0x9;
 
     /* support DULBE and I/O optimization fields */
     id_ns->nsfeat |= (NVME_ID_NS_NSFEAT_DAE | NVME_ID_NS_NSFEAT_OPTPERF_ALL);
-- 
2.53.0