[Qemu-devel] [PATCH] nvme: support NVME_VOLATILE_WRITE_CACHE feature

[Christoph Hellwig <hch@lst.de>]

The SCSI emulation in the Linux NVMe driver really wants to know
if a device has a volatile write cache.  Given that qemu has moved
away from a model where we report the backing store WCE bit to
one where the WCE bit is supposed to be part of the migratable
guest-visible state we always return 1 here.

Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/hw/block/nvme.c b/hw/block/nvme.c
index 1e07166..50d76f1 100644
--- a/hw/block/nvme.c
+++ b/hw/block/nvme.c
@@ -479,6 +479,9 @@ static uint16_t nvme_get_feature(NvmeCtrl *n, NvmeCmd *cmd, NvmeRequest *req)
         req->cqe.result =
             cpu_to_le32((n->num_queues - 1) | ((n->num_queues - 1) << 16));
         break;
+    case NVME_VOLATILE_WRITE_CACHE:
+        req->cqe.result = cpu_to_le32(1);
+        break;
     default:
         return NVME_INVALID_FIELD | NVME_DNR;
     }