Re: [PATCH v8 2/4] virtio-blk: add zoned storage emulation for zoned devices

["Matias Bjørling" <m@bjorling.me>]

On 23/03/2023 06.28, Sam Li wrote:
> This patch extends virtio-blk emulation to handle zoned device commands
> by calling the new block layer APIs to perform zoned device I/O on
> behalf of the guest. It supports Report Zone, four zone oparations (open,
> close, finish, reset), and Append Zone.
> 
> The VIRTIO_BLK_F_ZONED feature bit will only be set if the host does
> support zoned block devices. Regular block devices(conventional zones)
> will not be set.
> 
> The guest os can use blktests, fio to test those commands on zoned devices.
> Furthermore, using zonefs to test zone append write is also supported.
> 
> Signed-off-by: Sam Li <faithilikerun@gmail.com>
> ---
>   hw/block/virtio-blk-common.c |   2 +
>   hw/block/virtio-blk.c        | 389 +++++++++++++++++++++++++++++++++++
>   2 files changed, 391 insertions(+)
> 
> diff --git a/hw/block/virtio-blk-common.c b/hw/block/virtio-blk-common.c
> index ac52d7c176..e2f8e2f6da 100644
> --- a/hw/block/virtio-blk-common.c
> +++ b/hw/block/virtio-blk-common.c
> @@ -29,6 +29,8 @@ static const VirtIOFeature feature_sizes[] = {
>        .end = endof(struct virtio_blk_config, discard_sector_alignment)},
>       {.flags = 1ULL << VIRTIO_BLK_F_WRITE_ZEROES,
>        .end = endof(struct virtio_blk_config, write_zeroes_may_unmap)},
> +    {.flags = 1ULL << VIRTIO_BLK_F_ZONED,
> +     .end = endof(struct virtio_blk_config, zoned)},
>       {}
>   };

I used the qemu monitor to expect the state of the devices, and on the 
zoned block device specific entries, the zoned device feature shows up 
in the "unknown-features" field (info virtio-status <device>)

What is missing is an entry in the blk_feature_map structure within 
hw/virtio/virtio-qmp.c. The below fixes it up.

diff --git i/hw/virtio/virtio-qmp.c w/hw/virtio/virtio-qmp.c
index b70148aba9..3efa529bab 100644
--- i/hw/virtio/virtio-qmp.c
+++ w/hw/virtio/virtio-qmp.c
@@ -176,6 +176,8 @@ static const qmp_virtio_feature_map_t 
virtio_blk_feature_map[] = {
              "VIRTIO_BLK_F_DISCARD: Discard command supported"),
      FEATURE_ENTRY(VIRTIO_BLK_F_WRITE_ZEROES, \
              "VIRTIO_BLK_F_WRITE_ZEROES: Write zeroes command supported"),
+    FEATURE_ENTRY(VIRTIO_BLK_F_ZONED, \
+            "VIRTIO_BLK_F_ZONED: Zoned block device"),
  #ifndef VIRTIO_BLK_NO_LEGACY
      FEATURE_ENTRY(VIRTIO_BLK_F_BARRIER, \
              "VIRTIO_BLK_F_BARRIER: Request barriers supported"),

Which then lets qemu report the support like this:

(qemu) info virtio-status /machine/peripheral/virtblk0/virtio-backend
/machine/peripheral/virtblk0/virtio-backend:
   device_name:             virtio-blk
   device_id:               2
   vhost_started:           false
   bus_name:                (null)
   broken:                  false
   disabled:                false
   disable_legacy_check:    false
   started:                 true
   use_started:             true
   start_on_kick:           false
   use_guest_notifier_mask: true
   vm_running:              true
   num_vqs:                 4
   queue_sel:               3
   isr:                     1
   endianness:              little
   status:
         VIRTIO_CONFIG_S_ACKNOWLEDGE: Valid virtio device found,
         VIRTIO_CONFIG_S_DRIVER: Guest OS compatible with device,
         VIRTIO_CONFIG_S_FEATURES_OK: Feature negotiation complete,
         VIRTIO_CONFIG_S_DRIVER_OK: Driver setup and ready
   Guest features:
         VIRTIO_RING_F_EVENT_IDX: Used & avail. event fields enabled,
         VIRTIO_RING_F_INDIRECT_DESC: Indirect descriptors supported,
         VIRTIO_F_VERSION_1: Device compliant for v1 spec (legacy)
         VIRTIO_BLK_F_CONFIG_WCE: Cache writeback and ...,
         VIRTIO_BLK_F_FLUSH: Flush command supported,
         VIRTIO_BLK_F_ZONED: Zoned block device,
         VIRTIO_BLK_F_WRITE_ZEROES: Write zeroes command supported,
         VIRTIO_BLK_F_MQ: Multiqueue supported,
         VIRTIO_BLK_F_TOPOLOGY: Topology information available,
         VIRTIO_BLK_F_BLK_SIZE: Block size of disk available,
         VIRTIO_BLK_F_GEOMETRY: Legacy geometry available,
         VIRTIO_BLK_F_SEG_MAX: Max segments in a request is seg_max
   unknown-features(0x0000010000000000)
   Host features:
         VIRTIO_RING_F_EVENT_IDX: Used & avail. event fields enabled,
         VIRTIO_RING_F_INDIRECT_DESC: Indirect descriptors supported,
         VIRTIO_F_VERSION_1: Device compliant for v1 spec (legacy),
         VIRTIO_F_ANY_LAYOUT: Device accepts arbitrary desc. layouts,
         VIRTIO_F_NOTIFY_ON_EMPTY: Notify when device ...,
         VHOST_USER_F_PROTOCOL_FEATURES: Vhost-user protocol ...,
         VIRTIO_BLK_F_CONFIG_WCE: Cache writeback and w...,
         VIRTIO_BLK_F_FLUSH: Flush command supported,
         VIRTIO_BLK_F_ZONED: Zoned block device,
         VIRTIO_BLK_F_WRITE_ZEROES: Write zeroes command supported,
         VIRTIO_BLK_F_MQ: Multiqueue supported,
         VIRTIO_BLK_F_TOPOLOGY: Topology information available,
         VIRTIO_BLK_F_BLK_SIZE: Block size of disk available,
         VIRTIO_BLK_F_GEOMETRY: Legacy geometry available,
         VIRTIO_BLK_F_SEG_MAX: Max segments in a request is seg_max
   unknown-features(0x0000010000000000)
   Backend features:

Cheers, Matias