Re: [Qemu-block] [PATCH v6 0/4] virtio/block: handle zoned backing devices

[Stefan Hajnoczi]

On Wed, Sep 04, 2019 at 05:00:56PM -0400, Dmitry Fomichev wrote:
> Currently, attaching zoned block devices (i.e., storage devices
> compliant to ZAC/ZBC standards) using several virtio methods doesn't
> work properly as zoned devices appear as regular block devices at the
> guest. This may cause unexpected i/o errors and, potentially, some
> data corruption.
> 
> To be more precise, attaching a zoned device via virtio-pci-blk,
> virtio-scsi-pci/scsi-disk or virtio-scsi-pci/scsi-hd demonstrates the
> above behavior. The virtio-scsi-pci/scsi-block method works with a
> recent patch. The virtio-scsi-pci/scsi-generic method also appears to
> handle zoned devices without problems.
> 
> This patch set adds code to check if the backing device that is being
> opened is a zoned Host Managed device. If this is the case, the patch
> prohibits attaching such device for all use cases lacking proper
> zoned support.
> 
> Host Aware zoned block devices are designed to work as regular block
> devices at a guest system that does not support ZBD. Therefore, this
> patch set doesn't prohibit attachment of Host Aware devices.
> 
> Considering that there is still a couple of different working ways
> to attach a ZBD, this patch set provides a reasonable short-term
> solution for this problem.
> 
> ZBD support for virtio-scsi-pci/scsi-disk and virtio-scsi-pci/scsi-hd
> does not seem as necessary. Users will be expected to attach zoned
> block devices via virtio-scsi-pci/scsi-block instead.
> 
> This patch set contains some Linux-specific code. This code is
> necessary to obtain Zoned Block Device model value from Linux sysfs.
> 
> History:
> 
> v1 -> v2:
> - rework code to be permission-based
> - always allow Host Aware devices to be attached
> - add fix for Host Aware attachments aka RCAP output snoop
> 
> v2 -> v3:
> - drop the patch for RCAP output snoop - merged separately
> 
> v3 -> v4:
> - rebase to the current code
> 
> v4 -> v5:
> - avoid checkpatch warning
> 
> v5 -> v6:
> - address review comments from Stefan Hajnoczi
> 
> Dmitry Fomichev (4):
>   block: Add zoned device model property
>   raw: Recognize zoned backing devices
>   block/ide/scsi: Set BLK_PERM_SUPPORT_HM_ZONED
>   raw: Don't open ZBDs if backend can't handle them
> 
>  block.c                   | 15 +++++++
>  block/file-posix.c        | 89 +++++++++++++++++++++++++++++++++------
>  block/io.c                |  5 +++
>  hw/block/block.c          |  8 +++-
>  hw/block/fdc.c            |  5 ++-
>  hw/block/nvme.c           |  2 +-
>  hw/block/virtio-blk.c     |  2 +-
>  hw/block/xen-block.c      |  2 +-
>  hw/ide/qdev.c             |  2 +-
>  hw/scsi/scsi-disk.c       | 13 +++---
>  hw/scsi/scsi-generic.c    |  2 +-
>  hw/usb/dev-storage.c      |  2 +-
>  include/block/block.h     | 19 ++++++++-
>  include/block/block_int.h |  3 ++
>  include/hw/block/block.h  |  3 +-
>  15 files changed, 141 insertions(+), 31 deletions(-)
> 
> -- 
> 2.21.0
> 

Reviewed-by: Stefan Hajnoczi <address@hidden>

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