Re: [PATCH] virtio-blk: advertise F_WCE (F_FLUSH) if F_CONFIG_WCE is advertised

[Stefan Hajnoczi]

On Tue, Nov 05, 2019 at 09:22:17PM +0300, Evgeny Yakovlev wrote:
> Virtio spec 1.1 (and earlier), 5.2.5.2 Driver Requirements: Device
> Initialization:
> 
> "Devices SHOULD always offer VIRTIO_BLK_F_FLUSH, and MUST offer it if
> they offer VIRTIO_BLK_F_CONFIG_WCE"
> 
> Currently F_CONFIG_WCE and F_WCE are not connected to each other.
> Qemu will advertise F_CONFIG_WCE if config-wce argument is
> set for virtio-blk device. And F_WCE is advertised only if
> underlying block backend actually has it's caching enabled.
> 
> Fix this by advertising F_WCE if F_CONFIG_WCE is also advertised.
> 
> To preserve backwards compatibility with newer machine types make this
> behaviour governed by "x-enable-wce-if-config-wce" virtio-blk-device
> property and introduce hw_compat_4_2 with new property being off by
> default for all machine types <= 4.2 (but don't introduce 4.3
> machine type itself yet).
> 
> Signed-off-by: Evgeny Yakovlev <address@hidden>
> ---
>  hw/arm/virt.c                  | 1 +
>  hw/block/virtio-blk.c          | 6 +++++-
>  hw/core/machine.c              | 5 +++++
>  hw/i386/pc_piix.c              | 1 +
>  hw/i386/pc_q35.c               | 1 +
>  hw/ppc/spapr.c                 | 2 +-
>  hw/s390x/s390-virtio-ccw.c     | 1 +
>  include/hw/boards.h            | 3 +++
>  include/hw/virtio/virtio-blk.h | 1 +
>  9 files changed, 19 insertions(+), 2 deletions(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

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