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virtio-blk: advertise F_WCE (F_FLUSH) if F_CONFIG_WCE is advertised

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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 <wrfsh@yandex-team.ru>
Message-Id: <1572978137-189218-1-git-send-email-wrfsh@yandex-team.ru>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Evgeny Yakovlev 2019-11-05 21:22:17 +03:00 • committed by Stefan Hajnoczi
parent b0ca999a43
commit 5f2585772f
9 changed files with 19 additions and 2 deletions
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3
include/hw/boards.h
View file

@ -329,6 +329,9 @@ struct MachineState {
} \
type_init(machine_initfn##_register_types)
extern GlobalProperty hw_compat_4_2[];
extern const size_t hw_compat_4_2_len;
extern GlobalProperty hw_compat_4_1[];
extern const size_t hw_compat_4_1_len;