Re: [virtio] Re: [virtio-dev] Re: [virtio-comment] Problems with VIRTIO-4 and writeback only disks

[Paolo Bonzini <pbonzini@redhat.com>]

Il 01/10/2013 12:13, Rusty Russell ha scritto:
>>> +Note that buggy legacy devices are common, which always operate in
>>> >> +write back mode even if VIRTIO_BLK_F_WCE isn't accepted, or writeback
>>> >> +is turned off.
>> >
>> > I would remove this paragraph.  You found bugs, true, but it's not that
>> > the affected versions of QEMU are common---they are neither in Debian
>> > nor in RHEL/CentOS, and frankly using anything else in production would
>> > be crazy (also if you do I hope you'll update fast, and those hosts will
>> > not be "common" anymore by the time standardization is finished).
> I was also thinking of this:
> 
> [30] Until version 1.1, QEMU remained in writeback mode even after a
>      guest announced lack of support for VIRTIO_BLK_F_FLUSH.

I would make this even stronger, like "It is undefined whether a disk
operates in writeback or writethrough mode after a guest announces lack
of support for VIRTIO_BLK_F_FLUSH".

Paolo