Re: [Qemu-devel] [PATCH 2/2] virtio-blk: disable write cache if not negotiated

[Kevin Wolf]

Am 04.07.2012 14:21, schrieb Paolo Bonzini:
> Il 04/07/2012 12:16, Kevin Wolf ha scritto:
>>>> Yes.  It doesn't override cache=unsafe though.
>> When the guest doesn't support flushes, cache=writeback is equivalent to
>> cache=unsafe, so if you want the old behaviour back you can switch to
>> cache=unsafe without additional risks.
>>
>> We don't have a cache=directunsafe, though, so if you want to get the
>> old behaviour of cache=none back, you're out of luck. Not sure how
>> acceptable this is.
> 
> If we want to fix this, let's take the occasion to split the parameters
> into cache=on/off (well, we have that already), flush=on/off, and a
> device-side wce=on/off.

You're volunteering? Great! ;-)

>> Irrespective of this concern I've come to the conclusion that I agree
>> and we actually must enforce this for non-unsafe mode, and not doing it
>> is a bug.
> 
> Thanks!  Is that an Acked-by/Reviewed-by? :)

Before merging the patches (or actually this patch, I think patch 1 is
fairly independent), I'd like to hear more opinions on whether we need
the cache parameter split first. But as far as the hardware is
concerned, sure, take it as an Acked-by and go forward with the spec and
kernel side of things.

Kevin