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From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Subject: Re: [PATCH v8 3/8] vhost: vring queue setup for multiple
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Date: Tue, 27 Oct 2015 17:53:20 +0800
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On Tue, Oct 27, 2015 at 11:42:24AM +0200, Michael S. Tsirkin wrote:
...
> > > Looking at that, at least when MQ is enabled, please don't key
> > > stopping queues off GET_VRING_BASE.
> > 
> > Yes, that's only a workaround. I guess it has been there for quite a
> > while, maybe at the time qemu doesn't send RESET_OWNER message.
> 
> RESET_OWNER was a bad idea since it basically closes
> everything.
> 
> > > There are ENABLE/DISABLE messages for that.
> > 
> > That's something new,
> 
> That's part of multiqueue support. If you ignore them,
> nothing works properly.

I will handle them shortly. (well, it may still need weeks :(

> > though I have plan to use them instead, we still
> > need to make sure our code work with old qemu, without ENABLE/DISABLE
> > messages.
> 
> OK but don't rely on this for new code.

Yes.

> 
> > And I will think more while enabling live migration: I should have
> > more time to address issues like this at that time.
> > 
> > > Generally guys, don't take whatever QEMU happens to do for
> > > granted! Look at the protocol spec under doc/specs directory,
> > > if you are making more assumptions you must document them!
> > 
> > Indeed. And we will try to address them bit by bit in future.
> > 
> > 	--yliu
> 
> But don't pile up these workarounds meanwhile.  I'm very worried.  The
> way you are carrying on, each new QEMU is likely to break your
> assumptions.

Good point. I'll have more discussion with Huawei, to see if we can
fix them sooner.

	--yliu