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Date: Mon, 06 May 2013 16:28:43 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v7 0/7] push mmio dispatch out of big lock
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To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: qemu-devel <qemu-devel@nongnu.org>, Liu Ping Fan <qemulist@gmail.com>

Il 06/05/2013 16:05, Jan Kiszka ha scritto:
>> Also, memory_region_find cannot know if it's returning a valid result,
>> and the callee cannot check it because the region may have disappeared
>> already when it is returned.
> 
> Again, we hold the address space lock while checking the conditions. If
> a region does not supports BQL-free mode and BQL is not held, we have an
> error and return NULL (or bail out with a runtime error).

I've now posted my patches (which are really complementary to Ping
Fan's), and there's no address space lock.  (here is a lock, but the
critical section is literally a handful of instructions and everything
is done with reference counting.

Paolo