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Date: Wed, 21 Nov 2018 13:39:23 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20181121053923.GA31447@magic>
References: <afa43fbb-98e0-f6e7-0d41-e7005501e256@oracle.com>
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Subject: Re: [Qemu-devel] When AioHandler->is_external=true?
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To: Dongli Zhang <dongli.zhang@oracle.com>
Cc: Qemu-block <qemu-block@nongnu.org>, qemu-devel@nongnu.org

On Tue, 11/20 20:34, Dongli Zhang wrote:
> Hi,
> 
> Would you please help explain in which case AioHandler->is_external is true, and
> when it is false?
> 
> I read about iothread and mainloop and I am little bit confused about it.

VirtIO's ioeventfd is an example of is_external == true. It means the events
handler on this fd may initiate more I/O, such as read/write on virtual storage
backend, so are specially taken care of at certain points when we won't want
more I/O requests to be processed, such as when a block job is completing, or in
the middle of a QMP transaction.

Fam