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Date: Fri, 13 Nov 2009 03:00:03 +0000
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Re: [PATCH] qemu/virtio: make wmb compiler barrier +
	comments
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References: <20091026131715.GA25271@redhat.com>
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To: Scott Tsai <scottt.tw@gmail.com>
Cc: qemu-devel@nongnu.org, Paul Brook <paul@codesourcery.com>, "Michael S. Tsirkin" <mst@redhat.com>

Scott Tsai wrote:
> I do have a newbie question, when exactly would vrtio have to handle
> concurrent access from multiple threads?
> My current reading of the code suggests:
> 1. when CONFIG_IOTHREAD is true
> 2. when CONFIG_KVM is true and the guest machine has multiple CPUs

It's enough to have CONFIG_KVM with a single guest CPU, isn't it?

Because the guest CPU can still run concurrently with the I/O thread
on kvm, and the host may have multiple CPUs even though the guest does
not.

-- Jamie