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Date: Tue, 26 Jan 2010 10:43:04 -0200
From: Marcelo Tosatti <mtosatti@redhat.com>
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Subject: [Qemu-devel] Re: [PATCH v3][uqmaster] kvm: Flush coalesced MMIO
	buffer periodly
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To: Sheng Yang <sheng@linux.intel.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org, Avi Kivity <avi@redhat.com>, Alexander Graf <agraf@suse.de>

On Tue, Jan 26, 2010 at 07:21:16PM +0800, Sheng Yang wrote:
> The default action of coalesced MMIO is, cache the writing in buffer, until:
> 1. The buffer is full.
> 2. Or the exit to QEmu due to other reasons.
> 
> But this would result in a very late writing in some condition.
> 1. The each time write to MMIO content is small.
> 2. The writing interval is big.
> 3. No need for input or accessing other devices frequently.
> 
> This issue was observed in a experimental embbed system. The test image
> simply print "test" every 1 seconds. The output in QEmu meets expectation,
> but the output in KVM is delayed for seconds.
> 
> Per Avi's suggestion, I hooked flushing coalesced MMIO buffer in VGA update
> handler. By this way, We don't need vcpu explicit exit to QEmu to
> handle this issue.
> 
> Signed-off-by: Sheng Yang <sheng@linux.intel.com>

Applied, thanks.