linux-kernel - Re: [PATCH] kvm: fast-path msi injection with irqfd

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Date:	Fri, 19 Nov 2010 09:23:07 -0700
From:	"Gregory Haskins" <ghaskins@...ell.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>,
	"Marcelo Tosatti" <mtosatti@...hat.com>
Cc:	"Xiao Guangrong" <xiaoguangrong@...fujitsu.com>,
	"Avi Kivity" <avi@...hat.com>,
	"Chris Lalancette" <clalance@...hat.com>,
	"Gleb Natapov" <gleb@...hat.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kvm: fast-path msi injection with irqfd

>>> On 11/19/2010 at 10:54 AM, in message <20101119155427.GA20279@....cnet>,
Marcelo Tosatti <mtosatti@...hat.com> wrote: 
> On Thu, Nov 18, 2010 at 07:09:08PM +0200, Michael S. Tsirkin wrote:
>> Store irq routing table pointer in the irqfd object,
>> and use that to inject MSI directly without bouncing out to
>> a kernel thread.
>> 
>> While we touch this structure, rearrange irqfd fields to make fastpath
>> better packed for better cache utilization.
>> 
>> This also adds some comments about locking rules and rcu usage in code.
>> 
>> Some notes on the design:
>> - Use pointer into the rt instead of copying an entry,
>>   to make it possible to use rcu, thus side-stepping
>>   locking complexities.  We also save some memory this way.
>> - Old workqueue code is still used for level irqs.
>>   I don't think we DTRT with level anyway, however,
>>   it seems easier to keep the code around as
>>   it has been thought through and debugged, and fix level later than
>>   rip out and re-instate it later.
>> 
>> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>> ---
>> 
>> OK, this seems to work fine for me. Tested with virtio-net in guest
>> with and without vhost-net.  Pls review/apply if appropriate.
> 
> Acked-by: Marcelo Tosatti <mtosatti@...hat.com>

Acked-by: Gregory Haskins <ghaskins@...ell.com>



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