Re: [PATCH v2] Shared memory device with interrupt support

From: Avi Kivity <avi@redhat.com>
To: Cam Macdonell <cam@cs.ualberta.ca>
Cc: "kvm@vger.kernel.org list" <kvm@vger.kernel.org>,
	Gregory Haskins <ghaskins@novell.com>
Subject: Re: [PATCH v2] Shared memory device with interrupt support
Date: Mon, 18 May 2009 20:19:18 +0300	[thread overview]
Message-ID: <4A119896.80904@redhat.com> (raw)
In-Reply-To: <4A1191D6.6090105@cs.ualberta.ca>

Cam Macdonell wrote:
>
> My usual noob questions:  Do I need to run Greg's tree on the host for 
> the necessary irqfd/eventfd suppport?  

Yes (though irqfd will be merged real soon, and iosignalfd somewhat 
afterwards).

> Are there any examples to work from aside from Greg's unit tests?

No.

You don't really need to irqfd and iosignalfd to implement all of this, 
they're just optimizations.  You can still pass the eventfds around.  If 
you don't have irqfd, have qemu poll the eventfd, and when something 
happens, inject and interrupt.  Likewise, if you don't have iosignalfd, 
register a pio/mmio handler for the command register, and when they fire 
touch all of the relevant irqfds.  You'll need that anyway for backwards 
compatibility and for level-triggered pci interrupts, which irqfd 
doesn't support.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.