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Re: [Qemu-devel] plan for device assignment upstream
From: |
Avi Kivity |
Subject: |
Re: [Qemu-devel] plan for device assignment upstream |
Date: |
Mon, 02 Jul 2012 12:43:48 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120605 Thunderbird/13.0 |
On 07/02/2012 12:30 PM, Jan Kiszka wrote:
> On 2012-07-02 11:18, Michael S. Tsirkin wrote:
>> I've been thinking hard about Jan's patches for device
>> assignment. Basically while I thought it makes sense
>> to make all devices: assignment and not - behave the
>> same and use same APIs for injecting irqs, Anthony thinks there is huge
>> value in making irq propagation hierarchical and device assignment
>> should be special cased.
>
> On the long term, we will need direct injection, ie. caching, to allow
> making it lock-less. Stepping through all intermediate layers will cause
> troubles, at least performance-wise, when having to take and drop a lock
> at each stop.
So we precalculate everything beforehand. Instead of each qemu_irq
triggering a callback, calculating the next hop and firing the next
qemu_irq, configure each qemu_irq array with a function that describes
how to take the next hop. Whenever the configuration changes,
recalculate all routes.
For device assignment or vhost, we can have a qemu_irq_irqfd() which
converts a qemu_irq to an eventfd. If the route calculations determine
that it can be serviced via a real irqfd, they also configure it as an
irqfd. Otherwise qemu configures a poll on this eventfd and calls the
callback when needed.
--
error compiling committee.c: too many arguments to function
- [Qemu-devel] plan for device assignment upstream, Michael S. Tsirkin, 2012/07/02
- Re: [Qemu-devel] plan for device assignment upstream, Avi Kivity, 2012/07/02
- Re: [Qemu-devel] plan for device assignment upstream, Jan Kiszka, 2012/07/02
- Re: [Qemu-devel] plan for device assignment upstream,
Avi Kivity <=
- Re: [Qemu-devel] plan for device assignment upstream, Michael S. Tsirkin, 2012/07/04
- Re: [Qemu-devel] plan for device assignment upstream, Avi Kivity, 2012/07/04
- Re: [Qemu-devel] plan for device assignment upstream, Michael S. Tsirkin, 2012/07/04