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SubjectRe: [PATCH] kvm: fast-path msi injection with irqfd
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 <>
> ---
> 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 <>

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