Re: [virtio-dev] On doorbells (queue notifications)

[Stefan Hajnoczi <stefanha@redhat.com>]

On Tue, Jul 14, 2020 at 10:43:36PM +0100, Alex Bennée wrote:
> I'm slightly confused by the MSI terminology because this only seems to
> be relevant for the PCI legacy interface and AFAICT only touch the
> outgoing path in setup and del_vq. Do incoming MSI interrupts just get
> mapped directly to the appropriate handler function to process the
> queues or the config?

When MSI is used the VIRTIO ISR register does not need to be read by the
guest interrupt handler.

> Finally I'm curious if this is just a problem avoided by the s390
> channel approach? Does the use of messages over a channel just avoid the
> sort of bouncing back and forth that other hypervisors have to do when
> emulating a device?

What does "bouncing back and forth" mean exactly?

Stefan

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