[Rust-VMM] [Rust-vmm] Goals for this list

Boeuf, Sebastien sebastien.boeuf at intel.com
Tue Feb 26 14:39:35 UTC 2019

On Tue, 2019-02-26 at 12:38 +0100, Paolo Bonzini wrote:
> On 26/02/19 10:09, Dr. David Alan Gilbert wrote:
> > > But if we can find some mechanisms to communicate the MSI vectors
> > > chosen by the guest kernel down to the hypervisor about a device,
> > > we could definitely get rid of IOAPIC, hence reaching the end
> > > goal
> > > I'm talking about here. Just note that ACPI would be a good way
> > > for
> > > the guest to communicate those information with the VMM.
> > 
> > Would a new ACPI mechanism really be any easy than some really
> > basic 
> > PCI?  You don't really need to provide a true PCI hierarchy or
> > anything.
> Yeah, I don't see the problem with configuring MSI via the PCI
> configuration space.  Being able to use MSI is just one more reason
> to
> drop virtio-mmio and switch to virtio-pci.

Yes you're right, and if you go all the way with PCI, you solve a lot
of issues.
But let's say you don't have PCI support, you need a way to notify your
guest about things like hotplug, and you do so using a GED or GPE ACPI
device. In that case, we still want to get rid of the IOAPIC dependency
and make sure those ACPI devices would support MSI.

> (Without IOAPIC, the PCI devices would not be able to serve INTX
> interrupts, but that's not a problem for most modern devices).

Yes but that's not a problem if you consider using only modern devices.

> Paolo

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