Re: gnumach: IOAPIC and LAPIC support

[Samuel Thibault]

Damien Zammit, le ven. 26 mars 2021 21:10:00 +1100, a ecrit:
> On 26/3/21 8:59 pm, Samuel Thibault wrote:
> > Damien Zammit, le ven. 26 mars 2021 20:48:45 +1100, a ecrit:
> >> As discussed, this should be done via a new pci-arbiter RPC that
> >> requests the IRQ id for a particular device.
> > 
> > Mmm, AIUI a driver can already read the PCI IRQ information with
> > pci_conf_read, and lookup in acpi for the irq line, I don't think
> > pci-arbiter itself needs an additional RPC? That could rather be on the
> > acpi server.
> 
> As I understand it, the PCI IRQ information is incorrect in the config space,

"incorrect", or "incomplete"? According to below, I guess the former.

> the only way to know the APIC pin for a specific device is via ACPI.
> So you have to pass in the B/D/F of the device to an acpi RPC and discover 
> its pin.

Ah, so the PCI IRQ information is just completely useless?

> Why should every user of a pci device have specific logic to discover its pin?
> Wouldn't this be better to be centralised in a pci RPC?

Yes but it could as well be an ACPI RPC. Rump would get the B/D/F PCI
information from pci-arbiter, and then ask acpi for the actual IRQ to
use for that B/D/F triplet. pci-arbiter itself doesn't know better than
acpi.

Samuel