Re: [Xen-devel] [PATCH 1/5] Add MSI support to XEN

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 28/3/08 09:23, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> I think the reverse. :-) Here IRQ is just a namespace which is allocatable
> and not bound to platform hard-wired logic. Each MSI just requires one
> IRQ placeholder to gear to evtchn core with the latter on top of IRQ name-
> space. However GSI or ISA IRQ more indicates platform attribute which
> doesn't fit the purpose here, though GSI can be also tweaked in some
> version of Linux kernel.

I don't understand you. Do you mean *PIRQ* is just a namespace which is
allocatable? I fully agree with that. I was talking about the
MAO_IRQ_TYPE_IRQ binding type -- here I believe 'IRQ' does refer to a real
platform resource, but 'IRQ' is not a well-defined architectural namespace
like 'GSI' or 'ISA IRQ'. So the interface should be fixed imo.

> This should work, and may solve the issue Yunhong described in
> another mail by giving Xen ability to mask device directly upon
> spurious interrupts. And... seems like less change to Linux code?
> The only concern is how complex the interface may finally go,
> and in this case Xen still needs to sync PCI config space access
> for port I/O style.

Yes, the synchronisation is pretty easy though. We just have to add a layer
of emulation to PV guest accesses to 0xcf8/0xcfc.

 -- Keir



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