Re: [Xen-devel] [RFC][PATCH 4/6] HVM PCI Passthrough (non-IOMMU)

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 1/6/07 03:45, "Tian, Kevin" <kevin.tian@xxxxxxxxx> wrote:

> My knowledge about 'boot interrupt' issue is related to EOI
> masked RTE entry on some chipset, and not sure the influence of
> polarity change. Then ioapic_acknew may be replaced by this way
> which is more efficient if working. Two times interrupt may be still
> better than EOI-in-end which blocks other pending interrupt, and the
> 2nd interrupt should be quick since only xen internal status is touched.

That's a dubious claim imo. Doubling the rate of interrupts for high-rate
devices is not going to be a performance win, particularly if the interrupts
often require a VMEXIT/VMENTRY round trip. However, ioapic_ack=new is kind
of gross, so if we were confident that high-rate devices were able to use
MSIs, or if I can be convinced that the VT-d approach of re-vectoring the
RTE is robust and applicable to any generic IOAPIC, then I would be quite
happy to kill off ioapic_ack=new.

 -- Keir



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