Re: [Xen-devel] [PATCH 0/5] Add MSI support to XEN

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 31/3/08 14:57, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> Keir, when I try to get the ip address today, I suddenly found I can't
> reproduce it anymore, also orginally if I removed the code that trigger
> the software LSC interrupt, the NIC can still work and get IP address,
> but now if I remove that code, the NIC can't work anymore.
> It is really strange to me, I did't change anything to the system. Also
> I don't know any changes in the lab environment that may cause this
> change. But I do can reproduce it before each time.
> 
> Really frustrated to get this :-( , do you think we still need move the
> config space access down, now the only reasons to move this down is,
> ack_edge_ioapic_irq() did the mask, and this mask can make HV more
> robust.

So, if you leave the driver as it is (triggering the software LSC
interrupt), do APIC EOI in Xen before executing the interrupt handler in
dom0, and do not mask the MSI at all, then you no longer hang?

That's a weird change in behaviour if so!

I wonder whether there is a timing issue of some sort, and it depends if the
NIC generates the software-triggered interrupt at a fast enough rate that
the host CPU fails to make progress if it doesn't mask the MSI? You haven't
changed test machine at all, or put the NIC in a different PCI slot, or
anything like that?

 -- Keir



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