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

["Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>]

Keir Fraser <mailto:keir.fraser@xxxxxxxxxxxxx> wrote:
> 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?

I usuually do experiement in linux kernel, and it 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? 

I haven't change anything at all, the machine is on lab, which is far
away from my cub.  And I just stay at home at weekend.

> 
> -- Keir

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