RE: [Xen-devel] IRQ SMP affinity problems in domU with vcpus > 4 on HP ProLiant G6 with dual Xeon 5540 (Nehalem)

["Cinco, Dante" <Dante.Cinco@xxxxxxx>]

With vcpus < 4, logical flat mode works fine (no error message). I can change 
smp_affinity to any value > 0 and < 16 and the interrupts go to the proper 
CPU(s). Could you point me to the code that handles MSI so that I can better 
understand the MSI implementation?

Thanks.

Dante
________________________________________
From: Qing He [qing.he@xxxxxxxxx]
Sent: Saturday, October 10, 2009 2:43 AM
To: Cinco, Dante
Cc: Keir Fraser; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] IRQ SMP affinity problems in domU with vcpus > 4       
on HP ProLiant G6 with dual Xeon 5540 (Nehalem)

On Sat, 2009-10-10 at 07:39 +0800, Cinco, Dante wrote:
> When I tried adding "hvm_debug=0x200" in the Xen command line, the domU
> became unaccessible on boot up with the Xen console constantly printing
> this message: "(XEN) [HVM:1.0] <vioapic_irq_positive_edge> irq 2."

So this is useless, maybe one time setups should be split out from
those fire everytime, or using a separate debug level for MSI operation.

> Change /proc/irq/48/smp_affinity from 1 to 2
> - Xen console: (XEN) do_IRQ: 8.211 No irq handler for vector (irq -1)

This is weird, although there is no other confirmation, I guess this
vector 211 (0xd3) is the MSI vector. This can explain why the MSI
doesn't fire any more.

However, this error message is not expected. Physical MSI at xen
level always goes to vcpu 0 when it's first bound, and the affinity
doesn't change after this. Futhermore, logical flat mode works fine,
do you observe this error message when vcpus=4?

I'll continue to investigate and try to reproduce the problem at
my side.

Thanks,
Qing

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