Re: xhci passthrough

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Oct 28, 2010 at 12:01:18AM +0200, Sander Eikelenboom wrote:
> Hi Konrad,
> 
> Due to a 2.6.37-merge-window kernel now being able to boot under Xen i was able to test my xhci controller under dom0 which i previously couldn't.
> 
> The results:
> A) 2.6.37-merge-window kernel baremetal: Videograbbing while doing 20 iterations of make -j6 of kernel works.
> B) Xen + 2.6.37-merge-window kernel as Dom0: Videograbbing while doing 20 iterations of make -j6 of kernel works.

Great!
> C) Xen + 2.6.32.24 pvops dom0 +  2.6.37-merge-window kernel DomU: Videograbbing while doing 20 iterations of make -j6  still freezes the machine without a trace after a short while.

Ok, so it points to the 2.6.32.24 doing something funky, which unfortunatly  does not help that much
as the xen patches that are in the 2.6.37-merge-window for IRQ are about the same
as what 2.6.32.24 has. Thought the 2.6.37-merge-window got tons of bells and whistles in the
generic Linux kernel code part.

These interrupts were for the MSI-X for the XHCI controller or was it legacy interrupts?

> 
> An other interesting thing is the interrupt rate i see in /proc/interrrupts for the xhci controller, i measured for 5 minutes each time.
> In situation:
> A) About 3200 Interrupts/second
> B) About 3200 Interrupts/second
> C) About 7800 Interrupts/second, what would be 7.8 interrupt per ms which seems to work as long as you don't stress the rest to the limit.
>    Which probably causes some sort of deadlock (some where in the path from device, xen, dom0/pciback , domU/pcifront, xhci driver, application.) when not delivered on time or when it boldly goes on a code path where no one has gone before ..
> 
> Compared with a measurement of interrupts by a USB2 controller:
> Around 155 Interrupts/second
> 
> Probably a silly question without a right answer ... but what interrupt rate would you guess it should be able to take ?
> And is it logically that when passed through it causes around 2.5 times more interrupts ?
> 
> Now testing on a Intel(R) Core(TM)2 Quad CPU    Q9400  @ 2.66GHz
> 
> --
> 
> Sander
> 
> 
> 
> 
> 
> 
> 
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