[Xen-devel] xen dependant on pcpu 0 ?

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Hi Keir,

Does xen and/or the xen console depend on physical cpu 0 ?

I'm still trying to solve the mystery of my machine freezing when doing:

 - videograbbing in a domU with a usb3 pci-express controller passed through 
(seems to cause quite a few interrupts)
 - compiling a linux kernel with "make -j 6"

It's a 6 core AMD phenom x6.

Without cpu pinning:
I can freeze the machine easily within a minute after starting the compile, at 
first xen serial console also slows down under the load (slow updates).
When the machine freezes i can't do anything with xen serial console.

With cpu pinning:
By not using the pcpu 0 at all for any domain, and pinning the domain with the 
videograbber to it's own pcpu (pcpu 5)  it seems the machine keeps running 
after 20 "make -j6" iterations of kernel compilation.
Xen serial console stays responsive and doesn't slow down during the kernel 
compilation. The videograbber shows no problem grabbing video.


Name                                ID  VCPU   CPU State   Time(s) CPU Affinity
Domain-0                             0     0     3   r--    2169.7 1-4
Domain-0                             0     1     1   -b-    2339.3 1-4
Domain-0                             0     2     2   -b-    2358.9 1-4
Domain-0                             0     3     3   -b-    2298.2 1-4
Domain-0                             0     4     1   -b-    2221.9 1-4
Domain-0                             0     5     4   -b-    2287.7 1-4
backup                               9     0     4   -b-      10.6 1-4
database                             1     0     4   -b-      45.3 1-4
davical                              5     0     3   -b-       8.7 1-4
git                                  8     0     2   -b-       7.9 1-4
mail                                 2     0     4   -b-       8.0 1-4
samba                                3     0     3   -b-      11.1 1-4
security                             7     0     5   r--    1433.2 5
www                                  4     0     1   -b-      10.2 1-4
zabbix                               6     0     3   -b-      21.2 1-4


Is there a way a deadlock could occur between hypervisor <-> dom0 <-> domU 
especially related to passthrough/interrupts in the context of pcpu 0 ?

--
Sander


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