Re: [Xen-devel] [BUG] hhvm running on Ubuntu 13.04 with Xen Hypervisor - linux kernel panic

[Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>]

Am Freitag 20 September 2013, 12:07:00 schrieb Craig Carnell:
> Unfortunately the servers are provided "as is" by rackspace unless this is
> something I can change in the terminal (unlikely).
> 
> Is there any performance loss from not using hardware performance
> counters?

I don't know hhvm and so I don't know for what the counters are used in
this case.
Normally linux uses 1 counter for watchdog handling. If the counters
are not usable the watchdog handling switches to the timer interrupt I think.
The other use case is the perf command.

Another attempt would be to patch the native_read_pmc() function with
a dummy returning always 0 and  see what happens.

> Also, do you know the configure command as it did not recognise
> it when I tried.

No unfortunately not :-(

Dietmar.

> 
> Thanks
> 
> On 20/09/2013 13:02, "Dietmar Hahn" <dietmar.hahn@xxxxxxxxxxxxxx> wrote:
> 
> >Am Donnerstag 19 September 2013, 15:02:38 schrieb Craig Carnell:
> >> Xen Version is 4.1.3
> >> 
> >> I'm not able to run xm it asks for xen-utils 4.1 which I install
> >>(xen-utils 4.2 installs) but it can't find it..
> >> 
> >> Sorry!
> >
> >As it seems your hhvm is running as PV domu with cpl=3 and in this case
> >the
> >rdpmc leads to the general protection fault because there is no VPMU
> >support
> >for PV domains.
> >What you can do is let your hhvm run as a HVM domain. Then you should not
> >get a panic.
> >The other way is to build your hhvm without hardware performance counters
> >like Wei Liu already mentioned. This is the way for linux dom0 I think.

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