[PATCH] PPC: Don't sync timebase when inside VM

[Alexander Graf]

On 02.03.2012, at 17:20, Scott Wood wrote:

> On Fri, Mar 02, 2012 at 03:12:33PM +0100, Alexander Graf wrote:
>> When running inside a virtual machine, we can not modify timebase, so
>> let's just not call the functions for it then.
>> 
>> This resolves hangs when booting e500 SMP guests on overcommitted hosts.
>> 
>> Reported-by: Stuart Yoder <B08248 at freescale.com>
>> Signed-off-by: Alexander Graf <agraf at suse.de>
>> ---
>> arch/powerpc/platforms/85xx/smp.c |    7 +++++++
>> 1 files changed, 7 insertions(+), 0 deletions(-)
>> 
>> diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
>> index ff42490..d4b6c1f 100644
>> --- a/arch/powerpc/platforms/85xx/smp.c
>> +++ b/arch/powerpc/platforms/85xx/smp.c
>> @@ -249,6 +249,13 @@ void __init mpc85xx_smp_init(void)
>> 		smp_85xx_ops.cause_ipi = doorbell_cause_ipi;
>> 	}
>> 
>> +	/* When running under a hypervisor, we can not modify tb */
>> +	np = of_find_node_by_path("/hypervisor");
>> +	if (np) {
>> +		smp_85xx_ops.give_timebase = NULL;
>> +		smp_85xx_ops.take_timebase = NULL;
>> +	}
>> +
>> 	smp_ops = &smp_85xx_ops;
> 
> Again, for 85xx we should *never* sync the timebase in the kernel,
> hypervisor or no.

The code says "if the kexec config option is enabled, do the sync". I'm fairly sure it's there for a reason.

Git blame points to the following commit:

commit f933a41e419a954ef90605224e02c3ded78f3372
Author: Matthew McClintock <msm at freescale.com>
Date:   Wed Jul 21 16:14:53 2010 -0500

    powerpc/85xx: kexec for SMP 85xx BookE systems
    
    Adds support for kexec on 85xx machines for the BookE platform.
    Including support for SMP machines
    
    Based off work from Maxim Uvarov <muvarov at mvista.com>
    Signed-off-by: Matthew McClintock <msm at freescale.com>
    Signed-off-by: Kumar Gala <galak at kernel.crashing.org>


Alex