[RFC PATCH 1/1] powerpc/ftrace: Exclude real mode code from

Naveen N. Rao naveen.n.rao at linux.vnet.ibm.com
Fri Mar 9 19:17:38 AEDT 2018

Steven Rostedt wrote:
> On Thu, 08 Mar 2018 00:07:07 +0530
> "Naveen N. Rao" <naveen.n.rao at linux.vnet.ibm.com> wrote:
>> Yes, that's negligible.
>> Though, to be honest, I will have to introduce a 'mfmsr' for the older 
>> -pg variant. I still think that the improved reliability far outweighs 
>> the minor slowdown there.
> In that case, can you introduce a read_mostly variable that can be
> tested before calling the mfmsr. Why punish normal ftrace tracing if
> kvm is not enabled or running?
> Both should probably have an #ifdef CONFIG_KVM encapsulating the code.

Agreed. My previous intent was to exclude all realmode code from ftrace, 
but I now think it is better to only exclude the KVM path. So, I will 
make it specific to KVM.

- Naveen

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