[PATCH 05/15] ARM: Expose PMNC bitfields for KVM use

[Christoffer Dall]

On Tue, Sep 18, 2012 at 9:08 AM, Will Deacon <will.deacon at arm.com> wrote:
> On Sat, Sep 15, 2012 at 04:35:02PM +0100, Christoffer Dall wrote:
>> From: Rusty Russell <rusty.russell at linaro.org>
>>
>> We want some of these for use in KVM, so pull them out of
>> arch/arm/kernel/perf_event_v7.c into their own asm/perf_bits.h.
>>
>> Signed-off-by: Rusty Russell <rusty.russell at linaro.org>
>> Signed-off-by: Christoffer Dall <c.dall at virtualopensystems.com>
>> ---
>>  arch/arm/include/asm/perf_bits.h |   56 ++++++++++++++++++++++++++++++++++++++
>>  arch/arm/kernel/perf_event_v7.c  |   51 +----------------------------------
>>  2 files changed, 57 insertions(+), 50 deletions(-)
>>  create mode 100644 arch/arm/include/asm/perf_bits.h
>
> I don't like this I'm afraid. These bit definitions, although useful for
> kvm, are only applicable to ARMv7 PMUs. Perf does a reasonable job of
> separating the low-level CPU-specific code and adding the v7 definitions
> into their own global header feels like a step backwards. I also want to
> move a load of this into drivers/ at some point and this won't help with
> that effort.
>
> Is KVM just using this for world switch? If so, why does it care about the
> bit definitions (and what do you do for things like debug regs)? Is there
> anything I could add to perf that you could call instead?
>
I'm going to let Rusty reply to this one...

-Christoffer