On Thu, Sep 06, 2012 at 06:16:03PM +0100, Marc Zyngier wrote:
> Add minimal guest support to perf, so it can distinguish whether
> the PMU interrupt was in the host or the guest, as well as collecting
> some very basic information (guest PC, user vs kernel mode).
>
> This is not feature complete though, as it doesn't support backtracing
> in the guest.
>
> Based on the x86 implementation, tested with KVM/ARM.
>
> Cc: Will Deacon <will.deacon@xxxxxxx>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/include/asm/perf_event.h | 7 ++++++-
> arch/arm/kernel/perf_event.c | 36 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 42 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/include/asm/perf_event.h b/arch/arm/include/asm/perf_event.h
> index e074948..77537bb 100644
> --- a/arch/arm/include/asm/perf_event.h
> +++ b/arch/arm/include/asm/perf_event.h
> @@ -12,6 +12,11 @@
> #ifndef __ARM_PERF_EVENT_H__
> #define __ARM_PERF_EVENT_H__
>
> -/* Nothing to see here... */
> +/* Not much to see here... */
You can just remove this silly comment :)
> +struct pt_regs;
> +extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
> +extern unsigned long perf_misc_flags(struct pt_regs *regs);
> +#define perf_misc_flags(regs) perf_misc_flags(regs)
>
> #endif /* __ARM_PERF_EVENT_H__ */
> diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c
> index ab243b8..8836425 100644
> --- a/arch/arm/kernel/perf_event.c
> +++ b/arch/arm/kernel/perf_event.c
> @@ -817,6 +817,10 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs)
> {
> struct frame_tail __user *tail;
>
> + if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
> + /* TODO: We don't support guest os callchain now */
> + return;
> + }
>
> tail = (struct frame_tail __user *)regs->ARM_fp - 1;
>
> @@ -844,9 +848,41 @@ perf_callchain_kernel(struct perf_callchain_entry *entry, struct pt_regs *regs)
> {
> struct stackframe fr;
>
> + if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
> + /* TODO: We don't support guest os callchain now */
> + return;
> + }
> +
Will we ever support this? It sounds incredibly difficult -- how can you
walk the guest stack without things disappearing under your feet?
> +unsigned long perf_instruction_pointer(struct pt_regs *regs)
> +{
> + if (perf_guest_cbs && perf_guest_cbs->is_in_guest())
> + return perf_guest_cbs->get_guest_ip();
> +
> + return instruction_pointer(regs);
> +}
> +
> +unsigned long perf_misc_flags(struct pt_regs *regs)
> +{
> + int misc = 0;
> +
> + if (perf_guest_cbs && perf_guest_cbs->is_in_guest()) {
> + if (perf_guest_cbs->is_user_mode())
> + misc |= PERF_RECORD_MISC_GUEST_USER;
> + else
> + misc |= PERF_RECORD_MISC_GUEST_KERNEL;
> + } else {
> + if (user_mode(regs))
> + misc |= PERF_RECORD_MISC_USER;
> + else
> + misc |= PERF_RECORD_MISC_KERNEL;
> + }
> +
> + return misc;
> +}
Hmm, both of these look like they should be made generic but I see that x86
and ppc do have some differences, so I guess we should have our own copies
for the time being...
Will
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