On 2016/1/29 2:06, Will Deacon wrote:

On Thu, Jan 28, 2016 at 04:45:36PM +0000, Marc Zyngier wrote:

quoted

quoted

On 28/01/16 16:31, Andrew Jones wrote:

quoted

quoted

On Wed, Jan 27, 2016 at 11:51:35AM +0800, Shannon Zhao wrote:

quoted

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From: Shannon Zhao <redacted>

When we use tools like perf on host, perf passes the event type and the
id of this event type category to kernel, then kernel will map them to
hardware event number and write this number to PMU PMEVTYPER<n>_EL0
register. When getting the event number in KVM, directly use raw event
type to create a perf_event for it.

Signed-off-by: Shannon Zhao <redacted>
Reviewed-by: Marc Zyngier <redacted>
---
 arch/arm64/include/asm/pmu.h |   3 ++
 arch/arm64/kvm/Makefile      |   1 +
 include/kvm/arm_pmu.h        |  10 ++++
 virt/kvm/arm/pmu.c           | 122 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 136 insertions(+)
 create mode 100644 virt/kvm/arm/pmu.c

diff --git a/arch/arm64/include/asm/pmu.h b/arch/arm64/include/asm/pmu.h
index 4406184..2588f9c 100644
--- a/arch/arm64/include/asm/pmu.h
+++ b/arch/arm64/include/asm/pmu.h

@@ -21,6 +21,7 @@
 
 #define ARMV8_MAX_COUNTERS      32
 #define ARMV8_COUNTER_MASK      (ARMV8_MAX_COUNTERS - 1)
+#define ARMV8_CYCLE_IDX         (ARMV8_MAX_COUNTERS - 1)

I'm not sure we want to add this. It's name is wrong, as it's really
PMCNTENSET_EL0.C, and just a few lines above we have the idx defined
already (ARMV8_IDX_CYCLE_COUNTER), but as zero, because
arch/arm64/kernel/perf_event.c maps it that way.

I think we should do the same with the pmc array, i.e. map the cycle
counter to idx zero.

I tend to have the opposite view. Not for the sake of it, but because I
find it helpful to directly map the code to the architecture
documentation without having to bend another handful of neurons.

Will probably had some good reasons to structure it that way, but I
don't know the rational. Will?

It was years ago, but I suspect that the cycle counter is index zero
because its mandated, whilst the number of event counters is IMPDEF.

So does it need to change the cycle counter index to zero in this patch set?

Thanks,
-- 
Shannon