[RFC PATCH 0/3] coresight: Support exclude_guest with Feat_TRF and nVHE

[James Clark]

Hi,

I'm looking for help in testing this and for feedback on whether it's
useful to anyone. Testing it requires hardware that has Feat_TRF (v8.4)
but no TRBE. This is because TRBE usage is disabled in nVHE guests.

I don't currently have any access to any hardware, and the FVP model
can only do self hosted trace using TRBE.

Currently with nVHE you would always get trace from guests, and
filtering out isn't possible without this patchset. In comparison, with
VHE guests, they never generate guest trace without [1]. I think the
existence of trace rather than lack of could suggest that this change is
less useful than [1]. Also the restricted set of hardware that it works
on supports that too. 

Apart from compilation and checking that the exclude guest settings
are correctly programmed on guest switch, this is untested by me.

Applies to kvmarm/next (3b4e3afb2032)

[1]: https://lore.kernel.org/linux-arm-kernel/20230804085219.260790-3-james.clark@arm.com/

James Clark (3):
  arm64: KVM: Add support for exclude_guest and exclude_host for ETM
  arm64: KVM: Support exclude_guest for Coresight trace in nVHE
  coresight: Support exclude_guest with Feat_TRF and nVHE

 arch/arm64/include/asm/kvm_host.h             | 10 +++-
 arch/arm64/kvm/Makefile                       |  1 +
 arch/arm64/kvm/arm.c                          |  1 +
 arch/arm64/kvm/debug.c                        |  7 +++
 arch/arm64/kvm/etm.c                          | 48 ++++++++++++++++
 arch/arm64/kvm/hyp/nvhe/debug-sr.c            | 56 +++++++++++++++++--
 .../hwtracing/coresight/coresight-etm-perf.c  |  4 ++
 include/kvm/etm.h                             | 43 ++++++++++++++
 8 files changed, 165 insertions(+), 5 deletions(-)
 create mode 100644 arch/arm64/kvm/etm.c
 create mode 100644 include/kvm/etm.h

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2.34.1