linux-kernel - Re: [RFC PATCH 0/3] coresight: Support exclude_guest with Feat

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Message-ID: <63e20343-b95c-308f-ac43-8285ef164caf@arm.com>
Date:   Sat, 5 Aug 2023 11:14:45 +0100
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     James Clark <james.clark@....com>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev
Cc:     Marc Zyngier <maz@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Rob Herring <robh@...nel.org>, linux-kernel@...r.kernel.org,
        Steve Clevenger <scclevenger@...amperecomputing.com>,
        Tanmay Jagdale <tanmay@...vell.com>,
        Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
Subject: Re: [RFC PATCH 0/3] coresight: Support exclude_guest with Feat_TRF
 and nVHE

Cc: Ganpatrao, Steve, Tanmay

On 04/08/2023 11:13, James Clark wrote:
> 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.


If you have a v8.4+ (and not v9) HW, please could you give this a spin ?

Suzuki


> 
> 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
>