| Message ID | 20230804101317.460697-1-james.clark@arm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | coresight: Support exclude_guest with Feat_TRF and nVHE | expand |
On Fri, 04 Aug 2023 11:13:10 +0100, James Clark <james.clark@arm.com> 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. > > 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. It'd be nice to have some sort of feature parity, but it seems like a vanishingly small target of users having access to an ETM sink. > > Apart from compilation and checking that the exclude guest settings > are correctly programmed on guest switch, this is untested by me. I'll have a look at the series, but none of my HW fits in this description (my ARMv8.4+ boxes don't have any form of tracing). Thanks, M.
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 >
Hi Marc On 04/08/2023 20:09, Marc Zyngier wrote: > On Fri, 04 Aug 2023 11:13:10 +0100, > James Clark <james.clark@arm.com> 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. >> >> 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. > > It'd be nice to have some sort of feature parity, but it seems like a > vanishingly small target of users having access to an ETM sink. > >> >> Apart from compilation and checking that the exclude guest settings >> are correctly programmed on guest switch, this is untested by me. > > I'll have a look at the series, but none of my HW fits in this > description (my ARMv8.4+ boxes don't have any form of tracing). While I have your attention, we have another series that manages the trace filtering for Guests on VHE, completely within the Coresight etm4x driver here [0]. I personally think, it is good to have the guest filtering for both nVHE and VHE under the KVM control, like we do in this series. I would like your opinion on this. [0] https://lkml.kernel.org/r/20230804085219.260790-1-james.clark@arm.com Suzuki > > Thanks, > > M. >
On Sat, 05 Aug 2023 11:28:39 +0100, Suzuki K Poulose <suzuki.poulose@arm.com> wrote: > > Hi Marc > > On 04/08/2023 20:09, Marc Zyngier wrote: > > On Fri, 04 Aug 2023 11:13:10 +0100, > > James Clark <james.clark@arm.com> 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. > >> > >> 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. > > > > It'd be nice to have some sort of feature parity, but it seems like a > > vanishingly small target of users having access to an ETM sink. > > > >> > >> Apart from compilation and checking that the exclude guest settings > >> are correctly programmed on guest switch, this is untested by me. > > > > I'll have a look at the series, but none of my HW fits in this > > description (my ARMv8.4+ boxes don't have any form of tracing). > > While I have your attention, we have another series that manages the > trace filtering for Guests on VHE, completely within the Coresight etm4x > driver here [0]. I personally think, it is good to have the guest > filtering for both nVHE and VHE under the KVM control, like we do > in this series. I would like your opinion on this. I just quickly reviewed the first two patches of the nVHE series, and I think the shape is a bit wrong. I can absolutely see the interest of preventing extra tracing when a guest is running, but the way this is currently plugged makes it hard to reason about it. > [0] https://lkml.kernel.org/r/20230804085219.260790-1-james.clark@arm.com I'll try to have a look at that one later. Thanks, M.