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Date: Tue, 12 Sep 2023 18:37:42 +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,
broonie@...nel.org, Marc Zyngier <maz@...nel.org>
Cc: maz@...nel.org, 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>,
James Morse <james.morse@....com>,
Kristina Martsenko <kristina.martsenko@....com>,
Anshuman Khandual <anshuman.khandual@....com>,
Rob Herring <robh@...nel.org>,
Jintack Lim <jintack.lim@...aro.org>,
Joey Gouly <joey.gouly@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] coresight: Allow guests to be traced when FEAT_TRF
and VHE are present
Hi James
On 04/09/2023 15:07, James Clark wrote:
> Currently the userspace and kernel filters for guests are never set, so
> no trace will be generated for them. Add it by writing to the guest
> filters when exclude_guest isn't set. By writing either E1TRE or E0TRE,
> filtering on either guest kernel or guest userspace is also supported.
>
> Since TRFCR_EL1 access is trapped, this can't be modified by the guest.
>
> This change also brings exclude_host support which is difficult to add
> as a separate commit without excess churn and resulting in no trace at
> all.
>
> Testing
> =======
>
> The addresses were counted with the following:
>
> $ perf report -D | grep -Eo 'EL2|EL1|EL0' | sort | uniq -c
>
> Guest kernel only:
>
> $ perf record -e cs_etm//Gk -a -- true
> 535 EL1
> 1 EL2
>
> Guest user only (0 addresses expected because the guest OS hasn't reached
> userspace yet):
>
> $ perf record -e cs_etm//Gu -a -- true
>
> Host kernel only:
>
> $ perf record -e cs_etm//Hk -a -- true
> 3501 EL2
>
> Host userspace only:
>
> $ perf record -e cs_etm//Hu -a -- true
> 408 EL0
> 1 EL2
>
> Reviewed-by: Mark Brown <broonie@...nel.org> (sysreg)
> Signed-off-by: James Clark <james.clark@....com>
> ---
> arch/arm64/tools/sysreg | 4 ++
> .../coresight/coresight-etm4x-core.c | 51 ++++++++++++++++---
> drivers/hwtracing/coresight/coresight-etm4x.h | 2 +-
> drivers/hwtracing/coresight/coresight-priv.h | 3 ++
> 4 files changed, 53 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
> index 6ca7db69d6c9..cae9139b6c05 100644
> --- a/arch/arm64/tools/sysreg
> +++ b/arch/arm64/tools/sysreg
> @@ -2531,3 +2531,7 @@ EndSysreg
> Sysreg TRFCR_EL2 3 4 1 2 1
> Fields TRFCR_EL2
> EndSysreg
> +
> +Sysreg TRFCR_EL12 3 5 1 2 1
> +Fields TRFCR_ELx
> +EndSysreg
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 77b0271ce6eb..6c16a14d6fbe 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -274,6 +274,18 @@ static void etm4x_prohibit_trace(struct etmv4_drvdata *drvdata)
> cpu_prohibit_trace();
> }
>
> +static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata)
> +{
> + u64 trfcr = drvdata->trfcr;
> +
> + if (drvdata->config.mode & ETM_MODE_EXCL_KERN)
> + trfcr &= ~TRFCR_ELx_ExTRE;
> + if (drvdata->config.mode & ETM_MODE_EXCL_USER)
> + trfcr &= ~TRFCR_ELx_E0TRE;
> +
> + return trfcr;
> +}
> +
> /*
> * etm4x_allow_trace - Allow CPU tracing in the respective ELs,
> * as configured by the drvdata->config.mode for the current
> @@ -286,18 +298,39 @@ static void etm4x_prohibit_trace(struct etmv4_drvdata *drvdata)
> */
> static void etm4x_allow_trace(struct etmv4_drvdata *drvdata)
> {
> - u64 trfcr = drvdata->trfcr;
> + u64 trfcr;
>
> /* If the CPU doesn't support FEAT_TRF, nothing to do */
> - if (!trfcr)
> + if (!drvdata->trfcr)
> return;
>
> - if (drvdata->config.mode & ETM_MODE_EXCL_KERN)
> - trfcr &= ~TRFCR_ELx_ExTRE;
> - if (drvdata->config.mode & ETM_MODE_EXCL_USER)
> - trfcr &= ~TRFCR_ELx_E0TRE;
> + if (drvdata->config.mode & ETM_MODE_EXCL_HOST)
> + trfcr = drvdata->trfcr & ~(TRFCR_ELx_ExTRE | TRFCR_ELx_E0TRE);
> + else
> + trfcr = etm4x_get_kern_user_filter(drvdata);
>
> write_trfcr(trfcr);
> +
> + /*
> + * Filters for EL1 and EL0 (when running a guest) are stored in
> + * TRFCR_EL1 so write it there for VHE. For nVHE, the filters in
> + * have to be re-applied when switching to the guest instead.
> + */
> + if (!is_kernel_in_hyp_mode())
> + return;
> +
> + if (drvdata->config.mode & ETM_MODE_EXCL_GUEST)
> + trfcr = drvdata->trfcr & ~(TRFCR_ELx_ExTRE | TRFCR_ELx_E0TRE);
> + else
> + trfcr = etm4x_get_kern_user_filter(drvdata);
> +
> + /*
> + * TRFCR_EL1 doesn't have CX and TRFCR_EL1.TS has no effect when TS is
> + * set in EL2 so mask them out.
> + */
> + trfcr &= ~(TRFCR_ELx_TS_MASK | TRFCR_EL2_CX);
> +
> + write_sysreg_s(trfcr, SYS_TRFCR_EL12);
While I agree with the intention of the patch, I am not sure if we
should do the TRFCR_EL1 (via TRFCR_EL12) updates from CoreSight driver.
It might be much better to do it from the KVM for both VHE and nVHE.
Marc
What are your thoughts on this ?
Suzuki
> }
>
> #ifdef CONFIG_ETM4X_IMPDEF_FEATURE
> @@ -655,6 +688,12 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
> if (attr->exclude_user)
> config->mode = ETM_MODE_EXCL_USER;
>
> + if (attr->exclude_host)
> + config->mode |= ETM_MODE_EXCL_HOST;
> +
> + if (attr->exclude_guest)
> + config->mode |= ETM_MODE_EXCL_GUEST;
> +
> /* Always start from the default config */
> etm4_set_default_config(config);
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
> index 20e2e4cb7614..3f170599822f 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x.h
> +++ b/drivers/hwtracing/coresight/coresight-etm4x.h
> @@ -841,7 +841,7 @@ enum etm_impdef_type {
> * @s_ex_level: Secure ELs where tracing is supported.
> */
> struct etmv4_config {
> - u32 mode;
> + u64 mode;
> u32 pe_sel;
> u32 cfg;
> u32 eventctrl0;
> diff --git a/drivers/hwtracing/coresight/coresight-priv.h b/drivers/hwtracing/coresight/coresight-priv.h
> index 767076e07970..727dd27ba800 100644
> --- a/drivers/hwtracing/coresight/coresight-priv.h
> +++ b/drivers/hwtracing/coresight/coresight-priv.h
> @@ -39,6 +39,9 @@
>
> #define ETM_MODE_EXCL_KERN BIT(30)
> #define ETM_MODE_EXCL_USER BIT(31)
> +#define ETM_MODE_EXCL_HOST BIT(32)
> +#define ETM_MODE_EXCL_GUEST BIT(33)
> +
> struct cs_pair_attribute {
> struct device_attribute attr;
> u32 lo_off;
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