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Date: Fri, 5 Jan 2024 09:55:38 +0000
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, maz@...nel.org, acme@...nel.org
Cc: 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>, Miguel Luis <miguel.luis@...cle.com>,
Jintack Lim <jintack.lim@...aro.org>, Ard Biesheuvel <ardb@...nel.org>,
Mark Rutland <mark.rutland@....com>, Arnd Bergmann <arnd@...db.de>,
Quentin Perret <qperret@...gle.com>,
Vincent Donnefort <vdonnefort@...gle.com>, Fuad Tabba <tabba@...gle.com>,
Akihiko Odaki <akihiko.odaki@...nix.com>,
Kristina Martsenko <kristina.martsenko@....com>,
Joey Gouly <joey.gouly@....com>, Jing Zhang <jingzhangos@...gle.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 7/7] coresight: Pass guest TRFCR value to KVM
On 04/01/2024 16:27, James Clark wrote:
> Currently the userspace and kernel filters for guests are never set, so
> no trace will be generated for them. Add support for tracing guests by
> passing the desired TRFCR value to KVM so it can be applied to the
> guest.
>
> By writing either E1TRE or E0TRE, filtering on either guest kernel or
> guest userspace is also supported. And if both E1TRE and E0TRE are
> cleared when exclude_guest is set, that option is supported too. 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 (only 5 addresses because the guest runs slowly in the
> model):
>
> $ perf record -e cs_etm//Gu -a -- true
> 5 EL0
>
> 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
>
> Signed-off-by: James Clark <james.clark@....com>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
> ---
> .../coresight/coresight-etm4x-core.c | 42 ++++++++++++++++---
> drivers/hwtracing/coresight/coresight-etm4x.h | 2 +-
> drivers/hwtracing/coresight/coresight-priv.h | 3 ++
> 3 files changed, 40 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> index 34aee59dd147..885d70fd6f40 100644
> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
> @@ -6,6 +6,7 @@
> #include <linux/acpi.h>
> #include <linux/bitops.h>
> #include <linux/kernel.h>
> +#include <linux/kvm_host.h>
> #include <linux/moduleparam.h>
> #include <linux/init.h>
> #include <linux/types.h>
> @@ -271,9 +272,22 @@ static void etm4x_prohibit_trace(struct etmv4_drvdata *drvdata)
> /* If the CPU doesn't support FEAT_TRF, nothing to do */
> if (!drvdata->trfcr)
> return;
> + kvm_etm_set_guest_trfcr(0);
> 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 +300,28 @@ 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);
> +
> + /* Set filters for guests and pass to KVM */
> + 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 so mask it out. */
> + trfcr &= ~TRFCR_EL2_CX;
> + kvm_etm_set_guest_trfcr(trfcr);
> }
>
> #ifdef CONFIG_ETM4X_IMPDEF_FEATURE
> @@ -655,6 +679,12 @@ 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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