Re: [PATCH RFC 5/6] riscv: perf: Add driver for Control Transfer Records Ext.

[Charlie Jenkins]

On Wed, May 29, 2024 at 07:53:36PM +0100, Rajnesh Kanwal wrote:
> This adds support for CTR Ext defined in [0]. The extension
> allows to records a maximum for 256 last branch records.
> 
> CTR extension depends on s[m|s]csrind and Sscofpmf extensions.
> 
> Signed-off-by: Rajnesh Kanwal <rkanwal@xxxxxxxxxxxx>
> ---
>  MAINTAINERS                    |   1 +
>  drivers/perf/Kconfig           |  11 +
>  drivers/perf/Makefile          |   1 +
>  drivers/perf/riscv_ctr.c       | 469 +++++++++++++++++++++++++++++++++
>  include/linux/perf/riscv_pmu.h |  33 +++
>  5 files changed, 515 insertions(+)
>  create mode 100644 drivers/perf/riscv_ctr.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index d6b42d5f62da..868e4b0808ab 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -19056,6 +19056,7 @@ M:	Atish Patra <atishp@xxxxxxxxxxxxxx>
>  R:	Anup Patel <anup@xxxxxxxxxxxxxx>
>  L:	linux-riscv@xxxxxxxxxxxxxxxxxxx
>  S:	Supported
> +F:	drivers/perf/riscv_ctr.c
>  F:	drivers/perf/riscv_pmu_common.c
>  F:	drivers/perf/riscv_pmu_dev.c
>  F:	drivers/perf/riscv_pmu_legacy.c
> diff --git a/drivers/perf/Kconfig b/drivers/perf/Kconfig
> index 3c37577b25f7..cca6598be739 100644
> --- a/drivers/perf/Kconfig
> +++ b/drivers/perf/Kconfig
> @@ -110,6 +110,17 @@ config ANDES_CUSTOM_PMU
>  
>  	  If you don't know what to do here, say "Y".
>  
> +config RISCV_CTR
> +       bool "Enable support for Control Transfer Records (CTR)"
> +       depends on PERF_EVENTS && RISCV_PMU
> +       default y
> +       help
> +         Enable support for Control Transfer Records (CTR) which
> +         allows recording branches, Jumps, Calls, returns etc taken in an
> +         execution path. This also supports privilege based filtering. It
> +         captures additional relevant information such as cycle count,
> +         branch misprediction etc.
> +
>  config ARM_PMU_ACPI
>  	depends on ARM_PMU && ACPI
>  	def_bool y
> diff --git a/drivers/perf/Makefile b/drivers/perf/Makefile
> index ba809cc069d5..364b1f66f410 100644
> --- a/drivers/perf/Makefile
> +++ b/drivers/perf/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_RISCV_PMU_COMMON) += riscv_pmu_common.o
>  obj-$(CONFIG_RISCV_PMU_LEGACY) += riscv_pmu_legacy.o
>  obj-$(CONFIG_RISCV_PMU) += riscv_pmu_dev.o
>  obj-$(CONFIG_STARFIVE_STARLINK_PMU) += starfive_starlink_pmu.o
> +obj-$(CONFIG_RISCV_CTR) += riscv_ctr.o
>  obj-$(CONFIG_THUNDERX2_PMU) += thunderx2_pmu.o
>  obj-$(CONFIG_XGENE_PMU) += xgene_pmu.o
>  obj-$(CONFIG_ARM_SPE_PMU) += arm_spe_pmu.o
> diff --git a/drivers/perf/riscv_ctr.c b/drivers/perf/riscv_ctr.c
> new file mode 100644
> index 000000000000..95fda1edda4f
> --- /dev/null
> +++ b/drivers/perf/riscv_ctr.c
> @@ -0,0 +1,469 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Control transfer records extension Helpers.
> + *
> + * Copyright (C) 2024 Rivos Inc.
> + *
> + * Author: Rajnesh Kanwal <rkanwal@xxxxxxxxxxxx>
> + */
> +
> +#define pr_fmt(fmt) "CTR: " fmt
> +
> +#include <linux/bitfield.h>
> +#include <linux/printk.h>
> +#include <linux/types.h>
> +#include <linux/perf_event.h>
> +#include <linux/perf/riscv_pmu.h>
> +#include <linux/cpufeature.h>
> +#include <asm/hwcap.h>
> +#include <asm/csr_ind.h>
> +#include <asm/csr.h>
> +
> +#define CTR_BRANCH_FILTERS_INH  (CTRCTL_EXCINH       | \
> +				 CTRCTL_INTRINH      | \
> +				 CTRCTL_TRETINH      | \
> +				 CTRCTL_TKBRINH      | \
> +				 CTRCTL_INDCALL_INH  | \
> +				 CTRCTL_DIRCALL_INH  | \
> +				 CTRCTL_INDJUMP_INH  | \
> +				 CTRCTL_DIRJUMP_INH  | \
> +				 CTRCTL_CORSWAP_INH  | \
> +				 CTRCTL_RET_INH      | \
> +				 CTRCTL_INDOJUMP_INH | \
> +				 CTRCTL_DIROJUMP_INH)
> +
> +#define CTR_BRANCH_ENABLE_BITS (CTRCTL_KERNEL_ENABLE | CTRCTL_U_ENABLE)
> +
> +/* Branch filters not-supported by CTR extension. */
> +#define CTR_EXCLUDE_BRANCH_FILTERS (PERF_SAMPLE_BRANCH_ABORT_TX	        | \
> +				    PERF_SAMPLE_BRANCH_IN_TX		| \
> +				    PERF_SAMPLE_BRANCH_PRIV_SAVE        | \
> +				    PERF_SAMPLE_BRANCH_NO_TX            | \
> +				    PERF_SAMPLE_BRANCH_COUNTERS)
> +
> +/* Branch filters supported by CTR extension. */
> +#define CTR_ALLOWED_BRANCH_FILTERS (PERF_SAMPLE_BRANCH_USER		| \
> +				    PERF_SAMPLE_BRANCH_KERNEL		| \
> +				    PERF_SAMPLE_BRANCH_HV		| \
> +				    PERF_SAMPLE_BRANCH_ANY		| \
> +				    PERF_SAMPLE_BRANCH_ANY_CALL	        | \
> +				    PERF_SAMPLE_BRANCH_ANY_RETURN	| \
> +				    PERF_SAMPLE_BRANCH_IND_CALL	        | \
> +				    PERF_SAMPLE_BRANCH_COND		| \
> +				    PERF_SAMPLE_BRANCH_IND_JUMP	        | \
> +				    PERF_SAMPLE_BRANCH_HW_INDEX	        | \
> +				    PERF_SAMPLE_BRANCH_NO_FLAGS	        | \
> +				    PERF_SAMPLE_BRANCH_NO_CYCLES	| \
> +				    PERF_SAMPLE_BRANCH_CALL_STACK       | \
> +				    PERF_SAMPLE_BRANCH_CALL		| \
> +				    PERF_SAMPLE_BRANCH_TYPE_SAVE)
> +
> +#define CTR_PERF_BRANCH_FILTERS    (CTR_ALLOWED_BRANCH_FILTERS	        | \
> +				    CTR_EXCLUDE_BRANCH_FILTERS)
> +
> +static u64 allowed_filters __read_mostly;
> +
> +struct ctr_regset {
> +	unsigned long src;
> +	unsigned long target;
> +	unsigned long ctr_data;
> +};
> +
> +static inline u64 get_ctr_src_reg(unsigned int ctr_idx)
> +{
> +	return csr_ind_read(CSR_IREG, CTR_ENTRIES_FIRST, ctr_idx);
> +}
> +
> +static inline u64 get_ctr_tgt_reg(unsigned int ctr_idx)
> +{
> +	return csr_ind_read(CSR_IREG2, CTR_ENTRIES_FIRST, ctr_idx);
> +}
> +
> +static inline u64 get_ctr_data_reg(unsigned int ctr_idx)
> +{
> +	return csr_ind_read(CSR_IREG3, CTR_ENTRIES_FIRST, ctr_idx);
> +}
> +
> +static inline bool ctr_record_valid(u64 ctr_src)
> +{
> +	return !!FIELD_GET(CTRSOURCE_VALID, ctr_src);
> +}
> +
> +static inline int ctr_get_mispredict(u64 ctr_target)
> +{
> +	return FIELD_GET(CTRTARGET_MISP, ctr_target);
> +}
> +
> +static inline unsigned int ctr_get_cycles(u64 ctr_data)
> +{
> +	const unsigned int cce = FIELD_GET(CTRDATA_CCE_MASK, ctr_data);
> +	const unsigned int ccm = FIELD_GET(CTRDATA_CCM_MASK, ctr_data);
> +
> +	if (ctr_data & CTRDATA_CCV)
> +		return 0;
> +
> +	/* Formula to calculate cycles from spec: (2^12 + CCM) << CCE-1 */
> +	if (cce > 0)
> +		return (4096 + ccm) << (cce - 1);
> +
> +	return FIELD_GET(CTRDATA_CCM_MASK, ctr_data);
> +}
> +
> +static inline unsigned int ctr_get_type(u64 ctr_data)
> +{
> +	return FIELD_GET(CTRDATA_TYPE_MASK, ctr_data);
> +}
> +
> +static inline unsigned int ctr_get_depth(u64 ctr_depth)
> +{
> +	/* Depth table from CTR Spec: 2.4 sctrdepth.
> +	 *
> +	 * sctrdepth.depth       Depth
> +	 * 000			- 16
> +	 * 001			- 32
> +	 * 010			- 64
> +	 * 011			- 128
> +	 * 100			- 256
> +	 *
> +	 * Depth = 16 * 2 ^ (ctrdepth.depth)
> +	 * or
> +	 * Depth = 16 << ctrdepth.depth.
> +	 */
> +	return 16 << FIELD_GET(SCTRDEPTH_MASK, ctr_depth);
> +}
> +
> +/* Reads CTR entry at idx and stores it in entry struct. */
> +static bool capture_ctr_regset(struct ctr_regset *entry, unsigned int idx)
> +{
> +	entry->src = get_ctr_src_reg(idx);
> +
> +	if (!ctr_record_valid(entry->src))
> +		return false;
> +
> +	entry->src = entry->src & (~CTRSOURCE_VALID);
> +	entry->target = get_ctr_tgt_reg(idx);
> +	entry->ctr_data = get_ctr_data_reg(idx);
> +
> +	return true;
> +}
> +
> +static u64 branch_type_to_ctr(int branch_type)
> +{
> +	u64 config = CTR_BRANCH_FILTERS_INH | CTRCTL_LCOFIFRZ;
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_USER)
> +		config |= CTRCTL_U_ENABLE;
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_KERNEL)
> +		config |= CTRCTL_KERNEL_ENABLE;
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_HV) {
> +		if (riscv_isa_extension_available(NULL, h))
> +			config |= CTRCTL_KERNEL_ENABLE;
> +	}
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_ANY) {
> +		config &= ~CTR_BRANCH_FILTERS_INH;
> +		return config;
> +	}
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_ANY_CALL) {
> +		config &= ~CTRCTL_INDCALL_INH;
> +		config &= ~CTRCTL_DIRCALL_INH;
> +		config &= ~CTRCTL_EXCINH;
> +		config &= ~CTRCTL_INTRINH;
> +	}
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_ANY_RETURN)
> +		config &= ~(CTRCTL_RET_INH | CTRCTL_TRETINH);
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_IND_CALL)
> +		config &= ~CTRCTL_INDCALL_INH;
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_COND)
> +		config &= ~CTRCTL_TKBRINH;
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_CALL_STACK) {
> +		config &= ~(CTRCTL_INDCALL_INH | CTRCTL_DIRCALL_INH |
> +			    CTRCTL_RET_INH);
> +		config |= CTRCTL_RASEMU;
> +	}
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_IND_JUMP) {
> +		config &= ~CTRCTL_INDJUMP_INH;
> +		config &= ~CTRCTL_INDOJUMP_INH;
> +	}
> +
> +	if (branch_type & PERF_SAMPLE_BRANCH_CALL)
> +		config &= ~CTRCTL_DIRCALL_INH;
> +
> +	return config;
> +}
> +
> +static const int ctr_perf_map[] = {
> +	[CTRDATA_TYPE_NONE]			= PERF_BR_UNKNOWN,
> +	[CTRDATA_TYPE_EXCEPTION]		= PERF_BR_SYSCALL,
> +	[CTRDATA_TYPE_INTERRUPT]		= PERF_BR_IRQ,
> +	[CTRDATA_TYPE_TRAP_RET]			= PERF_BR_ERET,
> +	[CTRDATA_TYPE_NONTAKEN_BRANCH]		= PERF_BR_COND,
> +	[CTRDATA_TYPE_TAKEN_BRANCH]		= PERF_BR_COND,
> +	[CTRDATA_TYPE_RESERVED_6]		= PERF_BR_UNKNOWN,
> +	[CTRDATA_TYPE_RESERVED_7]		= PERF_BR_UNKNOWN,
> +	[CTRDATA_TYPE_INDIRECT_CALL]		= PERF_BR_IND_CALL,
> +	[CTRDATA_TYPE_DIRECT_CALL]		= PERF_BR_CALL,
> +	[CTRDATA_TYPE_INDIRECT_JUMP]		= PERF_BR_UNCOND,
> +	[CTRDATA_TYPE_DIRECT_JUMP]		= PERF_BR_UNKNOWN,
> +	[CTRDATA_TYPE_CO_ROUTINE_SWAP]		= PERF_BR_UNKNOWN,
> +	[CTRDATA_TYPE_RETURN]			= PERF_BR_RET,
> +	[CTRDATA_TYPE_OTHER_INDIRECT_JUMP]	= PERF_BR_IND,
> +	[CTRDATA_TYPE_OTHER_DIRECT_JUMP]	= PERF_BR_UNKNOWN,
> +};
> +
> +static void ctr_set_perf_entry_type(struct perf_branch_entry *entry,
> +				    u64 ctr_data)
> +{
> +	int ctr_type = ctr_get_type(ctr_data);
> +
> +	entry->type = ctr_perf_map[ctr_type];
> +	if (entry->type == PERF_BR_UNKNOWN)
> +		pr_warn("%d - unknown branch type captured\n", ctr_type);
> +}
> +
> +static void capture_ctr_flags(struct perf_branch_entry *entry,
> +			      struct perf_event *event, u64 ctr_data,
> +			      u64 ctr_target)
> +{
> +	if (branch_sample_type(event))
> +		ctr_set_perf_entry_type(entry, ctr_data);
> +
> +	if (!branch_sample_no_cycles(event))
> +		entry->cycles = ctr_get_cycles(ctr_data);
> +
> +	if (!branch_sample_no_flags(event)) {
> +		entry->abort = 0;
> +		entry->mispred = ctr_get_mispredict(ctr_target);
> +		entry->predicted = !entry->mispred;
> +	}
> +
> +	if (branch_sample_priv(event))
> +		entry->priv = PERF_BR_PRIV_UNKNOWN;
> +}
> +
> +
> +static void ctr_regset_to_branch_entry(struct cpu_hw_events *cpuc,
> +				       struct perf_event *event,
> +				       struct ctr_regset *regset,
> +				       unsigned int idx)
> +{
> +	struct perf_branch_entry *entry = &cpuc->branches->branch_entries[idx];
> +
> +	perf_clear_branch_entry_bitfields(entry);
> +	entry->from = regset->src;
> +	entry->to = regset->target & (~CTRTARGET_MISP);
> +	capture_ctr_flags(entry, event, regset->ctr_data, regset->target);
> +}
> +
> +static void ctr_read_entries(struct cpu_hw_events *cpuc,
> +			     struct perf_event *event,
> +			     unsigned int depth)
> +{
> +	struct ctr_regset entry = {};
> +	u64 ctr_ctl;
> +	int i;
> +
> +	ctr_ctl = csr_read_clear(CSR_CTRCTL, CTR_BRANCH_ENABLE_BITS);
> +
> +	for (i = 0; i < depth; i++) {
> +		if (!capture_ctr_regset(&entry, i))
> +			break;
> +
> +		ctr_regset_to_branch_entry(cpuc, event, &entry, i);
> +	}
> +
> +	csr_set(CSR_CTRCTL, ctr_ctl & CTR_BRANCH_ENABLE_BITS);
> +
> +	cpuc->branches->branch_stack.nr = i;
> +	cpuc->branches->branch_stack.hw_idx = 0;
> +}
> +
> +bool riscv_pmu_ctr_valid(struct perf_event *event)
> +{
> +	u64 branch_type = event->attr.branch_sample_type;
> +
> +	if (branch_type & ~allowed_filters) {
> +		pr_debug_once("Requested branch filters not supported 0x%llx\n",
> +				branch_type & ~allowed_filters);
> +		return false;
> +	}
> +
> +	return true;
> +}
> +
> +void riscv_pmu_ctr_consume(struct cpu_hw_events *cpuc, struct perf_event *event)
> +{
> +	unsigned int depth = to_riscv_pmu(event->pmu)->ctr_depth;
> +
> +	ctr_read_entries(cpuc, event, depth);
> +
> +	/* Clear frozen bit. */
> +	csr_clear(CSR_SCTRSTATUS, SCTRSTATUS_FROZEN);
> +}
> +
> +static void riscv_pmu_ctr_clear(void)
> +{
> +	/* FIXME: Replace with sctrclr instruction once support is merged
> +	 * into toolchain.
> +	 */
> +	asm volatile(".4byte 0x10400073\n" ::: "memory");
> +	csr_write(CSR_SCTRSTATUS, 0);
> +}
> +
> +/*
> + * On context switch in, we need to make sure no samples from previous user
> + * are left in the CTR.
> + *
> + * On ctxswin, sched_in = true, called after the PMU has started
> + * On ctxswout, sched_in = false, called before the PMU is stopped
> + */
> +void riscv_pmu_ctr_sched_task(struct perf_event_pmu_context *pmu_ctx,
> +			      bool sched_in)
> +{
> +	struct riscv_pmu *rvpmu = to_riscv_pmu(pmu_ctx->pmu);
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
> +
> +	if (cpuc->ctr_users && sched_in)
> +		riscv_pmu_ctr_clear();
> +}
> +
> +void riscv_pmu_ctr_enable(struct perf_event *event)
> +{
> +	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
> +	u64 branch_type = event->attr.branch_sample_type;
> +	u64 ctr;
> +
> +	if (!cpuc->ctr_users++ && !event->total_time_running)
> +		riscv_pmu_ctr_clear();
> +
> +	ctr = branch_type_to_ctr(branch_type);
> +	csr_write(CSR_CTRCTL, ctr);
> +
> +	perf_sched_cb_inc(event->pmu);
> +}
> +
> +void riscv_pmu_ctr_disable(struct perf_event *event)
> +{
> +	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);
> +	struct cpu_hw_events *cpuc = this_cpu_ptr(rvpmu->hw_events);
> +
> +	/* Clear CTRCTL to disable the recording. */
> +	csr_write(CSR_CTRCTL, 0);
> +
> +	cpuc->ctr_users--;
> +	WARN_ON_ONCE(cpuc->ctr_users < 0);
> +
> +	perf_sched_cb_dec(event->pmu);
> +}
> +
> +/*
> + * Check for hardware supported perf filters here. To avoid missing
> + * any new added filter in perf, we do a BUILD_BUG_ON check, so make sure
> + * to update CTR_ALLOWED_BRANCH_FILTERS or CTR_EXCLUDE_BRANCH_FILTERS
> + * defines when adding support for it in below function.
> + */
> +static void __init check_available_filters(void)
> +{
> +	u64 ctr_ctl;
> +
> +	/*
> +	 * Ensure both perf branch filter allowed and exclude
> +	 * masks are always in sync with the generic perf ABI.
> +	 */
> +	BUILD_BUG_ON(CTR_PERF_BRANCH_FILTERS != (PERF_SAMPLE_BRANCH_MAX - 1));
> +
> +	allowed_filters = PERF_SAMPLE_BRANCH_USER      |
> +			  PERF_SAMPLE_BRANCH_KERNEL    |
> +			  PERF_SAMPLE_BRANCH_ANY       |
> +			  PERF_SAMPLE_BRANCH_HW_INDEX  |
> +			  PERF_SAMPLE_BRANCH_NO_FLAGS  |
> +			  PERF_SAMPLE_BRANCH_NO_CYCLES |
> +			  PERF_SAMPLE_BRANCH_TYPE_SAVE;
> +
> +	csr_write(CSR_CTRCTL, ~0);
> +	ctr_ctl = csr_read(CSR_CTRCTL);
> +
> +	if (riscv_isa_extension_available(NULL, h))
> +		allowed_filters |= PERF_SAMPLE_BRANCH_HV;
> +
> +	if (ctr_ctl & (CTRCTL_INDCALL_INH | CTRCTL_DIRCALL_INH))
> +		allowed_filters |= PERF_SAMPLE_BRANCH_ANY_CALL;
> +
> +	if (ctr_ctl & (CTRCTL_RET_INH | CTRCTL_TRETINH))
> +		allowed_filters |= PERF_SAMPLE_BRANCH_ANY_RETURN;
> +
> +	if (ctr_ctl & CTRCTL_INDCALL_INH)
> +		allowed_filters |= PERF_SAMPLE_BRANCH_IND_CALL;
> +
> +	if (ctr_ctl & CTRCTL_TKBRINH)
> +		allowed_filters |= PERF_SAMPLE_BRANCH_COND;
> +
> +	if (ctr_ctl & CTRCTL_RASEMU)
> +		allowed_filters |= PERF_SAMPLE_BRANCH_CALL_STACK;
> +
> +	if (ctr_ctl & (CTRCTL_INDOJUMP_INH | CTRCTL_INDJUMP_INH))
> +		allowed_filters |= PERF_SAMPLE_BRANCH_IND_JUMP;
> +
> +	if (ctr_ctl & CTRCTL_DIRCALL_INH)
> +		allowed_filters |= PERF_SAMPLE_BRANCH_CALL;
> +}
> +
> +void riscv_pmu_ctr_starting_cpu(void)
> +{
> +	if (!riscv_isa_extension_available(NULL, SxCTR) ||
> +	    !riscv_isa_extension_available(NULL, SSCOFPMF) ||
> +	    !riscv_isa_extension_available(NULL, SxCSRIND))
> +		return;
> +
> +	/* Set depth to maximum. */
> +	csr_write(CSR_SCTRDEPTH, SCTRDEPTH_MASK);
> +}
> +
> +void riscv_pmu_ctr_dying_cpu(void)
> +{
> +	if (!riscv_isa_extension_available(NULL, SxCTR) ||
> +	    !riscv_isa_extension_available(NULL, SSCOFPMF) ||
> +	    !riscv_isa_extension_available(NULL, SxCSRIND))
> +		return;
> +
> +	/* Clear and reset CTR CSRs. */
> +	csr_write(CSR_SCTRDEPTH, 0);
> +	csr_write(CSR_CTRCTL, 0);
> +	riscv_pmu_ctr_clear();
> +}
> +
> +void __init riscv_pmu_ctr_init(struct riscv_pmu *riscv_pmu)
> +{
> +	if (!riscv_isa_extension_available(NULL, SxCTR) ||
> +	    !riscv_isa_extension_available(NULL, SSCOFPMF) ||
> +	    !riscv_isa_extension_available(NULL, SxCSRIND))
> +		return;
> +
> +	check_available_filters();
> +
> +	/* Set depth to maximum. */
> +	csr_write(CSR_SCTRDEPTH, SCTRDEPTH_MASK);
> +	riscv_pmu->ctr_depth = ctr_get_depth(csr_read(CSR_SCTRDEPTH));
> +
> +	pr_info("Perf CTR available, with %d depth\n", riscv_pmu->ctr_depth);
> +}
> +
> +void __init riscv_pmu_ctr_finish(struct riscv_pmu *riscv_pmu)

I don't think it is valid for this function and riscv_pmu_ctr_init() to
be marked as __init since they are called from rvpmu_device_probe()
which is not marked as __init. modpost highlights this issue with the
warnings:

WARNING: modpost: vmlinux: section mismatch in reference: rvpmu_device_probe+0x18c (section: .text) -> riscv_pmu_ctr_init (section: .init.text)
WARNING: modpost: vmlinux: section mismatch in reference: rvpmu_device_probe+0x288 (section: .text) -> riscv_pmu_ctr_finish (section: .init.text)

- Charlie

> +{
> +	if (!riscv_pmu_ctr_supported(riscv_pmu))
> +		return;
> +
> +	csr_write(CSR_SCTRDEPTH, 0);
> +	csr_write(CSR_CTRCTL, 0);
> +	riscv_pmu_ctr_clear();
> +	riscv_pmu->ctr_depth = 0;
> +}
> diff --git a/include/linux/perf/riscv_pmu.h b/include/linux/perf/riscv_pmu.h
> index 5a6b840018bd..455d2386936f 100644
> --- a/include/linux/perf/riscv_pmu.h
> +++ b/include/linux/perf/riscv_pmu.h
> @@ -104,6 +104,39 @@ struct riscv_pmu *riscv_pmu_alloc(void);
>  int riscv_pmu_get_hpm_info(u32 *hw_ctr_width, u32 *num_hw_ctr);
>  #endif
>  
> +static inline bool riscv_pmu_ctr_supported(struct riscv_pmu *pmu)
> +{
> +	return !!pmu->ctr_depth;
> +}
> +
>  #endif /* CONFIG_RISCV_PMU_COMMON */
>  
> +#ifdef CONFIG_RISCV_CTR
> +
> +bool riscv_pmu_ctr_valid(struct perf_event *event);
> +void riscv_pmu_ctr_consume(struct cpu_hw_events *cpuc, struct perf_event *event);
> +void riscv_pmu_ctr_sched_task(struct perf_event_pmu_context *pmu_ctx, bool sched_in);
> +void riscv_pmu_ctr_enable(struct perf_event *event);
> +void riscv_pmu_ctr_disable(struct perf_event *event);
> +void riscv_pmu_ctr_dying_cpu(void);
> +void riscv_pmu_ctr_starting_cpu(void);
> +void riscv_pmu_ctr_init(struct riscv_pmu *riscv_pmu);
> +void riscv_pmu_ctr_finish(struct riscv_pmu *riscv_pmu);
> +
> +#else
> +
> +static inline bool riscv_pmu_ctr_valid(struct perf_event *event) { return false; }
> +static inline void riscv_pmu_ctr_consume(struct cpu_hw_events *cpuc,
> +				      struct perf_event *event) { }
> +static inline void riscv_pmu_ctr_sched_task(struct perf_event_pmu_context *,
> +					    bool sched_in) { }
> +static inline void riscv_pmu_ctr_enable(struct perf_event *event) { }
> +static inline void riscv_pmu_ctr_disable(struct perf_event *event) { }
> +static inline void riscv_pmu_ctr_dying_cpu(void) { }
> +static inline void riscv_pmu_ctr_starting_cpu(void) { }
> +static inline void riscv_pmu_ctr_init(struct riscv_pmu *riscv_pmu) { }
> +static inline void riscv_pmu_ctr_finish(struct riscv_pmu *riscv_pmu) { }
> +
> +#endif /* CONFIG_RISCV_CTR */
> +
>  #endif /* _RISCV_PMU_H */
> -- 
> 2.34.1
> 
> 
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