Unverified Commit 83c5e13b authored by Alexandre Ghiti's avatar Alexandre Ghiti Committed by Palmer Dabbelt
Browse files

riscv: Prepare for user-space perf event mmap support 



Provide all the necessary bits in the generic riscv pmu driver to be
able to mmap perf events in userspace: the heavy lifting lies in the
driver backend, namely the legacy and sbi implementations.

Note that arch_perf_update_userpage is almost a copy of arm64 code.

Signed-off-by: default avatarAlexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: default avatarAndrew Jones <ajones@ventanamicro.com>
Reviewed-by: default avatarAtish Patra <atishp@rivosinc.com>
parent d5ac062d

drivers/perf/riscv_pmu.c

+105 −0
Original line number Diff line number Diff line
@@ -14,9 +14,73 @@ 
#include <linux/perf/riscv_pmu.h>

#include <linux/printk.h>

#include <linux/smp.h>

#include <linux/sched_clock.h>



#include <asm/sbi.h>



static bool riscv_perf_user_access(struct perf_event *event)

{

	return ((event->attr.type == PERF_TYPE_HARDWARE) ||

		(event->attr.type == PERF_TYPE_HW_CACHE) ||

		(event->attr.type == PERF_TYPE_RAW)) &&

		!!(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT);

}



void arch_perf_update_userpage(struct perf_event *event,

			       struct perf_event_mmap_page *userpg, u64 now)

{

	struct clock_read_data *rd;

	unsigned int seq;

	u64 ns;



	userpg->cap_user_time = 0;

	userpg->cap_user_time_zero = 0;

	userpg->cap_user_time_short = 0;

	userpg->cap_user_rdpmc = riscv_perf_user_access(event);



	userpg->pmc_width = 64;



	do {

		rd = sched_clock_read_begin(&seq);



		userpg->time_mult = rd->mult;

		userpg->time_shift = rd->shift;

		userpg->time_zero = rd->epoch_ns;

		userpg->time_cycles = rd->epoch_cyc;

		userpg->time_mask = rd->sched_clock_mask;



		/*

		 * Subtract the cycle base, such that software that

		 * doesn't know about cap_user_time_short still 'works'

		 * assuming no wraps.

		 */

		ns = mul_u64_u32_shr(rd->epoch_cyc, rd->mult, rd->shift);

		userpg->time_zero -= ns;



	} while (sched_clock_read_retry(seq));



	userpg->time_offset = userpg->time_zero - now;



	/*

	 * time_shift is not expected to be greater than 31 due to

	 * the original published conversion algorithm shifting a

	 * 32-bit value (now specifies a 64-bit value) - refer

	 * perf_event_mmap_page documentation in perf_event.h.

	 */

	if (userpg->time_shift == 32) {

		userpg->time_shift = 31;

		userpg->time_mult >>= 1;

	}



	/*

	 * Internal timekeeping for enabled/running/stopped times

	 * is always computed with the sched_clock.

	 */

	userpg->cap_user_time = 1;

	userpg->cap_user_time_zero = 1;

	userpg->cap_user_time_short = 1;

}



static unsigned long csr_read_num(int csr_num)

{

#define switchcase_csr_read(__csr_num, __val)		{\
@@ -171,6 +235,8 @@ int riscv_pmu_event_set_period(struct perf_event *event) 


	local64_set(&hwc->prev_count, (u64)-left);



	perf_event_update_userpage(event);



	return overflow;

}
@@ -267,6 +333,9 @@ static int riscv_pmu_event_init(struct perf_event *event) 
	hwc->idx = -1;

	hwc->event_base = mapped_event;



	if (rvpmu->event_init)

		rvpmu->event_init(event);



	if (!is_sampling_event(event)) {

		/*

		 * For non-sampling runs, limit the sample_period to half
@@ -283,6 +352,39 @@ static int riscv_pmu_event_init(struct perf_event *event) 
	return 0;

}



static int riscv_pmu_event_idx(struct perf_event *event)

{

	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);



	if (!(event->hw.flags & PERF_EVENT_FLAG_USER_READ_CNT))

		return 0;



	if (rvpmu->csr_index)

		return rvpmu->csr_index(event) + 1;



	return 0;

}



static void riscv_pmu_event_mapped(struct perf_event *event, struct mm_struct *mm)

{

	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);



	if (rvpmu->event_mapped) {

		rvpmu->event_mapped(event, mm);

		perf_event_update_userpage(event);

	}

}



static void riscv_pmu_event_unmapped(struct perf_event *event, struct mm_struct *mm)

{

	struct riscv_pmu *rvpmu = to_riscv_pmu(event->pmu);



	if (rvpmu->event_unmapped) {

		rvpmu->event_unmapped(event, mm);

		perf_event_update_userpage(event);

	}

}



struct riscv_pmu *riscv_pmu_alloc(void)

{

	struct riscv_pmu *pmu;
@@ -307,6 +409,9 @@ struct riscv_pmu *riscv_pmu_alloc(void) 
	}

	pmu->pmu = (struct pmu) {

		.event_init	= riscv_pmu_event_init,

		.event_mapped	= riscv_pmu_event_mapped,

		.event_unmapped	= riscv_pmu_event_unmapped,

		.event_idx	= riscv_pmu_event_idx,

		.add		= riscv_pmu_add,

		.del		= riscv_pmu_del,

		.start		= riscv_pmu_start,

include/linux/perf/riscv_pmu.h

+4 −0
Original line number Diff line number Diff line
@@ -55,6 +55,10 @@ struct riscv_pmu { 
	void		(*ctr_start)(struct perf_event *event, u64 init_val);

	void		(*ctr_stop)(struct perf_event *event, unsigned long flag);

	int		(*event_map)(struct perf_event *event, u64 *config);

	void		(*event_init)(struct perf_event *event);

	void		(*event_mapped)(struct perf_event *event, struct mm_struct *mm);

	void		(*event_unmapped)(struct perf_event *event, struct mm_struct *mm);

	uint8_t		(*csr_index)(struct perf_event *event);



	struct cpu_hw_events	__percpu *hw_events;

	struct hlist_node	node;