Re: [PATCH v6 17/21] RISC-V: perf: Add Qemu virt machine events

[Charlie Jenkins]

On Mon, Jun 08, 2026 at 11:01:31PM -0700, Atish Patra wrote:
> From: Atish Patra <atishp@xxxxxxxxxxxx>
> 
> Qemu virt machine supports a very minimal set of legacy perf events.
> Add them to the vendor table so that users can use them when
> counter delegation is enabled.
> 
> Signed-off-by: Atish Patra <atishp@xxxxxxxxxxxx>
> ---
>  arch/riscv/include/asm/vendorid_list.h |  4 ++++
>  drivers/perf/riscv_pmu_sbi.c           | 36 ++++++++++++++++++++++++++++++++++
>  2 files changed, 40 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/vendorid_list.h b/arch/riscv/include/asm/vendorid_list.h
> index 7f5030ee1fcf..603aa2b21c0b 100644
> --- a/arch/riscv/include/asm/vendorid_list.h
> +++ b/arch/riscv/include/asm/vendorid_list.h
> @@ -11,4 +11,8 @@
>  #define SIFIVE_VENDOR_ID	0x489
>  #define THEAD_VENDOR_ID		0x5b7
>  
> +#define QEMU_VIRT_VENDOR_ID		0x000
> +#define QEMU_VIRT_IMPL_ID		0x000
> +#define QEMU_VIRT_ARCH_ID		0x000

Palmer proposed a change to this a while ago to set the archid for qemu
as 42 but it looks like it was never merged in qemu, but it was merged
into the riscv spec.

Here is the spec PR: https://github.com/riscv/riscv-isa-manual/pull/1213
Here is the current spec: https://github.com/riscv/riscv-isa-manual/blob/main/marchid.md
Here is the QEMU patch: https://lore.kernel.org/all/20240131182430.20174-1-palmer@xxxxxxxxxxxx/

Should we follow up with this/maybe this should be accounted for here as
an alternate id?

- Charlie

> +
>  #endif
> diff --git a/drivers/perf/riscv_pmu_sbi.c b/drivers/perf/riscv_pmu_sbi.c
> index 00b84b28117a..74acac54328e 100644
> --- a/drivers/perf/riscv_pmu_sbi.c
> +++ b/drivers/perf/riscv_pmu_sbi.c
> @@ -26,6 +26,7 @@
>  #include <asm/sbi.h>
>  #include <asm/cpufeature.h>
>  #include <asm/vendor_extensions.h>
> +#include <asm/vendorid_list.h>
>  #include <asm/vendor_extensions/andes.h>
>  #include <asm/hwcap.h>
>  #include <asm/csr_ind.h>
> @@ -453,7 +454,42 @@ struct riscv_vendor_pmu_events {
>  	  .hw_event_map = _hw_event_map, .cache_event_map = _cache_event_map, \
>  	  .attrs_events = _attrs },
>  
> +/* QEMU virt PMU events */
> +static const struct riscv_pmu_event qemu_virt_hw_event_map[PERF_COUNT_HW_MAX] = {
> +	PERF_MAP_ALL_UNSUPPORTED,
> +	[PERF_COUNT_HW_CPU_CYCLES]		= {0x01, 0xFFFFFFF8},
> +	[PERF_COUNT_HW_INSTRUCTIONS]		= {0x02, 0xFFFFFFF8}
> +};
> +
> +static const struct riscv_pmu_event qemu_virt_cache_event_map[PERF_COUNT_HW_CACHE_MAX]
> +						[PERF_COUNT_HW_CACHE_OP_MAX]
> +						[PERF_COUNT_HW_CACHE_RESULT_MAX] = {
> +	PERF_CACHE_MAP_ALL_UNSUPPORTED,
> +	[C(DTLB)][C(OP_READ)][C(RESULT_MISS)]	= {0x10019, 0xFFFFFFF8},
> +	[C(DTLB)][C(OP_WRITE)][C(RESULT_MISS)]	= {0x1001B, 0xFFFFFFF8},
> +
> +	[C(ITLB)][C(OP_READ)][C(RESULT_MISS)]	= {0x10021, 0xFFFFFFF8},
> +};
> +
> +RVPMU_EVENT_CMASK_ATTR(cycles, cycles, 0x01, 0xFFFFFFF8);
> +RVPMU_EVENT_CMASK_ATTR(instructions, instructions, 0x02, 0xFFFFFFF8);
> +RVPMU_EVENT_CMASK_ATTR(dTLB-load-misses, dTLB_load_miss, 0x10019, 0xFFFFFFF8);
> +RVPMU_EVENT_CMASK_ATTR(dTLB-store-misses, dTLB_store_miss, 0x1001B, 0xFFFFFFF8);
> +RVPMU_EVENT_CMASK_ATTR(iTLB-load-misses, iTLB_load_miss, 0x10021, 0xFFFFFFF8);
> +
> +static struct attribute *qemu_virt_event_group[] = {
> +	RVPMU_EVENT_ATTR_PTR(cycles),
> +	RVPMU_EVENT_ATTR_PTR(instructions),
> +	RVPMU_EVENT_ATTR_PTR(dTLB_load_miss),
> +	RVPMU_EVENT_ATTR_PTR(dTLB_store_miss),
> +	RVPMU_EVENT_ATTR_PTR(iTLB_load_miss),
> +	NULL,
> +};
> +
>  static struct riscv_vendor_pmu_events pmu_vendor_events_table[] = {
> +	RISCV_VENDOR_PMU_EVENTS(QEMU_VIRT_VENDOR_ID, QEMU_VIRT_ARCH_ID, QEMU_VIRT_IMPL_ID,
> +				qemu_virt_hw_event_map, qemu_virt_cache_event_map,
> +				qemu_virt_event_group)
>  };
>  
>  static const struct riscv_pmu_event *current_pmu_hw_event_map;
> 
> -- 
> 2.53.0-Meta
> 
>