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

[Atish Patra <atish.patra@linux.dev>]

On 6/21/26 11:44 PM, Charlie Jenkins wrote:
> On Mon, Jun 08, 2026 at 11:01:31PM -0700, Atish Patra wrote:
>> From: Atish Patra <atishp@rivosinc.com>
>>
>> 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@rivosinc.com>
>> ---
>>   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@rivosinc.com/
>
> Should we follow up with this/maybe this should be accounted for here as
> an alternate id?

Ahh yes. I remember that thread now. Thanks for digging this.
Yes. We should resurrect that patch and use that archid 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
>>
>>