From: Kajol Jain kjain@linux.ibm.com
[ Upstream commit ad86d7ee43b22aa2ed60fb982ae94b285c1be671 ]
Running event hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/ in one of the system throws below error:
---Logs--- # perf list | grep hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=?/[Kernel PMU event]
# perf stat -v -e hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/ sleep 2 Using CPUID 00800200 Control descriptor is not initialized Warning: hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/ event is not supported by the kernel. failed to read counter hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/
Performance counter stats for 'system wide':
<not supported> hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/
2.000700771 seconds time elapsed
The above error is because of the hcall failure as required permission "Enable Performance Information Collection" is not set. Based on current code, single_gpci_request function did not check the error type incase hcall fails and by default returns EINVAL. But we can have other reasons for hcall failures like H_AUTHORITY/H_PARAMETER with detail_rc as GEN_BUF_TOO_SMALL, for which we need to act accordingly.
Fix this issue by adding new checks in the single_gpci_request and h_gpci_event_init functions.
Result after fix patch changes:
# perf stat -e hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/ sleep 2 Error: No permission to enable hv_gpci/dispatch_timebase_by_processor_processor_time_in_timebase_cycles,phys_processor_idx=0/ event.
Fixes: 220a0c609ad1 ("powerpc/perf: Add support for the hv gpci (get performance counter info) interface") Reported-by: Akanksha J N akanksha@linux.ibm.com Signed-off-by: Kajol Jain kjain@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/20240229122847.101162-1-kjain@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/perf/hv-gpci.c | 29 +++++++++++++++++++++++++++-- 1 file changed, 27 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/perf/hv-gpci.c b/arch/powerpc/perf/hv-gpci.c index ac3f3df57fe39..e85f1962be024 100644 --- a/arch/powerpc/perf/hv-gpci.c +++ b/arch/powerpc/perf/hv-gpci.c @@ -153,6 +153,20 @@ static unsigned long single_gpci_request(u32 req, u32 starting_index,
ret = plpar_hcall_norets(H_GET_PERF_COUNTER_INFO, virt_to_phys(arg), HGPCI_REQ_BUFFER_SIZE); + + /* + * ret value as 'H_PARAMETER' with detail_rc as 'GEN_BUF_TOO_SMALL', + * specifies that the current buffer size cannot accommodate + * all the information and a partial buffer returned. + * Since in this function we are only accessing data for a given starting index, + * we don't need to accommodate whole data and can get required count by + * accessing first entry data. + * Hence hcall fails only incase the ret value is other than H_SUCCESS or + * H_PARAMETER with detail_rc value as GEN_BUF_TOO_SMALL(0x1B). + */ + if (ret == H_PARAMETER && be32_to_cpu(arg->params.detail_rc) == 0x1B) + ret = 0; + if (ret) { pr_devel("hcall failed: 0x%lx\n", ret); goto out; @@ -217,6 +231,7 @@ static int h_gpci_event_init(struct perf_event *event) { u64 count; u8 length; + unsigned long ret;
/* Not our event */ if (event->attr.type != event->pmu->type) @@ -247,13 +262,23 @@ static int h_gpci_event_init(struct perf_event *event) }
/* check if the request works... */ - if (single_gpci_request(event_get_request(event), + ret = single_gpci_request(event_get_request(event), event_get_starting_index(event), event_get_secondary_index(event), event_get_counter_info_version(event), event_get_offset(event), length, - &count)) { + &count); + + /* + * ret value as H_AUTHORITY implies that partition is not permitted to retrieve + * performance information, and required to set + * "Enable Performance Information Collection" option. + */ + if (ret == H_AUTHORITY) + return -EPERM; + + if (ret) { pr_devel("gpci hcall failed\n"); return -EINVAL; }