Commit 0a1754ba authored Feb 29, 2024 by Kajol Jain Committed by Sasha Levin Mar 26, 2024

powerpc/hv-gpci: Fix the H_GET_PERF_COUNTER_INFO hcall return value checks



[ 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: 220a0c60 ("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>

parent accdac6b

arch/powerpc/perf/hv-gpci.c

+27 −2

Original line number	Diff line number	Diff line
		@@ -157,6 +157,20 @@ 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;
		@@ -221,6 +235,7 @@ 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)
		@@ -260,13 +275,23 @@ 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;
		}