Patch "powerpc/hv-gpci: Fix the H_GET_PERF_COUNTER_INFO hcall return value checks" has been added to the 4.19-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 4.19-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     powerpc-hv-gpci-fix-the-h_get_perf_counter_info-hcal.patch
and it can be found in the queue-4.19 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 5bf115678f6c436af8ffa61f59b618a35b0378de
Author: Kajol Jain <kjain@xxxxxxxxxxxxx>
Date:   Thu Feb 29 17:58:47 2024 +0530

    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: 220a0c609ad1 ("powerpc/perf: Add support for the hv gpci (get performance counter info) interface")
    Reported-by: Akanksha J N <akanksha@xxxxxxxxxxxxx>
    Signed-off-by: Kajol Jain <kjain@xxxxxxxxxxxxx>
    Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
    Link: https://msgid.link/20240229122847.101162-1-kjain@xxxxxxxxxxxxx
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/powerpc/perf/hv-gpci.c b/arch/powerpc/perf/hv-gpci.c
index 126409bb5626e..8ae70b5952a54 100644
--- a/arch/powerpc/perf/hv-gpci.c
+++ b/arch/powerpc/perf/hv-gpci.c
@@ -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;
 	}