linux-kernel - [PATCH v4 2/2] cpupower: Fix to return negative value if no permisssion for read

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Message-ID: <2dccdf57-1546-e55e-2efe-3ac91ed7f043@gmail.com>
Date:   Sun, 25 Apr 2021 10:51:00 +0800
From:   徐福海 <xufuhai1992@...il.com>
To:     shuah@...nel.org, Shuah Khan <skhan@...uxfoundation.org>,
        Thomas Renninger <trenn@...e.com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        lishujin@...ishou.com, xufuhai <xufuhai@...ishou.com>
Subject: [PATCH v4 2/2] cpupower: Fix to return negative value if no
 permisssion for read_msr

From: xufuhai <xufuhai@...ishou.com>

If the read_msr function is executed by a non-root user, the function returns 
-1, which means that there is no permission to access /dev/cpu/%d/msr, but 
cpufreq_has_boost_support should also return -1 immediately, and should not
follow the original logic to return 0, which will cause amd The cpupower tool
returns the boost active state as 0.

Reproduce procedure:
        cpupower frequency-info

Reported-by:   yangrui <yangrui@...ishou.com>
Signed-off-by: xufuhai <xufuhai@...ishou.com>
Signed-off-by: chenguanqiao <chenguanqiao@...ishou.com>
Signed-off-by: lishujin <lishujin@...ishou.com>
Reviewed-by: Thomas Renninger <trenn@...e.com>
---
 tools/power/cpupower/utils/helpers/misc.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tools/power/cpupower/utils/helpers/misc.c b/tools/power/cpupower/utils/helpers/misc.c
index fc6e34511721..565f8c414396 100644
--- a/tools/power/cpupower/utils/helpers/misc.c
+++ b/tools/power/cpupower/utils/helpers/misc.c
@@ -16,7 +16,7 @@
 int cpufreq_has_boost_support(unsigned int cpu, int *support, int *active,
                        int *states)
 {
-       int ret;
+       int ret = 0;
        unsigned long long val;

        *support = *active = *states = 0;
@@ -30,18 +30,21 @@ int cpufreq_has_boost_support(unsigned int cpu, int *support, int *active,
                 */

                if (cpupower_cpu_info.caps & CPUPOWER_CAP_AMD_CPB_MSR) {
-                       if (!read_msr(cpu, MSR_AMD_HWCR, &val)) {
+                       /*
+                        * no permission to access /dev/cpu/%d/msr, return -1 immediately,
+                        * and should not follow the original logic to return 0
+                        */
+                       ret = read_msr(cpu, MSR_AMD_HWCR, &val);
+                       if (!ret) {
                                if (!(val & CPUPOWER_AMD_CPBDIS))
                                        *active = 1;
                        }
                } else {
                        ret = amd_pci_get_num_boost_states(active, states);
-                       if (ret)
-                               return ret;
                }
        } else if (cpupower_cpu_info.caps & CPUPOWER_CAP_INTEL_IDA)
                *support = *active = 1;
-       return 0;
+       return ret;
 }

 int cpupower_intel_get_perf_bias(unsigned int cpu)
--
2.24.3 (Apple Git-128)