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authorSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>2016-10-08 12:42:38 -0700
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-10-09 18:54:13 +0200
commitf9f4872df6e1801572949f8a370c886122d4b6da (patch)
treedc0a321711d1792ea197e67b478683f78b53fac8 /drivers/cpufreq
parentb6e251178286eff8bbd2c01a1b6aa7a317eb3c67 (diff)
cpufreq: intel_pstate: Fix unsafe HWP MSR access
This is a requirement that MSR MSR_PM_ENABLE must be set to 0x01 before reading MSR_HWP_CAPABILITIES on a given CPU. If cpufreq init() is scheduled on a CPU which is not same as policy->cpu or migrates to a different CPU before calling msr read for MSR_HWP_CAPABILITIES, it is possible that MSR_PM_ENABLE was not to set to 0x01 on that CPU. This will cause GP fault. So like other places in this path rdmsrl_on_cpu should be used instead of rdmsrl. Moreover the scope of MSR_HWP_CAPABILITIES is on per thread basis, so it should be read from the same CPU, for which MSR MSR_HWP_REQUEST is getting set. dmesg dump or warning: [ 22.014488] WARNING: CPU: 139 PID: 1 at arch/x86/mm/extable.c:50 ex_handler_rdmsr_unsafe+0x68/0x70 [ 22.014492] unchecked MSR access error: RDMSR from 0x771 [ 22.014493] Modules linked in: [ 22.014507] CPU: 139 PID: 1 Comm: swapper/0 Not tainted 4.7.5+ #1 ... ... [ 22.014516] Call Trace: [ 22.014542] [<ffffffff813d7dd1>] dump_stack+0x63/0x82 [ 22.014558] [<ffffffff8107bc8b>] __warn+0xcb/0xf0 [ 22.014561] [<ffffffff8107bcff>] warn_slowpath_fmt+0x4f/0x60 [ 22.014563] [<ffffffff810676f8>] ex_handler_rdmsr_unsafe+0x68/0x70 [ 22.014564] [<ffffffff810677d9>] fixup_exception+0x39/0x50 [ 22.014604] [<ffffffff8102e400>] do_general_protection+0x80/0x150 [ 22.014610] [<ffffffff817f9ec8>] general_protection+0x28/0x30 [ 22.014635] [<ffffffff81687940>] ? get_target_pstate_use_performance+0xb0/0xb0 [ 22.014642] [<ffffffff810600c7>] ? native_read_msr+0x7/0x40 [ 22.014657] [<ffffffff81688123>] intel_pstate_hwp_set+0x23/0x130 [ 22.014660] [<ffffffff81688406>] intel_pstate_set_policy+0x1b6/0x340 [ 22.014662] [<ffffffff816829bb>] cpufreq_set_policy+0xeb/0x2c0 [ 22.014664] [<ffffffff81682f39>] cpufreq_init_policy+0x79/0xe0 [ 22.014666] [<ffffffff81682cb0>] ? cpufreq_update_policy+0x120/0x120 [ 22.014669] [<ffffffff816833a6>] cpufreq_online+0x406/0x820 [ 22.014671] [<ffffffff8168381f>] cpufreq_add_dev+0x5f/0x90 [ 22.014717] [<ffffffff81530ac8>] subsys_interface_register+0xb8/0x100 [ 22.014719] [<ffffffff816821bc>] cpufreq_register_driver+0x14c/0x210 [ 22.014749] [<ffffffff81fe1d90>] intel_pstate_init+0x39d/0x4d5 [ 22.014751] [<ffffffff81fe13f2>] ? cpufreq_gov_dbs_init+0x12/0x12 Cc: 4.3+ <stable@vger.kernel.org> # 4.3+ Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/intel_pstate.c10
1 files changed, 5 insertions, 5 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 806f2039571e..bc976a3db253 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -562,12 +562,12 @@ static void intel_pstate_hwp_set(const struct cpumask *cpumask)
int min, hw_min, max, hw_max, cpu, range, adj_range;
u64 value, cap;
- rdmsrl(MSR_HWP_CAPABILITIES, cap);
- hw_min = HWP_LOWEST_PERF(cap);
- hw_max = HWP_HIGHEST_PERF(cap);
- range = hw_max - hw_min;
-
for_each_cpu(cpu, cpumask) {
+ rdmsrl_on_cpu(cpu, MSR_HWP_CAPABILITIES, &cap);
+ hw_min = HWP_LOWEST_PERF(cap);
+ hw_max = HWP_HIGHEST_PERF(cap);
+ range = hw_max - hw_min;
+
rdmsrl_on_cpu(cpu, MSR_HWP_REQUEST, &value);
adj_range = limits->min_perf_pct * range / 100;
min = hw_min + adj_range;