powerpc/kernel/sysfs.c exports purr with write permission.
This is only valid for kernel in hypervisor mode.
But writing to the file in PowerVM lpar causes crash.
# echo 0 > purr
cpu 0x0: Vector: 700 (Program Check) at [c000000000d072b0]
pc: c00000000001770c: .write_purr+0x1c/0x40
lr: c000000000017708: .write_purr+0x18/0x40
sp: c000000000d07530
msr: 8000000000049032
current = 0xc000000000c53de0
paca = 0xc00000000ec70000 softe: 0 irq_happened: 0x01
pid = 0, comm = swapper/0
enter ? for help
[c000000000d075b0] c0000000000fba64
.generic_smp_call_function_single_interrupt+0x104/0x190
[c000000000d07650] c000000000037748 .smp_ipi_demux+0xa8/0xf0
[c000000000d076e0] c000000000035314 .doorbell_exception+0x74/0xb0
[c000000000d07760] c000000000002950 doorbell_super_common+0x150/0x180
--- Exception: a01 (Doorbell) at c000000000060904
.plpar_hcall_norets+0x84/0xd4
[link register ] c00000000006dbd4 .check_and_cede_processor+0x24/0x40
[c000000000d07a50] c000000001002558 (unreliable)
[c000000000d07ac0] c00000000006dd0c .shared_cede_loop+0x2c/0x70
[c000000000d07b40] c0000000006ae954 .cpuidle_enter_state+0x64/0x150
[c000000000d07c00] c0000000006aeb30 .cpuidle_idle_call+0xf0/0x300
[c000000000d07cb0] c000000000062fa0 .pseries_lpar_idle+0x10/0x50
[c000000000d07d20] c000000000016d14 .arch_cpu_idle+0x64/0x150
[c000000000d07da0] c0000000000e0060 .cpu_startup_entry+0x1a0/0x2c0
[c000000000d07e80] c00000000000bca4 .rest_init+0x94/0xb0
[c000000000d07ef0] c000000000b54530 .start_kernel+0x478/0x494
[c000000000d07f90] c000000000009be0 .start_here_common+0x20/0x40
0:mon>
Changes:
1)Changed the test for to hypervisor mode instead of platform
Signed-off-by: Madhavan Srinivasan <ma...@linux.vnet.ibm.com>
---
arch/powerpc/kernel/sysfs.c | 20 ++++++++++++++++++--
1 file changed, 18 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 27a90b9..42becfa 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -17,6 +17,7 @@
#include <asm/machdep.h>
#include <asm/smp.h>
#include <asm/pmc.h>
+#include <asm/reg.h>
#include "cacheinfo.h"
@@ -179,15 +180,27 @@ SYSFS_PMCSETUP(spurr, SPRN_SPURR);
SYSFS_PMCSETUP(dscr, SPRN_DSCR);
SYSFS_PMCSETUP(pir, SPRN_PIR);
+/*
+ Lets only enable Read for Hyp resources and
+ enable Write when needed with a separate function.
+ Lets be conservative and default to pseries.
+*/
static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
static DEVICE_ATTR(spurr, 0400, show_spurr, NULL);
static DEVICE_ATTR(dscr, 0600, show_dscr, store_dscr);
-static DEVICE_ATTR(purr, 0600, show_purr, store_purr);
+static DEVICE_ATTR(purr, 0400, show_purr, store_purr);
static DEVICE_ATTR(pir, 0400, show_pir, NULL);
unsigned long dscr_default = 0;
EXPORT_SYMBOL(dscr_default);
+static void add_write_permission_dev_attr(void *ptr)
+{
+ struct device_attribute *attr = (struct device_attribute *)ptr;
+
+ attr->attr.mode |= (unsigned short) 0200;
+}
+
static ssize_t show_dscr_default(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -394,8 +407,11 @@ static void register_cpu_online(unsigned int cpu)
if (cpu_has_feature(CPU_FTR_MMCRA))
device_create_file(s, &dev_attr_mmcra);
- if (cpu_has_feature(CPU_FTR_PURR))
+ if (cpu_has_feature(CPU_FTR_PURR)) {
+ if (mfmsr() & MSR_HV)
+ add_write_permission_dev_attr((void *)&dev_attr_purr);
device_create_file(s, &dev_attr_purr);
+ }
if (cpu_has_feature(CPU_FTR_SPURR))
device_create_file(s, &dev_attr_spurr);
--
1.7.10.4
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