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authorGuenter Roeck <linux@roeck-us.net>2013-12-14 09:30:15 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-18 16:45:38 -0800
commitf36fdb9f0266811ee27140acc6ac5ff21199b159 (patch)
treedb55e44e0d29792be1f0ebba9e92939e54d4d8a6 /drivers/char/i8k.c
parent14d32383965243ea37f00656538d91a2ea3a719f (diff)
i8k: Force SMM to run on CPU 0
On Studio 1555 with dual-core CPU, reading sensor attributes exported by this driver resulted in random failures combined with system hangups and forced logouts. Information in drivers/firmware/dcdbas.c suggests that SMM accesses must run on CPU 0. With this patch, the problems are gone, suggesting that this is in fact the case. Code derived from drivers/firmware/dcdbas.c. Cc: Jean Delvare <khali@linux-fr.org> Signed-off-by: Guenter Roeck <linux@roeck-us.net> Acked-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char/i8k.c')
-rw-r--r--drivers/char/i8k.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
index 7e31e47ef987..f24bbcd848de 100644
--- a/drivers/char/i8k.c
+++ b/drivers/char/i8k.c
@@ -31,6 +31,7 @@
#include <linux/hwmon-sysfs.h>
#include <linux/uaccess.h>
#include <linux/io.h>
+#include <linux/sched.h>
#include <linux/i8k.h>
@@ -130,6 +131,17 @@ static int i8k_smm(struct smm_regs *regs)
{
int rc;
int eax = regs->eax;
+ cpumask_var_t old_mask;
+
+ /* SMM requires CPU 0 */
+ if (!alloc_cpumask_var(&old_mask, GFP_KERNEL))
+ return -ENOMEM;
+ cpumask_copy(old_mask, &current->cpus_allowed);
+ set_cpus_allowed_ptr(current, cpumask_of(0));
+ if (smp_processor_id() != 0) {
+ rc = -EBUSY;
+ goto out;
+ }
#if defined(CONFIG_X86_64)
asm volatile("pushq %%rax\n\t"
@@ -185,9 +197,12 @@ static int i8k_smm(struct smm_regs *regs)
: "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory");
#endif
if (rc != 0 || (regs->eax & 0xffff) == 0xffff || regs->eax == eax)
- return -EINVAL;
+ rc = -EINVAL;
- return 0;
+out:
+ set_cpus_allowed_ptr(current, old_mask);
+ free_cpumask_var(old_mask);
+ return rc;
}
/*