i8k: Force SMM to run on CPU 0 (f36fdb9f) · Commits · 戴 / test

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>

drivers/char/i8k.c

+17 −2

Original line number	Diff line number	Diff line
		@@ -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;
		}

		/*

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