[tip:core/smp] dcdbas: Make use of smp_call_on_cpu()

[tip-bot for Juergen Gross <tipbot@xxxxxxxxx>]

Commit-ID:  e23f22b5cb9e44da24cb8494707536211adff8d1
Gitweb:     http://git.kernel.org/tip/e23f22b5cb9e44da24cb8494707536211adff8d1
Author:     Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Mon, 29 Aug 2016 08:48:46 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 5 Sep 2016 13:52:40 +0200

dcdbas: Make use of smp_call_on_cpu()

Use smp_call_on_cpu() to raise SMI on CPU 0.
Make call secure by adding get_online_cpus() to avoid e.g. suspend
resume cycles in between.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Douglas_Warzecha@xxxxxxxx
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: akataria@xxxxxxxxxx
Cc: boris.ostrovsky@xxxxxxxxxx
Cc: chrisw@xxxxxxxxxxxx
Cc: david.vrabel@xxxxxxxxxx
Cc: hpa@xxxxxxxxx
Cc: jdelvare@xxxxxxxx
Cc: jeremy@xxxxxxxx
Cc: linux@xxxxxxxxxxxx
Cc: pali.rohar@xxxxxxxxx
Cc: rusty@xxxxxxxxxxxxxxx
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1472453327-19050-6-git-send-email-jgross@xxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 drivers/firmware/dcdbas.c | 51 ++++++++++++++++++++++++-----------------------
 1 file changed, 26 insertions(+), 25 deletions(-)

diff --git a/drivers/firmware/dcdbas.c b/drivers/firmware/dcdbas.c
index 829eec8..2fe1a13 100644
--- a/drivers/firmware/dcdbas.c
+++ b/drivers/firmware/dcdbas.c
@@ -23,6 +23,7 @@
 #include <linux/platform_device.h>
 #include <linux/dma-mapping.h>
 #include <linux/errno.h>
+#include <linux/cpu.h>
 #include <linux/gfp.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -238,33 +239,14 @@ static ssize_t host_control_on_shutdown_store(struct device *dev,
 	return count;
 }
 
-/**
- * dcdbas_smi_request: generate SMI request
- *
- * Called with smi_data_lock.
- */
-int dcdbas_smi_request(struct smi_cmd *smi_cmd)
+static int raise_smi(void *par)
 {
-	cpumask_var_t old_mask;
-	int ret = 0;
-
-	if (smi_cmd->magic != SMI_CMD_MAGIC) {
-		dev_info(&dcdbas_pdev->dev, "%s: invalid magic value\n",
-			 __func__);
-		return -EBADR;
-	}
+	struct smi_cmd *smi_cmd = par;
 
-	/* SMI 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) {
 		dev_dbg(&dcdbas_pdev->dev, "%s: failed to get CPU 0\n",
 			__func__);
-		ret = -EBUSY;
-		goto out;
+		return -EBUSY;
 	}
 
 	/* generate SMI */
@@ -280,9 +262,28 @@ int dcdbas_smi_request(struct smi_cmd *smi_cmd)
 		: "memory"
 	);
 
-out:
-	set_cpus_allowed_ptr(current, old_mask);
-	free_cpumask_var(old_mask);
+	return 0;
+}
+/**
+ * dcdbas_smi_request: generate SMI request
+ *
+ * Called with smi_data_lock.
+ */
+int dcdbas_smi_request(struct smi_cmd *smi_cmd)
+{
+	int ret;
+
+	if (smi_cmd->magic != SMI_CMD_MAGIC) {
+		dev_info(&dcdbas_pdev->dev, "%s: invalid magic value\n",
+			 __func__);
+		return -EBADR;
+	}
+
+	/* SMI requires CPU 0 */
+	get_online_cpus();
+	ret = smp_call_on_cpu(0, raise_smi, smi_cmd, true);
+	put_online_cpus();
+
 	return ret;
 }
 
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