[Xen-devel] [PATCH v4 5/6] dcdbas: make use of smp_call_on_cpu()

[Juergen Gross <jgross@xxxxxxxx>]

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>
---
V4: add call to get_online_cpus()
---
 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..68e1d38 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;
+       struct smi_cmd *smi_cmd = par;
 
-       if (smi_cmd->magic != SMI_CMD_MAGIC) {
-               dev_info(&dcdbas_pdev->dev, "%s: invalid magic value\n",
-                        __func__);
-               return -EBADR;
-       }
-
-       /* 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, true, raise_smi, smi_cmd);
+       put_online_cpus();
+
        return ret;
 }
 
-- 
2.6.2


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