[PATCH 08/12] powerpc/pseries/svm: Export guest SVM status to user space via sysfs

Thiago Jung Bauermann
2019-05-21T04:53:17Z

From: Ryan Grimm <grimm@linux.vnet.ibm.com>

User space might want to know it's running in a secure VM. It can't do
a mfmsr because mfmsr is a privileged instruction.

The solution here is to create a cpu attribute:

/sys/devices/system/cpu/svm

which will read 0 or 1 based on the S bit of the guest's CPU 0.

Signed-off-by: Ryan Grimm <grimm@linux.vnet.ibm.com>
Reviewed-by: Ram Pai <linuxram@us.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
arch/powerpc/kernel/sysfs.c | 29 +++++++++++++++++++++++++++++
1 file changed, 29 insertions(+)

diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index e8e93c2c7d03..8fdab134e9ae 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -18,6 +18,7 @@
#include <asm/smp.h>
#include <asm/pmc.h>
#include <asm/firmware.h>
+#include <asm/svm.h>

#include "cacheinfo.h"
#include "setup.h"
@@ -714,6 +715,32 @@ static struct device_attribute pa6t_attrs[] = {
#endif /* HAS_PPC_PMC_PA6T */
#endif /* HAS_PPC_PMC_CLASSIC */

+#ifdef CONFIG_PPC_SVM
+static void get_svm(void *val)
+{
+ u32 *value = val;
+
+ *value = is_secure_guest();
+}
+
+static ssize_t show_svm(struct device *dev, struct device_attribute *attr, char *buf)
+{
+ u32 val;
+ smp_call_function_single(0, get_svm, &val, 1);
+ return sprintf(buf, "%u\n", val);
+}
+static DEVICE_ATTR(svm, 0444, show_svm, NULL);
+
+static void create_svm_file(void)
+{
+ device_create_file(cpu_subsys.dev_root, &dev_attr_svm);
+}
+#else
+static void create_svm_file(void)
+{
+}
+#endif /* CONFIG_PPC_SVM */
+
static int register_cpu_online(unsigned int cpu)
{
struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -1057,6 +1084,8 @@ static int __init topology_init(void)
sysfs_create_dscr_default();
#endif /* CONFIG_PPC64 */

+ create_svm_file();
+
return 0;
}
subsys_initcall(topology_init);