Michael Ellerman <m...@ellerman.id.au> writes:
> Thiago Jung Bauermann <bauer...@linux.ibm.com> writes:
>> From: Ryan Grimm <gr...@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.
>
> Why CPU 0?
>
> If we have different CPUs running with different MSR_S then something
> has gone badly wrong, no?
Yes, that would be very bad.
> So can't we just read the MSR on whatever CPU the sysfs code happens to
> run on.
Good point. I made the change in the patch below.
--
Thiago Jung Bauermann
IBM Linux Technology Center
>From 2d951305e118bf286f8e83cbf396448085186357 Mon Sep 17 00:00:00 2001
From: Ryan Grimm <gr...@linux.vnet.ibm.com>
Date: Tue, 15 Jan 2019 11:56:29 -0600
Subject: [PATCH] powerpc/pseries/svm: Export guest SVM status to user space
via sysfs
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 current CPU.
Signed-off-by: Ryan Grimm <gr...@linux.vnet.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauer...@linux.ibm.com>
---
arch/powerpc/kernel/sysfs.c | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index e2147d7c9e72..80a676da11cb 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -19,6 +19,7 @@
#include <asm/smp.h>
#include <asm/pmc.h>
#include <asm/firmware.h>
+#include <asm/svm.h>
#include "cacheinfo.h"
#include "setup.h"
@@ -715,6 +716,23 @@ static struct device_attribute pa6t_attrs[] = {
#endif /* HAS_PPC_PMC_PA6T */
#endif /* HAS_PPC_PMC_CLASSIC */
+#ifdef CONFIG_PPC_SVM
+static ssize_t show_svm(struct device *dev, struct device_attribute *attr,
char *buf)
+{
+ return sprintf(buf, "%u\n", is_secure_guest());
+}
+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);
@@ -1058,6 +1076,8 @@ static int __init topology_init(void)
sysfs_create_dscr_default();
#endif /* CONFIG_PPC64 */
+ create_svm_file();
+
return 0;
}
subsys_initcall(topology_init);
