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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 <grimm@linux.vnet.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190820021326.6884-12-bauerman@linux.ibm.com
This commit is contained in:
Ryan Grimm 2019-08-19 23:13:21 -03:00 committed by Michael Ellerman
parent 256ba2c168
commit 734560ac39
2 changed files with 30 additions and 0 deletions
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10
Documentation/ABI/testing/sysfs-devices-system-cpu
View File

@ -562,3 +562,13 @@ Description: Umwait control
or C0.2 state. The time is an unsigned 32-bit number.
Note that a value of zero means there is no limit.
Low order two bits must be zero.
What: /sys/devices/system/cpu/svm
Date: August 2019
Contact: Linux kernel mailing list <linux-kernel@vger.kernel.org>
Linux for PowerPC mailing list <linuxppc-dev@ozlabs.org>
Description: Secure Virtual Machine
If 1, it means the system is using the Protected Execution
Facility in POWER9 and newer processors. i.e., it is a Secure
Virtual Machine.

20
arch/powerpc/kernel/sysfs.c
View File

@ -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);