Commit 734560ac authored by Ryan Grimm's avatar Ryan Grimm Committed by Michael Ellerman
Browse files

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: default avatarRyan Grimm <grimm@linux.vnet.ibm.com>
Signed-off-by: default avatarThiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190820021326.6884-12-bauerman@linux.ibm.com
parent 256ba2c1

Documentation/ABI/testing/sysfs-devices-system-cpu

+10 −0
Original line number Diff line number Diff line
@@ -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.

arch/powerpc/kernel/sysfs.c

+20 −0
Original line number Diff line number Diff line
@@ -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);

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