Messages in this thread Patch in this message | | | From | Thiago Jung Bauermann <> | Subject | Re: [PATCH v3 11/16] powerpc/pseries/svm: Export guest SVM status to user space via sysfs | Date | Mon, 12 Aug 2019 20:21:50 -0300 |
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Michael Ellerman <mpe@ellerman.id.au> writes:
> Thiago Jung Bauermann <bauerman@linux.ibm.com> writes: >> 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. > > 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 <grimm@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 <grimm@linux.vnet.ibm.com> Signed-off-by: Thiago Jung Bauermann <bauerman@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);
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