From: Michael Ellerman <mpe@ellerman.id.au>
To: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
Alexey Kardashevskiy <aik@ozlabs.ru>,
Anshuman Khandual <anshuman.linux@gmail.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Christoph Hellwig <hch@lst.de>,
Mike Anderson <andmike@linux.ibm.com>,
Paul Mackerras <paulus@samba.org>, Ram Pai <linuxram@us.ibm.com>,
Claudio Carvalho <cclaudio@linux.ibm.com>,
Ryan Grimm <grimm@linux.vnet.ibm.com>
Subject: Re: [PATCH v3 11/16] powerpc/pseries/svm: Export guest SVM status to user space via sysfs
Date: Thu, 15 Aug 2019 16:30:07 +1000 [thread overview]
Message-ID: <87sgq36ivk.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <87r25qgeb5.fsf@morokweng.localdomain>
Thiago Jung Bauermann <bauerman@linux.ibm.com> writes:
> 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.
The patch looks good. Although, it raises the question of whether it
should be an attribute of the CPU at all.
I guess there's not obviously anywhere better for it.
Still you should document the attribute in Documentation/ABI/testing/sysfs-devices-system-cpu
cheers
> 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);
next prev parent reply other threads:[~2019-08-15 6:30 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-06 5:22 [PATCH v3 00/16] Secure Virtual Machine Enablement Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 01/16] powerpc/kernel: Add ucall_norets() ultravisor call handler Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 02/16] powerpc/pseries: Introduce option to build secure virtual machines Thiago Jung Bauermann
2019-08-06 5:22 ` [RFC PATCH v3 03/16] powerpc: Add support for adding an ESM blob to the zImage wrapper Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 04/16] powerpc/prom_init: Add the ESM call to prom_init Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 05/16] powerpc/pseries/svm: Add helpers for UV_SHARE_PAGE and UV_UNSHARE_PAGE Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 06/16] powerpc: Introduce the MSR_S bit Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 07/16] powerpc/pseries: Add and use LPPACA_SIZE constant Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 08/16] powerpc/pseries/svm: Use shared memory for LPPACA structures Thiago Jung Bauermann
2019-08-12 12:36 ` Michael Ellerman
2019-08-12 21:43 ` Thiago Jung Bauermann
2019-08-14 10:54 ` Michael Ellerman
2019-08-16 0:52 ` Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 09/16] powerpc/pseries/svm: Use shared memory for Debug Trace Log (DTL) Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 10/16] powerpc/pseries/svm: Unshare all pages before kexecing a new kernel Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 11/16] powerpc/pseries/svm: Export guest SVM status to user space via sysfs Thiago Jung Bauermann
2019-08-12 13:03 ` Michael Ellerman
2019-08-12 23:21 ` Thiago Jung Bauermann
2019-08-15 6:30 ` Michael Ellerman [this message]
2019-08-16 0:49 ` Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 12/16] powerpc/pseries/svm: Disable doorbells in SVM guests Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 13/16] powerpc/pseries/iommu: Don't use dma_iommu_ops on secure guests Thiago Jung Bauermann
2019-08-06 5:48 ` Christoph Hellwig
2019-08-07 1:37 ` Thiago Jung Bauermann
2019-08-06 5:22 ` [PATCH v3 14/16] powerpc/pseries/svm: Force SWIOTLB for " Thiago Jung Bauermann
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