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From: Thiago Jung Bauermann <bauerman@linux.ibm.com>
To: Michael Ellerman <mpe@ellerman.id.au>
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 21:49:26 -0300	[thread overview]
Message-ID: <87imqyrl2h.fsf@morokweng.localdomain> (raw)
In-Reply-To: <87sgq36ivk.fsf@concordia.ellerman.id.au>


Michael Ellerman <mpe@ellerman.id.au> writes:

> 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.

Ok. TBH this patch is not as urgent as the others. It was added so that
tests have an easy way to tell if they're in an SVM. I can leave it out
for now to figure out if there's a better place for this information.

> Still you should document the attribute in Documentation/ABI/testing/sysfs-devices-system-cpu

Indedd, will do that.

--
Thiago Jung Bauermann
IBM Linux Technology Center

  reply	other threads:[~2019-08-16  0:50 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
2019-08-16  0:49         ` Thiago Jung Bauermann [this message]
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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