linux-kernel - Re: [PATCH v3 08/16] powerpc/pseries/svm: Use shared memory for LPPACA structures

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Date:   Wed, 14 Aug 2019 20:54:12 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Anshuman Khandual <anshuman.linux@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christoph Hellwig <hch@....de>,
        Mike Anderson <andmike@...ux.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Ram Pai <linuxram@...ibm.com>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>
Subject: Re: [PATCH v3 08/16] powerpc/pseries/svm: Use shared memory for LPPACA structures

Thiago Jung Bauermann <bauerman@...ux.ibm.com> writes:
> Michael Ellerman <mpe@...erman.id.au> writes:
>> Thiago Jung Bauermann <bauerman@...ux.ibm.com> writes:
>>> From: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
>>>
>>> LPPACA structures need to be shared with the host. Hence they need to be in
>>> shared memory. Instead of allocating individual chunks of memory for a
>>> given structure from memblock, a contiguous chunk of memory is allocated
>>> and then converted into shared memory. Subsequent allocation requests will
>>> come from the contiguous chunk which will be always shared memory for all
>>> structures.
>>>
>>> While we are able to use a kmem_cache constructor for the Debug Trace Log,
>>> LPPACAs are allocated very early in the boot process (before SLUB is
>>> available) so we need to use a simpler scheme here.
>>>
>>> Introduce helper is_svm_platform() which uses the S bit of the MSR to tell
>>> whether we're running as a secure guest.
>>>
>>> Signed-off-by: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
>>> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
>>> ---
>>>  arch/powerpc/include/asm/svm.h | 26 ++++++++++++++++++++
>>>  arch/powerpc/kernel/paca.c     | 43 +++++++++++++++++++++++++++++++++-
>>>  2 files changed, 68 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
>>> new file mode 100644
>>> index 000000000000..fef3740f46a6
>>> --- /dev/null
>>> +++ b/arch/powerpc/include/asm/svm.h
>>> @@ -0,0 +1,26 @@
>>> +/* SPDX-License-Identifier: GPL-2.0+ */
>>> +/*
>>> + * SVM helper functions
>>> + *
>>> + * Copyright 2019 Anshuman Khandual, IBM Corporation.
>>
>> Are we sure this copyright date is correct?
>
> I may be confused about which year the copyright refers to. I thought it
> was the year when the patch was committed. If it is the first time the
> patch was published then this one should be 2018.

I'm not a lawyer etc. but AIUI the date above is about the authorship,
ie. when it was originally written, not when it was published or
committed.

In general I don't think it matters too much, but in this case I'm
pretty sure Anshuman can't have possibly written it in 2019 on behalf of
IBM :)

So we can either change the date to 2018, or drop his name and just say
it's copyright 2019 by IBM.

cheers