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

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Date:   Mon, 12 Aug 2019 18:43:45 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
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>
Subject: Re: [PATCH v3 08/16] powerpc/pseries/svm: Use shared memory for LPPACA structures


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.

--
Thiago Jung Bauermann
IBM Linux Technology Center