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

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Message-ID: <875zn2sgqs.fsf@concordia.ellerman.id.au>
Date:   Mon, 12 Aug 2019 22:36:11 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     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>,
        Thiago Jung Bauermann <bauerman@...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:
> 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?

cheers