linux-kernel - Re: [PATCH v3 15/15] powerpc/32s: Activate CONFIG_VMAP

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Date:   Tue, 19 Nov 2019 18:23:10 +0100
From:   Christophe Leroy <christophe.leroy@....fr>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, dja@...ens.net, npiggin@...il.com,
        Paul Mackerras <paulus@...ba.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH v3 15/15] powerpc/32s: Activate CONFIG_VMAP_STACK

Michael Ellerman <mpe@...erman.id.au> a écrit :

> Christophe Leroy <christophe.leroy@....fr> writes:
>> A few changes to retrieve DAR and DSISR from struct regs
>> instead of retrieving them directly, as they may have
>> changed due to a TLB miss.
>>
>> Also modifies hash_page() and friends to work with virtual
>> data addresses instead of physical ones.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
>> ---
>>  arch/powerpc/kernel/entry_32.S         |  4 +++
>>  arch/powerpc/kernel/head_32.S          | 19 +++++++++++---
>>  arch/powerpc/kernel/head_32.h          |  4 ++-
>>  arch/powerpc/mm/book3s32/hash_low.S    | 46  
>> +++++++++++++++++++++-------------
>>  arch/powerpc/mm/book3s32/mmu.c         |  9 +++++--
>>  arch/powerpc/platforms/Kconfig.cputype |  2 ++
>>  6 files changed, 61 insertions(+), 23 deletions(-)
>
> If I build pmac32_defconfig with KVM enabled this causes a build break:
>
>   arch/powerpc/kernel/head_32.S: Assembler messages:
>   arch/powerpc/kernel/head_32.S:324: Error: attempt to move .org backwards
>   scripts/Makefile.build:357: recipe for target  
> 'arch/powerpc/kernel/head_32.o' failed
>   make[2]: *** [arch/powerpc/kernel/head_32.o] Error 1
>
> In the interests of getting the series merged I'm inclined to just make
> VMAP_STACK and KVM incompatible for now with:
>
> diff --git a/arch/powerpc/platforms/Kconfig.cputype  
> b/arch/powerpc/platforms/Kconfig.cputype
> index 15c9097dc4f7..5074fe77af40 100644
> --- a/arch/powerpc/platforms/Kconfig.cputype
> +++ b/arch/powerpc/platforms/Kconfig.cputype
> @@ -31,7 +31,7 @@ config PPC_BOOK3S_6xx
>         select PPC_HAVE_PMU_SUPPORT
>         select PPC_HAVE_KUEP
>         select PPC_HAVE_KUAP
> -       select HAVE_ARCH_VMAP_STACK
> +       select HAVE_ARCH_VMAP_STACK if !KVM_BOOK3S_32
>
>  config PPC_BOOK3S_601
>         bool "PowerPC 601"
>
>
> Thoughts?

Ok, lets do it the way you propose.

I'll look at this problem with KVM when I'm back next week.

Thanks
Christophe