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

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Date:   Mon, 18 Nov 2019 22:11:38 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@....fr>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>, npiggin@...il.com,
        dja@...ens.net
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-mm@...ck.org
Subject: Re: [PATCH v3 15/15] powerpc/32s: Activate CONFIG_VMAP_STACK

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?

cheers