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Subject: Re: [PATCH v3 15/15] powerpc/32s: Activate CONFIG_VMAP_STACK
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>, npiggin@gmail.com,
        dja@axtens.net
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
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References: <cover.1568106758.git.christophe.leroy@c-s.fr>
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 <875zjgcpyx.fsf@mpe.ellerman.id.au>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <f3074852-ef83-5426-9928-f0201f704b49@c-s.fr>
Date:   Tue, 26 Nov 2019 10:01:22 +0100
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Le 19/11/2019 à 07:58, Michael Ellerman a écrit :
> Christophe Leroy <christophe.leroy@c-s.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@c-s.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(-)
> 
> This is faulting with qemu mac99 model:
> 
>    Key type id_resolver registered
>    Key type id_legacy registered
>    BUG: Unable to handle kernel data access on read at 0x2f0db684
>    Faulting instruction address: 0x00004130
>    Oops: Kernel access of bad area, sig: 11 [#1]
>    BE PAGE_SIZE=4K MMU=Hash PowerMac
>    Modules linked in:
>    CPU: 0 PID: 65 Comm: modprobe Not tainted 5.4.0-rc2-gcc49+ #63
>    NIP:  00004130 LR: 000008c8 CTR: b7eb86e0

Problem found, that's in load_up_fpu(), have to apply tovirt() to the 
address read from SPRN_SPRG_THREAD. Same problem in load_up_altivec().
I'll fix that in v4 today.

Christophe