Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH] powerpc/8xx: Fix permanently mapped IMMR region.
To:     Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>
Cc:     linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
References: <ad9d45119a48a92bf122781d0c79c9407baa12d7.1566554026.git.christophe.leroy@c-s.fr>
 <87sgmlcu1x.fsf@mpe.ellerman.id.au>
From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <d22ac38c-0b03-fbc0-88d1-899e356fa487@c-s.fr>
Date:   Tue, 26 Nov 2019 08:01:13 +0000
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.7.0
MIME-Version: 1.0
In-Reply-To: <87sgmlcu1x.fsf@mpe.ellerman.id.au>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 11/18/2019 11:17 AM, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@c-s.fr> writes:
>> When not using large TLBs, the IMMR region is still
>> mapped as a whole block in the FIXMAP area.
>>
>> Do not remove pages mapped in the FIXMAP region when
>> initialising paging.
>>
>> Properly report that the IMMR region is block-mapped even
>> when not using large TLBs.
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>>   arch/powerpc/mm/mem.c        |  8 --------
>>   arch/powerpc/mm/nohash/8xx.c | 13 +++++++------
>>   2 files changed, 7 insertions(+), 14 deletions(-)
> 
> This blows up pmac32_defconfig + qemu mac99 for me with:
> 
>    NET: Registered protocol family 1
>    RPC: Registered named UNIX socket transport module.
>    RPC: Registered udp transport module.
>    RPC: Registered tcp transport module.
>    RPC: Registered tcp NFSv4.1 backchannel transport module.
>    PCI: CLS 0 bytes, default 32
>    Trying to unpack rootfs image as initramfs...
>    BUG: Unable to handle kernel data access on write at 0xfffdf000

I tested it with pmac32_defconfig and qemu mac99 and don't get the problem:

NET: Registered protocol family 1
RPC: Registered named UNIX socket transport module.
RPC: Registered udp transport module.
RPC: Registered tcp transport module.
RPC: Registered tcp NFSv4.1 backchannel transport module.
PCI: CLS 0 bytes, default 32
Initialise system trusted keyrings
workingset: timestamp_bits=30 max_order=15 bucket_order=0
NFS: Registering the id_resolver key type
Key type id_resolver registered
...

Looks like I don't get that 'Trying to unpack rootfs image as 
initramfs...', do you change anything to pmac32_defconfig ?

Anyway, when rebasing this patch on next branch, only the 
arch/powerpc/mm/nohash/8xx.c change remains. The other part is already 
applied through another patch.

So I believe the remaining part is safe to apply

Christophe