Re: [Qemu-devel] What's the next QEMU version after 2.9 ? (or: when is a good point in time to get rid of old interfaces)

[Philippe Mathieu-Daudé]

Hi Yongbok Kim,

On 03/10/2017 08:58 AM, Yongbok Kim wrote:
> On 10/03/2017 11:53, Thomas Huth wrote:
>> On 10.03.2017 12:22, Peter Maydell wrote:
>>> On 10 March 2017 at 12:07, Jason Wang <address@hidden> wrote:
>>>> On 2017年03月09日 18:20, Yongbok Kim wrote:
>>>>> Indeed but we still use the platform to verify architectural
>>>>> compatibilities even for newer MIPS architectures.
>>>
>>>> I see, but I believe it may need some modifications in the code to support
>>>> newer architectures? If yes, plan to send them upstream? Since it has been
>>>> deprecated, if no new codes it makes sense to deprecate it in qemu too. You
>>>> can still use exist qemu versions to do the verification.
>>>
>>> Taking a step back, the reason for deprecating and deleting
>>> code is to avoid having unmaintained and unused code in QEMU.
>>> If Yongbok is maintaining the mipssim board and devices
>>> and is willing to keep them up to spec with current QOM
>>> and other best practices, and there are test images to
>>> check they still work, I think that's fine.
>>
>> But the Mipssim machine is currently marked as "Orphan" in our
>> MAINTAINERS file ... Yongbok, if you're still using it, would you maybe
>> be interested in doing at least "Odd fixes" here?
>> BTW, I think "F: hw/net/mipsnet.c" should be added to the "Mipssim"
>> section, too.
>>
> Yes I am willing to maintain the machine. I will post a patch to the
> MAINTAINERS file for the machine and other MIPS machines.

I'm trying to setup Avocado [1] VM tests on Unsupported machines from
the MAINTAINERS file, which include the "Odd Fixes" status entry.

Do you have images I can use for the MIPSsim board? It has been very
hard to reproduce some.

- Linux dropped MIPSsim support in v3.18

- I checkouted longterm v3.2.101 kernel, then hit:

$ make mipssim_defconfig
$ make vmlinux
include/linux/compiler-gcc.h:105:30:
fatal error: linux/compiler-gcc6.h: No such file or directory

I backported include/linux/compiler-gcc.h from long term stable
v3.16.56, but then:

  AS      arch/mips/kernel/r4k_fpu.o

arch/mips/kernel/r4k_fpu.S: Assembler messages:

arch/mips/kernel/r4k_fpu.S:59: Error: opcode not supported on this
processor: mips3 (mips3) `sdc1 $f0,272+0($4)'

which is a binutils problem.

After reading https://lkml.org/lkml/2015/7/15/26, I backported commit
842dfc11ea9a2 but then hitting other problems I gave out and started a
different approach.

- I checkouted the more recent long term stable v3.16.56 kernel and
reverted commits b30fdd6f7395b and 270690e00cdb0.

I then could rebuild a kernel for this board.

You can find the signed tag I'll use for the Avocado tests here:
https://github.com/philmd/linux/releases/tag/linux-mipssim-3.16.56

So far this kernel doesn't boot far, but at least I could test the
console is working:

$ ./mipsel-softmmu/qemu-system-mipsel -M mipssim -kernel
/build/linux/mipssim/vmlinux -nographic
Linux version 3.16.56-00002-g41a1a4f084a9 (address@hidden) (gcc version 6.3.0
20170516 (Debian 6.3.0-18) ) #1 Tue Apr 24 15:20:39 -03 2018
Setting default memory size 0x02000000
bootconsole [early0] enabled
CPU0 revision is: 00019300 (MIPS 24Kc)
FPU revision is: 00739300
...
CPU frequency 12.00 MHz
random: nonblocking pool is initialized
CPU 0 Unable to handle kernel paging request at virtual address
00000080, epc == 80132d9c, ra == 801330a0
Oops[#1]:
CPU: 0 PID: 0 Comm: swapper Not tainted 3.16.56-00002-g41a1a4f084a9 #1
Call Trace:
[<80132d9c>] __queue_work+0x3c/0x2b8
[<801330a0>] queue_work_on+0x88/0xb4
[<8029df08>] credit_entropy_bits+0x21c/0x300
[<8015239c>] handle_irq_event_percpu+0xc8/0x1a0
[<80155ac8>] handle_percpu_irq+0x54/0x84
[<80151ac8>] generic_handle_irq+0x34/0x4c
[<801056c0>] do_IRQ+0x18/0x28
[<80103628>] ret_from_irq+0x0/0x4
[<80120d80>] __do_softirq+0xc0/0x2dc
[<80121290>] irq_exit+0x90/0x98
[<80103628>] ret_from_irq+0x0/0x4
[<8040ca48>] start_kernel+0x2e4/0x3e4

My setup is a Debian/Sid with mipsel-linux-gnu-gcc (GCC 6.3),
I also used the following shell environment:

$ export CROSS_COMPILE=mips-linux-gnu- ARCH=mips

Regards,

Phil.

[1] http://lists.nongnu.org/archive/html/qemu-devel/2018-04/msg03355.html

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