Re: [Qemu-devel] [Question]Support of China loogson processor

[Leon Alrae <leon.alrae@imgtec.com>]

On 16/04/2015 13:02, Paolo Bonzini wrote:
> 
> 
> On 16/04/2015 13:07, Leon Alrae wrote:
>> Since I also haven't had a chance to test Loongson emulation, I thought
>> I'd give it a try (TCG only, Loongson-2E cpu and fulong2e machine).
>>
>> Good news is that I'm able to get to the login prompt using ancient QEMU
>> v1.0, kernel 2.6.33 (with additional patch from
>> https://lists.gnu.org/archive/html/qemu-devel/2010-06/msg02566.html) and
>> some old debian image I had handy. However, in any newer version
>> starting from v1.1.0 of QEMU something goes horribly wrong and it just
>> segfaults somewhere inside hw/bonito.c quite early during kernel
>> booting.
> 
> Where exactly?  If it's related to the memory API conversion, it may be
> easy to fix.  I can look at a backtrace (or you can just put the Debian
> image somewhere I can grab it).

Bisect points at: 5312bd8b3152f8d4fcf9389ba54e32b09f4b4093

Crash occurs during the first access, below there is backtrace from
working and not working case:

Bad:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffefe27700 (LWP 10929)]
0x00005555557a2278 in bonito_readl (opaque=0x5555564fb690, addr=24, size=4) at qemu/hw/bonito.c:299
299             return s->regs[saddr];
(gdb) bt
#0  0x00005555557a2278 in bonito_readl (opaque=0x5555564fb690, addr=24, size=4) at qemu/hw/bonito.c:299
#1  0x00005555557d6e03 in memory_region_read_accessor (opaque=0x5555564fbb60, addr=24, value=0x7fffefe265d0, size=4, shift=0, mask=4294967295) at qemu/memory.c:314
#2  0x00005555557d6fa9 in access_with_adjusted_size (addr=24, value=0x7fffefe265d0, size=4, access_size_min=1, access_size_max=4, access=0x5555557d6daa <memory_region_read_accessor>, opaque=0x5555564fbb60) at qemu/memory.c:359
#3  0x00005555557d9796 in memory_region_dispatch_read1 (mr=0x5555564fbb60, addr=24, size=4) at qemu/memory.c:860
#4  0x00005555557d9886 in memory_region_dispatch_read (mr=0x5555564fbb60, addr=24, size=4) at qemu/memory.c:892
#5  0x00005555557dc306 in io_mem_read (io_index=6, addr=24, size=4) at qemu/memory.c:1492
#6  0x00005555557aed0d in subpage_read (opaque=0x5555564ed790, addr=24, len=4) at qemu/exec.c:3351
#7  0x00005555557d6e03 in memory_region_read_accessor (opaque=0x5555564ed790, addr=280, value=0x7fffefe267d0, size=4, shift=0, mask=4294967295) at qemu/memory.c:314
#8  0x00005555557d6fa9 in access_with_adjusted_size (addr=280, value=0x7fffefe267d0, size=4, access_size_min=1, access_size_max=4, access=0x5555557d6daa <memory_region_read_accessor>, opaque=0x5555564ed790) at qemu/memory.c:359
#9  0x00005555557d9796 in memory_region_dispatch_read1 (mr=0x5555564ed790, addr=280, size=4) at qemu/memory.c:860
#10 0x00005555557d9886 in memory_region_dispatch_read (mr=0x5555564ed790, addr=280, size=4) at qemu/memory.c:892
#11 0x00005555557dc306 in io_mem_read (io_index=7, addr=280, size=4) at qemu/memory.c:1492
#12 0x00005555557f523e in io_readl (physaddr=280, addr=18446744072633712920, retaddr=0x4023335e) at qemu/softmmu_template.h:78
#13 0x00005555557f5335 in __ldl_mmu (addr=18446744072633712920, mmu_idx=0) at qemu/softmmu_template.h:114


Good:

Breakpoint 1, bonito_readl (opaque=0x55555646e450, addr=280, size=4) at qemu/hw/bonito.c:288
288     {
(gdb) bt
#0  bonito_readl (opaque=0x55555646e450, addr=280, size=4) at qemu/hw/bonito.c:288
#1  0x00005555557d6b83 in memory_region_read_accessor (opaque=0x55555646e920, addr=280, value=0x7fffefe265d0, size=4, shift=0, mask=4294967295) at qemu/memory.c:314
#2  0x00005555557d6d29 in access_with_adjusted_size (addr=280, value=0x7fffefe265d0, size=4, access_size_min=1, access_size_max=4, access=0x5555557d6b2a <memory_region_read_accessor>, opaque=0x55555646e920) at qemu/memory.c:359
#3  0x00005555557d9516 in memory_region_dispatch_read1 (mr=0x55555646e920, addr=280, size=4) at qemu/memory.c:860
#4  0x00005555557d9606 in memory_region_dispatch_read (mr=0x55555646e920, addr=280, size=4) at qemu/memory.c:892
#5  0x00005555557dc086 in io_mem_read (io_index=6, addr=280, size=4) at qemu/memory.c:1492
#6  0x00005555557aeba5 in subpage_read (opaque=0x555556543730, addr=280, len=4) at qemu/exec.c:3343
#7  0x00005555557d6b83 in memory_region_read_accessor (opaque=0x555556543730, addr=280, value=0x7fffefe267d0, size=4, shift=0, mask=4294967295) at qemu/memory.c:314
#8  0x00005555557d6d29 in access_with_adjusted_size (addr=280, value=0x7fffefe267d0, size=4, access_size_min=1, access_size_max=4, access=0x5555557d6b2a <memory_region_read_accessor>, opaque=0x555556543730) at qemu/memory.c:359
#9  0x00005555557d9516 in memory_region_dispatch_read1 (mr=0x555556543730, addr=280, size=4) at qemu/memory.c:860
#10 0x00005555557d9606 in memory_region_dispatch_read (mr=0x555556543730, addr=280, size=4) at qemu/memory.c:892
#11 0x00005555557dc086 in io_mem_read (io_index=7, addr=280, size=4) at qemu/memory.c:1492
#12 0x00005555557f4fbe in io_readl (physaddr=280, addr=18446744072633712920, retaddr=0x40232bde) at qemu/softmmu_template.h:78
#13 0x00005555557f50b5 in __ldl_mmu (addr=18446744072633712920, mmu_idx=0) at qemu/softmmu_template.h:114