Re: [Qemu-devel] subpage_write() and duplicated memory_region_ops_write tracepoints

[Paolo Bonzini]

On 09/12/2015 21:54, Hollis Blanchard wrote:
> 
> #0  trace_memory_region_ops_write (mr=0x185b620, addr=16, absaddr=738205712, 
> value=136, size=4)
>     at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/trace/generated-tracers.h:7374
> #1  0x000000000045eb8a in *memory_region_write_with_attrs_accessor* 
> (mr=0x185b620, addr=16, 
>     value=0x45203338, size=4, shift=0, mask=4294967295, attrs=...)
>     at /scratch1/hblancha/install/customq/qemu-2.4.0/src/memory.c:513
> #2  0x000000000045ed08 in access_with_adjusted_size (addr=16, 
> value=0x45203338, size=4, 
>     access_size_min=1, access_size_max=4, access=0x45eb15 
> <memory_region_write_with_attrs_accessor>, 
>     mr=0x185b620, attrs=...) at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/memory.c:556
> #3  0x0000000000461ed7 in memory_region_dispatch_write (mr=0x185b620, 
> addr=16, data=136, size=4, 
>     attrs=...) at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/memory.c:1214
> #4  0x0000000000411bbf in address_space_rw (as=0x11f3440, addr=738205712, 
> attrs=..., 
>     buf=0x45203490 "\210", len=4, is_write=true)
>     at /scratch1/hblancha/install/customq/qemu-2.4.0/src/exec.c:2497
> #5  0x0000000000411ea9 in address_space_write (as=0x11f3440, addr=738205712, 
> attrs=..., 
>     buf=0x45203490 "\210", len=4) at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/exec.c:2579
> #6  0x0000000000410d89 in subpage_write (opaque=0x19148f0, addr=16, 
> value=136, len=4, attrs=...)
>     at /scratch1/hblancha/install/customq/qemu-2.4.0/src/exec.c:2139
> #7  0x000000000045ebb2 in *memory_region_write_with_attrs_accessor* 
> (mr=0x19148f0, addr=16, 
>     value=0x452035a8, size=4, shift=0, mask=4294967295, attrs=...)
>     at /scratch1/hblancha/install/customq/qemu-2.4.0/src/memory.c:516
> #8  0x000000000045ed08 in access_with_adjusted_size (addr=16, 
> value=0x452035a8, size=4, 
>     access_size_min=1, access_size_max=8, access=0x45eb15 
> <memory_region_write_with_attrs_accessor>, 
>     mr=0x19148f0, attrs=...) at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/memory.c:556
> #9  0x0000000000461ed7 in memory_region_dispatch_write (mr=0x19148f0, 
> addr=16, data=136, size=4, 
>     attrs=...) at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/memory.c:1214
> #10 0x000000000046c61c in io_writel (env=0x2aabace89268, 
> iotlbentry=0x2aabace99808, val=136, 
>     addr=18446743523953745936, retaddr=1107508028)
>     at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/softmmu_template.h:470
> #11 0x000000000046c3cb in helper_le_stl_mmu (env=0x2aabace89268, 
> addr=18446743523953745936, val=136, 
>     oi=33, retaddr=1107508028)
>     at 
> /scratch1/hblancha/install/customq/qemu-2.4.0/src/softmmu_template.h:510
> #12 0x0000000042033b3e in code_gen_buffer ()
> 
> 
> The first tracepoint in each pair is an artifact, and should be omitted.
> Any suggestions? We could special case "if (mr->ops->write !=
> subpage_write) { emit tracepoint }", but that's a bit of a hack... :-)

You can add an argument to the tracepoint for mr->subpage.  I would keep
the duplicate however.

Paolo