Re: [PATCH 0/7] plugins: Use unwind info for special gdb registers

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 4/15/24 21:06, Richard Henderson wrote:
> Based-on: 20240404230611.21231-1-richard.henderson@linaro.org
> ("[PATCH v2 00/21] Rewrite plugin code generation")
> 
> This is an attempt to fix
> https://gitlab.com/qemu-project/qemu/-/issues/2208
> ("PC is not updated for each instruction in TCG plugins")
> 
> I have only updated target/i386 so far, but basically all targets
> need updating for the new callbacks.  Extra points to anyone who
> sees how to avoid the extra code duplication.  :-)
>

Thanks for the series Richard. It looks good to me.

Besides reviewing individual commits, I have a more general question.
 From some discussions we had, it seems like that previously gdb stub 
was correctly updating all register values, and that it has been dropped 
at some point.

Was it for performance reasons, or an architectural change in QEMU?
Is gdb stub the right way to poke register values for plugins?

I don't know exactly why some registers are not updated correctly in 
this context, but it seems like we are trying to fix this afterward, 
instead of identifying root cause.

Sorry if my question is irrelevant, I'm trying to understand the full 
context here.

Thanks,
Pierrick

> 
> r~
> 
> 
> Richard Henderson (7):
>    tcg: Introduce INDEX_op_plugin_pc
>    accel/tcg: Set CPUState.plugin_ra before all plugin callbacks
>    accel/tcg: Return the TranslationBlock from cpu_unwind_state_data
>    plugins: Introduce TCGCPUOps callbacks for mid-tb register reads
>    target/i386: Split out gdb-internal.h
>    target/i386: Introduce cpu_compute_eflags_ccop
>    target/i386: Implement TCGCPUOps for plugin register reads
> 
>   include/exec/cpu-common.h     |  9 +++--
>   include/hw/core/cpu.h         |  1 +
>   include/hw/core/tcg-cpu-ops.h | 13 +++++++
>   include/tcg/tcg-op-common.h   |  1 +
>   include/tcg/tcg-opc.h         |  1 +
>   target/i386/cpu.h             |  2 +
>   target/i386/gdb-internal.h    | 65 +++++++++++++++++++++++++++++++
>   accel/tcg/plugin-gen.c        | 50 +++++++++++++++++++++---
>   accel/tcg/translate-all.c     |  9 +++--
>   plugins/api.c                 | 36 +++++++++++++++++-
>   target/i386/gdbstub.c         |  1 +
>   target/i386/helper.c          |  6 ++-
>   target/i386/tcg/cc_helper.c   | 10 +++++
>   target/i386/tcg/tcg-cpu.c     | 72 +++++++++++++++++++++++++++--------
>   tcg/tcg-op.c                  |  5 +++
>   tcg/tcg.c                     | 10 +++++
>   16 files changed, 258 insertions(+), 33 deletions(-)
>   create mode 100644 target/i386/gdb-internal.h
>