Re: [Qemu-devel] [PATCH v3 00/50] tcg plugin support

[Alex Bennée]

Aleksandar Markovic <address@hidden> writes:

> On Fri, Jun 14, 2019 at 7:22 PM Alex Bennée <address@hidden> wrote:
>>
>> Hi,
>>
>> This is v3 of the proposed plugins API for QEMU. As Emilio is busy
>> having finished his time at Columbia I have volunteered to take the
>> patch series forward. Emilio's RFC v2 was posted last year:
>>
>>   Subject: [RFC v2 00/38] Plugin support
>>   Date: Sun,  9 Dec 2018 14:37:11 -0500
>>   Message-Id: <address@hidden>
>>
>> The idea is to present a plugin interface that allows for interesting
>> experiments to be written while not exposing the internal details of
>> how the TCG works to the wider world.
>>
>> Changes from last year
>>
>>   - re-basing and fixing up conflicts
>>   - moved to plugins/ and split files up (core/api/loader)
>>   - added a design document (docs/devel/plugins.rst)
>>   - replaced auto-growing structures with glib GArray and friends
>>   - expanded API to include access to disassembly
>>   - wrote some more example plugins
>>   - dropped the RFC tag ;-)
>>
>> There are a few things left to sort out. Currently the haddr
>> calculation relies on the softmmu TLB code for each architecture to
>> dump it in a cpu_env location. Currently this is only done on x86 and
>> we would require some tweaking to each backend. I think it would
>> probably be better to just have a wrapper helper which could do the
>> lookup of the (hot) TLB in C to calculate the address before calling
>> the helpers.
>>
>
> Great to see this series!
>
> Is there any particular conceptual reason why not all targets are included
> (i.e. mips, s390, etc.)? Or it was just, let's say, lack of your time 
> resources
> to complete everything?

There are two things.

Firstly this only supports guests that have been converted to the common
translator_loop code. This is to avoid having hooks in all the various
guest front-ends. I think we are slowly moving to having the common
translator_loop as mandatory and once that's done the guest gets plugins
"for free".

The only other change needed for each guest is to use the common
translator_ld function to read instructions. This again avoids us having
to have too many tendrils into the guests. arm's handling of endian
switching being the exception in this case.

AFAICT both mips and s390 are using the common loop stuff so it should
just be a case of adding the relevant translator_ld calls. The only
minor wrinkle would be if they do anything fancy like SH4's gUSA
sequence.

>
> Yours,
> Aleksandar
>
>> I also ended up adding a bunch of miscellaneous fixes at the end while
>> I was re-spinning. If they get some review I'll try and get the
>> non-controversial stuff up-streamed first.
>>
>> The area that needs the most review is the single pass TCG op
>> insertion code. When plugins are enabled each instruction gets dummy
>> ops inserted and then at the end we swap those out for the actual
>> calls or remove them from the stream. Hopefully this is not too much
>> of an abuse of TCG mechanisms.
>>
>> I'm aiming to get this in for 4.1 but I guess that will depend on how
>> the review and iteration goes.
>>
>> Alex Bennée (12):
>>   docs/devel: add plugins.rst design document
>>   configure: add --enable-plugins (MOVE TO END)
>>   plugin: add implementation of the api
>>   tests/tcg: enable plugin testing
>>   tests/plugin: add a hotblocks plugin
>>   plugin: add qemu_plugin_insn_disas helper
>>   tests/plugin: add instruction execution breakdown
>>   tests/plugin: add hotpages plugin to breakdown memory access patterns
>>   accel/stubs: reduce headers from tcg-stub
>>   include/exec: wrap cpu_ldst.h in CONFIG_TCG
>>   include/exec/cpu-defs.h: fix typo
>>   TODO: API changes to make?
>>
>> Emilio G. Cota (36):
>>   trace: expand mem_info:size_shift to 3 bits
>>   tcg/README: fix typo s/afterwise/afterwards/
>>   cpu: introduce cpu_in_exclusive_work_context()
>>   translate-all: use cpu_in_exclusive_work_context() in tb_flush
>>   plugin: add user-facing API
>>   plugin: add core code
>>   queue: add QTAILQ_REMOVE_SEVERAL
>>   cputlb: document get_page_addr_code
>>   cputlb: introduce get_page_addr_code_hostp
>>   plugin-gen: add module for TCG-related code
>>   tcg: add tcg_gen_st_ptr
>>   tcg: add MO_HADDR to TCGMemOp
>>   atomic_template: fix indentation in GEN_ATOMIC_HELPER
>>   atomic_template: add inline trace/plugin helpers
>>   cpu_ldst_useronly_template: remove redundant #ifndef CODE_ACCESS
>>   tcg: let plugins instrument memory accesses
>>   translate-all: notify plugin code of tb_flush
>>   *-user: notify plugin of exit
>>   *-user: plugin syscalls
>>   cpu: hook plugin vcpu events
>>   plugin-gen: add plugin_insn_append
>>   translator: add translator_ld{ub,sw,uw,l,q}
>>   target/arm: call qemu_plugin_insn_append
>>   target/ppc: fetch code with translator_ld
>>   target/sh4: fetch code with translator_ld
>>   target/i386: fetch code with translator_ld
>>   target/hppa: fetch code with translator_ld
>>   target/m68k: fetch code with translator_ld
>>   target/alpha: fetch code with translator_ld
>>   target/riscv: fetch code with translator_ld
>>   target/sparc: fetch code with translator_ld
>>   target/xtensa: fetch code with translator_ld
>>   target/openrisc: fetch code with translator_ld
>>   translator: inject instrumentation from plugins
>>   plugin: add API symbols to qemu-plugins.symbols
>>   tests/plugin: add sample plugins
>>
>> Lluís Vilanova (2):
>>   vl: support -plugin option
>>   linux-user: support -plugin option
>>
>>  Makefile                                  |   11 +-
>>  Makefile.target                           |    2 +
>>  accel/stubs/tcg-stub.c                    |    3 -
>>  accel/tcg/Makefile.objs                   |    1 +
>>  accel/tcg/atomic_template.h               |  117 ++-
>>  accel/tcg/cpu-exec.c                      |    3 +
>>  accel/tcg/cputlb.c                        |   56 +-
>>  accel/tcg/plugin-gen.c                    | 1079 +++++++++++++++++++++
>>  accel/tcg/plugin-helpers.h                |    6 +
>>  accel/tcg/translate-all.c                 |   15 +-
>>  accel/tcg/translator.c                    |   16 +
>>  bsd-user/syscall.c                        |   12 +
>>  configure                                 |   86 +-
>>  cpus-common.c                             |    2 +
>>  cpus.c                                    |   10 +
>>  disas.c                                   |  103 ++
>>  docs/devel/index.rst                      |    1 +
>>  docs/devel/plugins.rst                    |   99 ++
>>  exec.c                                    |    2 +
>>  include/disas/disas.h                     |    2 +
>>  include/exec/cpu-defs.h                   |   11 +-
>>  include/exec/cpu_ldst.h                   |    9 +
>>  include/exec/cpu_ldst_template.h          |   40 +-
>>  include/exec/cpu_ldst_useronly_template.h |   36 +-
>>  include/exec/exec-all.h                   |   64 +-
>>  include/exec/helper-gen.h                 |    1 +
>>  include/exec/helper-proto.h               |    1 +
>>  include/exec/helper-tcg.h                 |    1 +
>>  include/exec/plugin-gen.h                 |   71 ++
>>  include/exec/translator.h                 |   30 +-
>>  include/qemu/plugin.h                     |  261 +++++
>>  include/qemu/qemu-plugin.h                |  349 +++++++
>>  include/qemu/queue.h                      |   10 +
>>  include/qom/cpu.h                         |   19 +
>>  linux-user/exit.c                         |    1 +
>>  linux-user/main.c                         |   18 +
>>  linux-user/syscall.c                      |    3 +
>>  plugins/.gitignore                        |    2 +
>>  plugins/Makefile.objs                     |   21 +
>>  plugins/api.c                             |  274 ++++++
>>  plugins/core.c                            |  524 ++++++++++
>>  plugins/loader.c                          |  353 +++++++
>>  plugins/plugin.h                          |   95 ++
>>  plugins/qemu-plugins.symbols              |   36 +
>>  qemu-options.hx                           |   17 +
>>  qom/cpu.c                                 |    2 +
>>  target/alpha/translate.c                  |    2 +-
>>  target/arm/translate-a64.c                |    2 +
>>  target/arm/translate.c                    |    8 +-
>>  target/hppa/translate.c                   |    2 +-
>>  target/i386/translate.c                   |   10 +-
>>  target/m68k/translate.c                   |    2 +-
>>  target/openrisc/translate.c               |    2 +-
>>  target/ppc/translate.c                    |    8 +-
>>  target/riscv/translate.c                  |    2 +-
>>  target/sh4/translate.c                    |    4 +-
>>  target/sparc/translate.c                  |    2 +-
>>  target/xtensa/translate.c                 |    4 +-
>>  tcg/README                                |    2 +-
>>  tcg/i386/tcg-target.inc.c                 |    8 +
>>  tcg/tcg-op.c                              |   40 +-
>>  tcg/tcg-op.h                              |   16 +
>>  tcg/tcg-opc.h                             |    3 +
>>  tcg/tcg.c                                 |   22 +
>>  tcg/tcg.h                                 |   28 +
>>  tests/Makefile.include                    |   10 +-
>>  tests/plugin/Makefile                     |   31 +
>>  tests/plugin/bb.c                         |   66 ++
>>  tests/plugin/empty.c                      |   30 +
>>  tests/plugin/hotblocks.c                  |  145 +++
>>  tests/plugin/hotpages.c                   |  152 +++
>>  tests/plugin/howvec.c                     |  297 ++++++
>>  tests/plugin/insn.c                       |   63 ++
>>  tests/plugin/mem.c                        |   93 ++
>>  tests/tcg/Makefile                        |   34 +
>>  tests/tcg/arm/Makefile.softmmu-target     |    1 +
>>  trace-events                              |    2 +-
>>  vl.c                                      |   11 +
>>  78 files changed, 4855 insertions(+), 122 deletions(-)
>>  create mode 100644 accel/tcg/plugin-gen.c
>>  create mode 100644 accel/tcg/plugin-helpers.h
>>  create mode 100644 docs/devel/plugins.rst
>>  create mode 100644 include/exec/plugin-gen.h
>>  create mode 100644 include/qemu/plugin.h
>>  create mode 100644 include/qemu/qemu-plugin.h
>>  create mode 100644 plugins/.gitignore
>>  create mode 100644 plugins/Makefile.objs
>>  create mode 100644 plugins/api.c
>>  create mode 100644 plugins/core.c
>>  create mode 100644 plugins/loader.c
>>  create mode 100644 plugins/plugin.h
>>  create mode 100644 plugins/qemu-plugins.symbols
>>  create mode 100644 tests/plugin/Makefile
>>  create mode 100644 tests/plugin/bb.c
>>  create mode 100644 tests/plugin/empty.c
>>  create mode 100644 tests/plugin/hotblocks.c
>>  create mode 100644 tests/plugin/hotpages.c
>>  create mode 100644 tests/plugin/howvec.c
>>  create mode 100644 tests/plugin/insn.c
>>  create mode 100644 tests/plugin/mem.c
>>
>> --
>> 2.20.1
>>
>>


--
Alex Bennée