Commit Graph

9 Commits

Author SHA1 Message Date
Alex Bennée
c81950a2f1 plugins: new lockstep plugin for debugging TCG changes
When we make changes to the TCG we sometimes cause regressions that
are deep into the execution cycle of the guest. Debugging this often
requires comparing large volumes of trace information to figure out
where behaviour has diverged.

The lockstep plugin utilises a shared socket so two QEMU's running
with the plugin will write their current execution position and wait
to receive the position of their partner process. When execution
diverges the plugins output where they were and the previous few
blocks before unloading themselves and letting execution continue.

Originally I planned for this to be most useful with -icount but it
turns out you can get divergence pretty quickly due to asynchronous
qemu_cpu_kick_rr_cpus() events causing one side to eventually run into
a short block a few cycles before the other side. For this reason I've
added a bit of tracking and I think the divergence reporting could be
finessed to report only if we really start to diverge in execution.

An example run would be:

  qemu-system-sparc -monitor none -parallel none -net none \
    -M SS-20 -m 256 -kernel day11/zImage.elf \
    -plugin ./tests/plugin/liblockstep.so,arg=lockstep-sparc.sock \
    -d plugin,nochain

with an identical command in another window in the same working
directory.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
Tested-by: Robert Foley <robert.foley@linaro.org>
Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20200610155509.12850-3-alex.bennee@linaro.org>
2020-06-16 14:49:05 +01:00
Alex Bennée
4e62bfa9ee tests/plugin: correctly honour io_count
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20200605154929.26910-4-alex.bennee@linaro.org>
2020-06-08 16:59:31 +01:00
Alex Bennée
ec11c4a8ec tests/plugins: make howvec clean-up after itself.
TCG plugins are responsible for their own memory usage and although
the plugin_exit is tied to the end of execution in this case it is
still poor practice. Ensure we delete the hash table and related data
when we are done to be a good plugin citizen.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

Message-Id: <20200225124710.14152-16-alex.bennee@linaro.org>
2020-02-25 20:20:23 +00:00
Chen Qun
4133686110 tests/plugin: prevent uninitialized warning
According to the glibc function requirements, we need initialise
 the variable. Otherwise there will be compilation warnings:

glib-autocleanups.h:28:3: warning: ‘out’ may be
used uninitialized in this function [-Wmaybe-uninitialized]
   g_free (*pp);
   ^~~~~~~~~~~~

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20200206093238.203984-1-kuhn.chenqun@huawei.com>
[AJB: uses Thomas's single line allocation]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200225124710.14152-13-alex.bennee@linaro.org>
2020-02-25 20:20:23 +00:00
Alex Bennée
3fb356cc86 tcg plugins: expose an API version concept
This is a very simple versioning API which allows the plugin
infrastructure to check the API a plugin was built against. We also
expose a min/cur API version to the plugin via the info block in case
it wants to avoid using old deprecated APIs in the future.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Robert Foley <robert.foley@linaro.org>
2019-11-12 14:32:55 +00:00
Alex Bennée
12268df393 tests/plugin: add hotpages to analyse memory access patterns
This plugin gives a summary of access patterns grouped by "pages" and
showing read/write patterns by vCPUS.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2019-10-28 15:12:38 +00:00
Alex Bennée
f79e8fa3b7 tests/plugin: add instruction execution breakdown
This gives a break down of instruction classes and individual
instruction types.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2019-10-28 15:12:38 +00:00
Alex Bennée
a208ba09bd tests/plugin: add a hotblocks plugin
This is a simple plugin to track which translation blocks are call
most often. As we don't have a view of the internals of TCG we can
only work by the address of the start of the block so we also need to
tracks how often the address is translated.

As there will be multiple blocks starting at the same address. We can
try and work around this by futzing the value to feed to the hash with
the insn count.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2019-10-28 15:12:38 +00:00
Emilio G. Cota
671f760b93 tests/plugin: add sample plugins
Pass arguments with -plugin=libfoo.so,arg=bar,arg=baz

Signed-off-by: Emilio G. Cota <cota@braap.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
2019-10-28 15:12:38 +00:00