kselftest/arm64: Cover ZT in the FP stress test

Hook up the newly added zt-test program in the FPSIMD stress tests, start
a copy per CPU when SME2 is supported.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221208-arm64-sme2-v4-15-f2fa0aef982f@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Skip non-power of 2 SVE vector lengths in fp-stress

As documented in issue C215 in the known issues list for DDI0487I.a [1] Arm
will be making a retroactive change to SVE to remove the possibility of
selecting non power of two vector lengths. This has no impact on existing
physical implementations but most virtual implementations have implemented
the full range of permissible vector lengths. Given how demanding fp-stress
is for these implementations update to only attempt to enumerate the power
of two vector lengths, reducing the load created on existing virtual
implementations and only exercising the functionality that will be seen in
physical implementations.

[1] https://developer.arm.com/documentation/102105/ia-00/

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221220-arm64-fp-stress-pow2-v1-1-d0ce756b57af@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Allow epoll_wait() to return more than one result

When everything is starting up we are likely to have a lot of child
processes producing output at once. This means that we can reduce
overhead a bit by allowing epoll_wait() to return more than one
descriptor at once, it cuts down on the number of system calls we need
to do which on virtual platforms where the syscall overhead is a bit
more noticable and we're likely to have a lot more children active can
make a small but noticable difference.

On physical platforms the relatively small number of processes being run
and vastly improved speeds push the effects of this change into the
noise.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221129215926.442895-4-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Don't drain output while spawning children

Now we hold execution of the stress test programs until all children are
started there is no need to drain output while that is happening.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221129215926.442895-3-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Hold fp-stress children until they're all spawned

At present fp-stress has a bit of a thundering herd problem since the
children it spawns start running immediately, meaning that they can start
starving the parent process of CPU before it has even started all the
children. This is much more severe on virtual platforms since they tend to
support far more SVE and SME vector lengths, be slower in general and for
some have issues with performance when simulating multiple CPUs.

We can mitigate this problem by having all the child processes block before
starting the test program, meaning that we at least have all the child
processes started before we start heavily using CPU. We still have the same
load issues while waiting for the actual stress test programs to start up
and produce output but they're at least all ready to go before that kicks
in, resulting in substantial reductions in overall runtime on some of the
severely affected systems. One test was showing about 20% improvement.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221129215926.442895-2-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Set test names prior to starting children

Since we now flush output immediately on starting children we should ensure
that the child name is set beforehand so that any output that does get
flushed from the newly created child has the name of the child attached.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221124120722.150988-1-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Provide progress messages when signalling children

Especially when the test is configured to run for a longer time it can be
reassuring to users to see that the supervising program is running OK so
provide a message every second when the output timer expires.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221017144553.773176-3-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Check that all children are producing output in fp-stress

Currently we don't have an explicit check that when it's been a second
since we have seen output produced from the test programs starting up that
means all of them are running and we should start both sending signals and
timing out. This is not reliable, especially on very heavily loaded systems
where the test programs might take longer than a second to run.

We do skip sending signals to children that have not produced output yet
so we won't cause them to exit unexpectedly by sending a signal but this
can create confusion when interpreting output, for example appearing to
show the tests running for less time than expected or appearing to show
missed signal deliveries. Avoid issues by explicitly checking that we have
seen output from all the child processes before we start sending signals
or counting test run time.

This is especially likely on virtual platforms with large numbers of vector
lengths supported since the platforms are slow and there will be a lot of
tasks per CPU.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221017144553.773176-2-broonie@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

kselftest/arm64: Handle EINTR while reading data from children

Currently we treat any error when reading from the child as a failure and
don't read any more output from that child as a result. This ignores the
fact that it is valid for read() to return EINTR as the error code if there
is a signal pending so we could stop handling the output of children,
especially during exit when we will get some SIGCHLD signals delivered to
us. Fix this by pulling the read handling out into a separate function
which returns a flag if reads should be continued and wrapping it in a
loop.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220921181345.618085-4-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Flag fp-stress as exiting when we begin finishing up

Once we have started exiting the termination handler will have the same
effect as what we're already running so set the termination flag at that
point.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220921181345.618085-3-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Don't repeat termination handler for fp-stress

When fp-stress gets a termination signal it sets a flag telling itself to
exit and sends a termination signal to all the children. If the flag is set
then don't bother repeating this process, it isn't going to accomplish
anything other than consume CPU time which can be an issue when running in
emulation.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220921181345.618085-2-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: Fix spelling misakes of signal names

There are a couple of spelling mistakes of signame names. Fix them.

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Link: https://lore.kernel.org/r/20220907170902.687340-1-colin.i.king@gmail.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

kselftest/arm64: kselftest harness for FP stress tests

Currently the stress test programs for floating point context switching are
run by hand, there are extremely simplistic harnesses which run some copies
of each test individually but they are not integrated into kselftest and
with SVE and SME they only run with whatever vector length the process has
by default. This is hassle when running the tests and means that they're
not being run at all by CI systems picking up kselftest.

In order to improve our coverage and provide a more convenient interface
provide a harness program which starts enough stress test programs up to
cause context switching and runs them for a set period. If only FPSIMD is
available in the system we start two copies of the FPSIMD stress test per
CPU, otherwise we start one copy of the FPSIMD and then start the SVE,
streaming SVE and ZA tests once per CPU for each available VL they have
to run on. We then run for a set period monitoring for any errors
reported by the test programs before cleanly terminating them.

In order to provide additional coverage of signal handling and some extra
noise in the scheduling we send a SIGUSR2 to the stress tests once a
second, the tests will count the number of signals they get.

Since kselftest is generally expected to run quickly we by default only run
for ten seconds. This is enough to show if there is anything cripplingly
wrong but not exactly a thorough soak test, for interactive and more
focused use a command line option -t N is provided which overrides the
length of time to run for (specified in seconds) and if 0 is specified then
there is no timeout and the test must be manually terminated. The timeout
is counted in seconds with no output, this is done to account for the
potentially slow startup time for the test programs on virtual platforms
which tend to struggle during startup as they are both slow and tend to
support a wide range of vector lengths.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20220829154452.824870-5-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>