selftests: arm64: Add build and documentation for FP tests

ARCH ?= $(shell uname -m 2>/dev/null || echo not)

ifneq (,$(filter $(ARCH),aarch64 arm64))

ARM64_SUBTARGETS ?= tags signal pauth

ARM64_SUBTARGETS ?= tags signal pauth fp

else

ARM64_SUBTARGETS :=

endif

fpsimd-test

sve-probe-vls

sve-ptrace

sve-test

vlset

# SPDX-License-Identifier: GPL-2.0

CFLAGS += -I../../../../../usr/include/

TEST_GEN_PROGS := sve-ptrace sve-probe-vls

TEST_PROGS_EXTENDED := fpsimd-test fpsimd-stress sve-test sve-stress vlset

all: $(TEST_GEN_PROGS) $(TEST_PROGS_EXTENDED)

fpsimd-test: fpsimd-test.o

	$(CC) -nostdlib $^ -o $@

sve-ptrace: sve-ptrace.o sve-ptrace-asm.o

sve-probe-vls: sve-probe-vls.o

sve-test: sve-test.o

	$(CC) -nostdlib $^ -o $@

vlset: vlset.o

include ../../lib.mk

This directory contains a mix of tests integrated with kselftest and

standalone stress tests.

kselftest tests

===============

sve-probe-vls - Checks the SVE vector length enumeration interface

sve-ptrace - Checks the SVE ptrace interface

Running the non-kselftest tests

===============================

sve-stress performs an SVE context switch stress test, as described

below.

(The fpsimd-stress test works the same way; just substitute "fpsimd" for

"sve" in the following commands.)

The test runs until killed by the user.

If no context switch error was detected, you will see output such as

the following:

$ ./sve-stress

(wait for some time)

^C

Vector length:        512 bits

PID:    1573

Terminated by signal 15, no error, iterations=9467, signals=1014

Vector length:  512 bits

PID:    1575

Terminated by signal 15, no error, iterations=9448, signals=1028

Vector length:  512 bits

PID:    1577

Terminated by signal 15, no error, iterations=9436, signals=1039

Vector length:  512 bits

PID:    1579

Terminated by signal 15, no error, iterations=9421, signals=1039

Vector length:  512 bits

PID:    1581

Terminated by signal 15, no error, iterations=9403, signals=1039

Vector length:  512 bits

PID:    1583

Terminated by signal 15, no error, iterations=9385, signals=1036

Vector length:  512 bits

PID:    1585

Terminated by signal 15, no error, iterations=9376, signals=1039

Vector length:  512 bits

PID:    1587

Terminated by signal 15, no error, iterations=9361, signals=1039

Vector length:  512 bits

PID:    1589

Terminated by signal 15, no error, iterations=9350, signals=1039

If an error was detected, details of the mismatch will be printed

instead of "no error".

Ideally, the test should be allowed to run for many minutes or hours

to maximise test coverage.

KVM stress testing

==================

To try to reproduce the bugs that we have been observing, sve-stress

should be run in parallel in two KVM guests, while simultaneously

running on the host.

1) Start 2 guests, using the following command for each:

$ lkvm run --console=virtio -pconsole=hvc0 --sve Image

(Depending on the hardware GIC implementation, you may also need

--irqchip=gicv3.  New kvmtool defaults to that if appropriate, but I

can't remember whether my branch is new enough for that.  Try without

the option first.)

Kvmtool occupies the terminal until you kill it (Ctrl+A x),

or until the guest terminates.  It is therefore recommended to run

each instance in separate terminal (use screen or ssh etc.)  This

allows multiple guests to be run in parallel while running other

commands on the host.

Within the guest, the host filesystem is accessible, mounted on /host.

2) Run the sve-stress on *each* guest with the Vector-Length set to 32:

guest$ ./vlset --inherit 32 ./sve-stress

3) Run the sve-stress on the host with the maximum Vector-Length:

host$ ./vlset --inherit --max ./sve-stress

Again, the test should be allowed to run for many minutes or hours to

maximise test coverage.

If no error is detected, you will see output from each sve-stress

instance similar to that illustrated above; otherwise details of the

observed mismatches will be printed.