On Wed, Sep 01, 2021 at 09:14:08PM +0000, Raghavendra Rao Ananta wrote:
> Add a simpler version of spinlock support for ARM64 for
> the guests to use.
>
> The implementation is loosely based on the spinlock
> implementation in kvm-unit-tests.
>
> Signed-off-by: Raghavendra Rao Ananta <rananta@xxxxxxxxxx>
> ---
> tools/testing/selftests/kvm/Makefile | 2 +-
> .../selftests/kvm/include/aarch64/spinlock.h | 13 +++++++++
> .../selftests/kvm/lib/aarch64/spinlock.c | 27 +++++++++++++++++++
> 3 files changed, 41 insertions(+), 1 deletion(-)
> create mode 100644 tools/testing/selftests/kvm/include/aarch64/spinlock.h
> create mode 100644 tools/testing/selftests/kvm/lib/aarch64/spinlock.c
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 5d05801ab816..61f0d376af99 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -35,7 +35,7 @@ endif
>
> LIBKVM = lib/assert.c lib/elf.c lib/io.c lib/kvm_util.c lib/rbtree.c lib/sparsebit.c lib/test_util.c lib/guest_modes.c lib/perf_test_util.c
> LIBKVM_x86_64 = lib/x86_64/apic.c lib/x86_64/processor.c lib/x86_64/vmx.c lib/x86_64/svm.c lib/x86_64/ucall.c lib/x86_64/handlers.S
> -LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c lib/aarch64/handlers.S
> +LIBKVM_aarch64 = lib/aarch64/processor.c lib/aarch64/ucall.c lib/aarch64/handlers.S lib/aarch64/spinlock.c
> LIBKVM_s390x = lib/s390x/processor.c lib/s390x/ucall.c lib/s390x/diag318_test_handler.c
>
> TEST_GEN_PROGS_x86_64 = x86_64/cr4_cpuid_sync_test
> diff --git a/tools/testing/selftests/kvm/include/aarch64/spinlock.h b/tools/testing/selftests/kvm/include/aarch64/spinlock.h
> new file mode 100644
> index 000000000000..cf0984106d14
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/include/aarch64/spinlock.h
> @@ -0,0 +1,13 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef SELFTEST_KVM_ARM64_SPINLOCK_H
> +#define SELFTEST_KVM_ARM64_SPINLOCK_H
> +
> +struct spinlock {
> + int v;
> +};
> +
> +extern void spin_lock(struct spinlock *lock);
> +extern void spin_unlock(struct spinlock *lock);
> +
> +#endif /* SELFTEST_KVM_ARM64_SPINLOCK_H */
> diff --git a/tools/testing/selftests/kvm/lib/aarch64/spinlock.c b/tools/testing/selftests/kvm/lib/aarch64/spinlock.c
> new file mode 100644
> index 000000000000..6d66a3dac237
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/lib/aarch64/spinlock.c
> @@ -0,0 +1,27 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * ARM64 Spinlock support
> + */
> +#include <stdint.h>
> +
> +#include "spinlock.h"
> +
> +void spin_lock(struct spinlock *lock)
> +{
> + uint32_t val, res;
> +
> + asm volatile(
> + "1: ldaxr %w0, [%2]\n"
> + " cbnz %w0, 1b\n"
> + " mov %w0, #1\n"
> + " stxr %w1, %w0, [%2]\n"
> + " cbnz %w1, 1b\n"
> + : "=&r" (val), "=&r" (res)
> + : "r" (&lock->v)
> + : "memory");
> +}
> +
> +void spin_unlock(struct spinlock *lock)
> +{
> + asm volatile("stlr wzr, [%0]\n" : : "r" (&lock->v) : "memory");
> +}
> --
Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
It makes sense that the explicit barriers in kvm-unit-tests weren't also
inherited, because we already have the implicit barriers with these ld/st
instruction variants. (I suppose we could improve the kvm-unit-tests
implementation at some point.)
Thanks,
drew
