Re: [PATCH v2 2/2] tests/tcg/riscv64: add misa write test

On Mon, 2026-08-17 at 18:06 +0300, Vladimir Isaev wrote:
> Link:
> https://lore.kernel.org/r/[email protected]
> Suggested-by: Nicholas Piggin <[email protected]>
> Signed-off-by: Vladimir Isaev <[email protected]>

Reviewed-by: Alistair Francis <[email protected]>

Alistair

> ---
>  tests/tcg/riscv64/Makefile.softmmu-target |  4 ++
>  tests/tcg/riscv64/test-misa-w.S           | 88
> +++++++++++++++++++++++
>  2 files changed, 92 insertions(+)
>  create mode 100644 tests/tcg/riscv64/test-misa-w.S
> 
> diff --git a/tests/tcg/riscv64/Makefile.softmmu-target
> b/tests/tcg/riscv64/Makefile.softmmu-target
> index 82be8a2c91..2c7f00976c 100644
> --- a/tests/tcg/riscv64/Makefile.softmmu-target
> +++ b/tests/tcg/riscv64/Makefile.softmmu-target
> @@ -41,5 +41,9 @@ comma:= ,
>  run-test-crc32: test-crc32
>  	$(call run-test, $<, $(QEMU) -cpu rv64$(comma)xlrbr=true
> $(QEMU_OPTS)$<)
>  
> +EXTRA_RUNS += run-test-misa-w
> +run-test-misa-w: test-misa-w
> +	$(call run-test, $<, $(QEMU) -cpu rv64$(comma)x-misa-
> w=true$(comma)c=true$(comma)v=true $(QEMU_OPTS)$<)
> +
>  # We don't currently support the multiarch system tests
>  undefine MULTIARCH_TESTS
> diff --git a/tests/tcg/riscv64/test-misa-w.S
> b/tests/tcg/riscv64/test-misa-w.S
> new file mode 100644
> index 0000000000..7f1eb30023
> --- /dev/null
> +++ b/tests/tcg/riscv64/test-misa-w.S
> @@ -0,0 +1,88 @@
> +/*
> + * Test for MISA changing C and related IALIGN alignment cases
> + *
> + * This test verifies that the "C" extension can be cleared and set
> in MISA,
> + * that a branch to 2-byte aligned instructions can be executed when
> "C" is
> + * enabled, and that a write to MISA which would increase IALIGN and
> cause
> + * the next instruction to be unaligned is ignored.
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#define RVC (1 << ('C'-'A'))
> +#define RVV (1 << ('V'-'A'))
> +
> +.option norvc
> +	.text
> +	.global _start
> +_start:
> +	lla	t0, trap
> +	csrw	mtvec, t0
> +
> +	csrr	t0, misa
> +	li	t1, RVC
> +	not	t1, t1
> +	and	t0, t0, t1
> +	csrw	misa, t0
> +	csrr	t1, misa
> +	li	a0, 2 # fail code
> +	bne	t0, t1, _exit # Could not clear RVC in MISA
> +
> +	li	t1, RVC
> +	or	t0, t0, t1
> +	csrw	misa, t0
> +	csrr	t1, misa
> +	li	a0, 3 # fail code
> +	bne	t0, t1, _exit # Could not set RVC in MISA
> +
> +	j	unalign
> +. = . + 2
> +unalign:
> +
> +	li	t1, RVC
> +	not	t1, t1
> +	and	t0, t0, t1
> +	csrw	misa, t0
> +	csrr	t1, misa
> +	li	a0, 4 # fail code
> +	beq	t0, t1, _exit # Was able to clear RVC in MISA
> +
> +	li	t0, (RVC|RVV)
> +	not	t0, t0
> +	and	t0, t0, t1
> +	csrw	misa, t0
> +	csrr	t0, misa
> +	li	a0, 5 # fail code
> +	bne	t0, t1, _exit # MISA write was not ignored (RVV was
> cleared)
> +
> +	j	realign
> +. = . + 2
> +realign:
> +
> +	# Success!
> +	li	a0, 0
> +	j	_exit
> +
> +trap:
> +	# Any trap is a fail code 1
> +	li	a0, 1
> +
> +# Exit code in a0
> +_exit:
> +	lla	a1, semiargs
> +	li	t0, 0x20026	# ADP_Stopped_ApplicationExit
> +	sd	t0, 0(a1)
> +	sd	a0, 8(a1)
> +	li	a0, 0x20	# TARGET_SYS_EXIT_EXTENDED
> +
> +	# Semihosting call sequence
> +	.balign	16
> +	slli	zero, zero, 0x1f
> +	ebreak
> +	srai	zero, zero, 0x7
> +	j	.
> +
> +	.data
> +	.balign	16
> +semiargs:
> +	.space	16