Re: [kvm-unit-tests PATCH v4 1/2] s390x: Add specification exception test

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Tue, 11 Jan 2022 17:39:00 +0100
Janis Schoetterl-Glausch <scgl@linux.ibm.com> wrote:

> Generate specification exceptions and check that they occur.
> 
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> ---
>  s390x/Makefile      |   1 +
>  s390x/spec_ex.c     | 154 ++++++++++++++++++++++++++++++++++++++++++++
>  s390x/unittests.cfg |   3 +
>  3 files changed, 158 insertions(+)
>  create mode 100644 s390x/spec_ex.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 1e567c1..5635c08 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -25,6 +25,7 @@ tests += $(TEST_DIR)/uv-host.elf
>  tests += $(TEST_DIR)/edat.elf
>  tests += $(TEST_DIR)/mvpg-sie.elf
>  tests += $(TEST_DIR)/spec_ex-sie.elf
> +tests += $(TEST_DIR)/spec_ex.elf
>  tests += $(TEST_DIR)/firq.elf
>  
>  tests_binary = $(patsubst %.elf,%.bin,$(tests))
> diff --git a/s390x/spec_ex.c b/s390x/spec_ex.c
> new file mode 100644
> index 0000000..a9f9f31
> --- /dev/null
> +++ b/s390x/spec_ex.c
> @@ -0,0 +1,154 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright IBM Corp. 2021
> + *
> + * Specification exception test.
> + * Tests that specification exceptions occur when expected.
> + *
> + * Can be extended by adding triggers to spec_ex_triggers, see comments below.
> + */
> +#include <stdlib.h>
> +#include <libcflat.h>
> +#include <asm/interrupt.h>
> +
> +static struct lowcore *lc = (struct lowcore *) 0;
> +
> +static bool invalid_psw_expected;
> +static struct psw expected_psw;
> +static struct psw invalid_psw;
> +static struct psw fixup_psw;
> +
> +/* The standard program exception handler cannot deal with invalid old PSWs,
> + * especially not invalid instruction addresses, as in that case one cannot
> + * find the instruction following the faulting one from the old PSW.
> + * The PSW to return to is set by load_psw.
> + */
> +static void fixup_invalid_psw(void)
> +{
> +	// signal occurrence of invalid psw fixup
> +	invalid_psw_expected = false;
> +	invalid_psw = lc->pgm_old_psw;
> +	lc->pgm_old_psw = fixup_psw;
> +}
> +
> +/* Load possibly invalid psw, but setup fixup_psw before,
> + * so that *fixup_invalid_psw() can bring us back onto the right track.

is the * just a typo?

> + * Also acts as compiler barrier, -> none required in expect/check_invalid_psw
> + */
> +static void load_psw(struct psw psw)
> +{
> +	uint64_t scratch;
> +
> +	fixup_psw.mask = extract_psw_mask();
> +	asm volatile ( "larl	%[scratch],nop%=\n"
> +		"	stg	%[scratch],%[addr]\n"
> +		"	lpswe	%[psw]\n"
> +		"nop%=:	nop\n"
> +		: [scratch] "=&r"(scratch),
> +		  [addr] "=&T"(fixup_psw.addr)
> +		: [psw] "Q"(psw)
> +		: "cc", "memory"
> +	);
> +}
> +
> +static void expect_invalid_psw(struct psw psw)
> +{
> +	expected_psw = psw;
> +	invalid_psw_expected = true;
> +}
> +
> +static int check_invalid_psw(void)
> +{
> +	// toggled to signal occurrence of invalid psw fixup

please use /* */ style of comments also for single line comments

> +	if (!invalid_psw_expected) {
> +		if (expected_psw.mask == invalid_psw.mask &&
> +		    expected_psw.addr == invalid_psw.addr)
> +			return 0;
> +		report_fail("Wrong invalid PSW");
> +	} else {
> +		report_fail("Expected exception due to invalid PSW");
> +	}
> +	return 1;
> +}
> +
> +static int psw_bit_12_is_1(void)
> +{
> +	struct psw invalid = { .mask = 0x0008000000000000, .addr = 0x00000000deadbeee};
> +
> +	expect_invalid_psw(invalid);
> +	load_psw(expected_psw);
> +	return check_invalid_psw();
> +}
> +
> +static int bad_alignment(void)
> +{
> +	uint32_t words[5] __attribute__((aligned(16)));
> +	uint32_t (*bad_aligned)[4] = (uint32_t (*)[4])&words[1];
> +
> +	asm volatile ("lpq %%r6,%[bad]"
> +		      : : [bad] "T"(*bad_aligned)
> +		      : "%r6", "%r7"
> +	);
> +	return 0;
> +}
> +
> +static int not_even(void)
> +{
> +	uint64_t quad[2] __attribute__((aligned(16))) = {0};
> +
> +	asm volatile (".insn	rxy,0xe3000000008f,%%r7,%[quad]" //lpq %%r7,%[quad]
> +		      : : [quad] "T"(quad)
> +		      : "%r7", "%r8"
> +	);
> +	return 0;
> +}
> +
> +/*
> + * Harness for specification exception testing.
> + * func only triggers exception, reporting is taken care of automatically.
> + */
> +struct spec_ex_trigger {
> +	const char *name;
> +	int (*func)(void);
> +	void (*fixup)(void);
> +};
> +
> +/* List of all tests to execute */
> +static const struct spec_ex_trigger spec_ex_triggers[] = {
> +	{ "psw_bit_12_is_1", &psw_bit_12_is_1, &fixup_invalid_psw },
> +	{ "bad_alignment", &bad_alignment, NULL },
> +	{ "not_even", &not_even, NULL },
> +	{ NULL, NULL, NULL },
> +};
> +
> +static void test_spec_ex(const struct spec_ex_trigger *trigger)
> +{
> +	uint16_t expected_pgm = PGM_INT_CODE_SPECIFICATION;
> +	uint16_t pgm;
> +	int rc;
> +
> +	expect_pgm_int();
> +	register_pgm_cleanup_func(trigger->fixup);
> +	rc = trigger->func();
> +	register_pgm_cleanup_func(NULL);
> +	if (rc)
> +		return;

why do you exit early in case of failure? (moreover, your are not even
reporting the failure)

> +	pgm = clear_pgm_int();
> +	report(pgm == expected_pgm, "Program interrupt: expected(%d) == received(%d)",
> +	       expected_pgm, pgm);
> +}
> +
> +int main(int argc, char **argv)
> +{
> +	unsigned int i;
> +
> +	report_prefix_push("specification exception");
> +	for (i = 0; spec_ex_triggers[i].name; i++) {
> +		report_prefix_push(spec_ex_triggers[i].name);
> +		test_spec_ex(&spec_ex_triggers[i]);
> +		report_prefix_pop();
> +	}
> +	report_prefix_pop();
> +
> +	return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 054560c..26510cf 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -113,6 +113,9 @@ file = mvpg-sie.elf
>  [spec_ex-sie]
>  file = spec_ex-sie.elf
>  
> +[spec_ex]
> +file = spec_ex.elf
> +
>  [firq-linear-cpu-ids]
>  file = firq.elf
>  timeout = 20