Re: [kvm-unit-tests PATCH v6 1/2] s390x: Add specification exception test

[Janosch Frank <frankja@linux.ibm.com>]

On 8/26/22 18:11, Janis Schoetterl-Glausch wrote:
> Generate specification exceptions and check that they occur.
> 
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>

Minor issues below, apart from that:
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>

> ---
>   s390x/Makefile           |   1 +
>   lib/s390x/asm/arch_def.h |   5 +
>   s390x/spec_ex.c          | 194 +++++++++++++++++++++++++++++++++++++++
>   s390x/unittests.cfg      |   3 +
>   4 files changed, 203 insertions(+)
>   create mode 100644 s390x/spec_ex.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index efd5e0c1..58b1bf54 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -27,6 +27,7 @@ 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 += $(TEST_DIR)/epsw.elf
>   tests += $(TEST_DIR)/adtl-status.elf
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index e7ae454b..b6e60fb0 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -41,6 +41,11 @@ struct psw {
>   	uint64_t	addr;
>   };
>   
> +struct short_psw {
> +	uint32_t	mask;
> +	uint32_t	addr;
> +};
> +
>   struct cpu {
>   	struct lowcore *lowcore;
>   	uint64_t *stack;
> diff --git a/s390x/spec_ex.c b/s390x/spec_ex.c
> new file mode 100644
> index 00000000..68469e4b
> --- /dev/null
> +++ b/s390x/spec_ex.c
> @@ -0,0 +1,194 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright IBM Corp. 2021, 2022
> + *
> + * 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 <bitops.h>
> +#include <asm/interrupt.h>
> +
> +/* toggled to signal occurrence of invalid psw fixup */
> +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(struct stack_frame_int *stack)
> +{
> +	/* signal occurrence of invalid psw fixup */
> +	invalid_psw_expected = false;

Hmmmm (TM), assert(invalid_psw_expected) ?

> +	invalid_psw = lowcore.pgm_old_psw;
> +	lowcore.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.
> + * Also acts as compiler barrier, -> none required in expect/check_invalid_psw
> + */
> +static void load_psw(struct psw psw)
> +{
> +	uint64_t scratch;
> +
> +	/*
> +	 * The fixup psw is current psw with the instruction address replaced by

is the current psw

> +	 * the address of the nop following the instruction loading the new psw. > +	 */
> +	fixup_psw.mask = extract_psw_mask();
> +	asm volatile ( "larl	%[scratch],0f\n"
> +		"	stg	%[scratch],%[fixup_addr]\n"
> +		"	lpswe	%[psw]\n"
> +		"0:	nop\n"
> +		: [scratch] "=&d" (scratch),
> +		  [fixup_addr] "=&T" (fixup_psw.addr)
> +		: [psw] "Q" (psw)
> +		: "cc", "memory"
> +	);
> +}
> +
> +static void load_short_psw(struct short_psw psw)
> +{
> +	uint64_t scratch;
> +
> +	fixup_psw.mask = extract_psw_mask();
> +	asm volatile ( "larl	%[scratch],0f\n"
> +		"	stg	%[scratch],%[fixup_addr]\n"
> +		"	lpsw	%[psw]\n"
> +		"0:	nop\n"
> +		: [scratch] "=&d" (scratch),
> +		  [fixup_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)
> +{

/* Since the fixup sets this to false we check for false here. */

> +	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;
> +}
> +