Re: [kvm-unit-tests PATCH] s390x: Add specification exception test

Thomas Huth
2021-07-21T13:27:00Z

On 06/07/2021 13.54, Janis Schoetterl-Glausch wrote:
> Generate specification exceptions and check that they occur.
> Also generate specification exceptions during a transaction,
> which results in another interruption code.
> With the iterations argument one can check if specification
> exception interpretation occurs, e.g. by using a high value and
> checking that the debugfs counters are substantially lower.
> The argument is also useful for estimating the performance benefit
> of interpretation.
>
> Signed-off-by: Janis Schoetterl-Glausch <scgl@linux.ibm.com>
> ---
> s390x/Makefile | 1 +
> lib/s390x/asm/arch_def.h | 1 +
> s390x/spec_ex.c | 344 +++++++++++++++++++++++++++++++++++++++
> s390x/unittests.cfg | 3 +
> 4 files changed, 349 insertions(+)
> create mode 100644 s390x/spec_ex.c
>
> diff --git a/s390x/Makefile b/s390x/Makefile
> index 8820e99..be100d3 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -23,6 +23,7 @@ tests += $(TEST_DIR)/sie.elf
> tests += $(TEST_DIR)/mvpg.elf
> tests += $(TEST_DIR)/uv-host.elf
> tests += $(TEST_DIR)/edat.elf
> +tests += $(TEST_DIR)/spec_ex.elf
>
> tests_binary = $(patsubst %.elf,%.bin,$(tests))
> ifneq ($(HOST_KEY_DOCUMENT),)
> diff --git a/lib/s390x/asm/arch_def.h b/lib/s390x/asm/arch_def.h
> index 15cf7d4..7cb0b92 100644
> --- a/lib/s390x/asm/arch_def.h
> +++ b/lib/s390x/asm/arch_def.h
> @@ -229,6 +229,7 @@ static inline uint64_t stctg(int cr)
> return value;
> }
>
> +#define CTL0_TRANSACT_EX_CTL (63 - 8)
> #define CTL0_LOW_ADDR_PROT (63 - 35)
> #define CTL0_EDAT (63 - 40)
> #define CTL0_IEP (63 - 43)
> diff --git a/s390x/spec_ex.c b/s390x/spec_ex.c
> new file mode 100644
> index 0000000..2e05bfb
> --- /dev/null
> +++ b/s390x/spec_ex.c
> @@ -0,0 +1,344 @@

Please add a short comment header at the top of the file with some
information on what it is all about, and license information (e.g. a
SPDX-License-Identifier)

> +#include <stdlib.h>
> +#include <htmintrin.h>
> +#include <libcflat.h>
> +#include <asm/barrier.h>
> +#include <asm/interrupt.h>
> +#include <asm/facility.h>
> +
> +struct lowcore *lc = (struct lowcore *) 0;
> +
> +static bool expect_early;
> +static struct psw expected_early_pgm_psw;
> +static struct psw fixup_early_pgm_psw;
> +
> +static void fixup_early_pgm_ex(void)

Could you please add a comment in front of this function with a description
why this is required / good for?

> +{
> + if (expect_early) {
> + report(expected_early_pgm_psw.mask == lc->pgm_old_psw.mask
> + && expected_early_pgm_psw.addr == lc->pgm_old_psw.addr,
> + "Early program new PSW as expected");
> + expect_early = false;
> + }
> + lc->pgm_old_psw = fixup_early_pgm_psw;
> +}
> +
> +static void lpsw(uint64_t psw)
> +{
> + uint32_t *high, *low;
> + uint64_t r0 = 0, r1 = 0;
> +
> + high = (uint32_t *) &fixup_early_pgm_psw.mask;
> + low = high + 1;
> +
> + asm volatile (
> + " epsw %0,%1\n"
> + " st %0,%[high]\n"
> + " st %1,%[low]\n"

What's all this magic with high and low good for? Looks like high and low
are not used afterwards anymore?

> + " larl %0,nop%=\n"
> + " stg %0,%[addr]\n"
> + " lpsw %[psw]\n"
> + "nop%=: nop\n"
> + : "+&r"(r0), "+&a"(r1), [high] "=&R"(*high), [low] "=&R"(*low)

... also not sure why you need the "&" modifiers here?

> + , [addr] "=&R"(fixup_early_pgm_psw.addr)
> + : [psw] "Q"(psw)
> + : "cc", "memory"
> + );
> +}
> +
> +static void psw_bit_31_32_are_1_0(void)
> +{
> + uint64_t bad_psw = 0x000800015eadbeef;
> +
> + //bit 12 gets inverted when extending to 128-bit PSW

I'd prefer a space after the "//"

> + expected_early_pgm_psw.mask = 0x0000000100000000;
> + expected_early_pgm_psw.addr = 0x000000005eadbeef;
> + expect_early = true;
> + lpsw(bad_psw);
> +}
> +
> +static void bad_alignment(void)
> +{
> + uint32_t words[5] = {0, 0, 0};
> + uint32_t (*bad_aligned)[4];
> +
> + register uint64_t r1 asm("6");
> + register uint64_t r2 asm("7");
> + if (((uintptr_t)&words[0]) & 0xf) {
> + bad_aligned = (uint32_t (*)[4])&words[0];
> + } else {
> + bad_aligned = (uint32_t (*)[4])&words[1];
> + }
> + asm volatile ("lpq %0,%2"
> + : "=r"(r1), "=r"(r2)
> + : "T"(*bad_aligned)
> + );
> +}
> +
> +static void not_even(void)
> +{
> + uint64_t quad[2];
> +
> + register uint64_t r1 asm("7");
> + register uint64_t r2 asm("8");
> + asm volatile (".insn rxy,0xe3000000008f,%0,%2" //lpq %0,%2
> + : "=r"(r1), "=r"(r2)
> + : "T"(quad)
> + );
> +}
> +
> +struct spec_ex_trigger {
> + const char *name;
> + void (*func)(void);
> + bool transactable;
> + void (*fixup)(void);
> +};
> +
> +static const struct spec_ex_trigger spec_ex_triggers[] = {
> + { "psw_bit_31_32_are_1_0", &psw_bit_31_32_are_1_0, false, &fixup_early_pgm_ex},
> + { "bad_alignment", &bad_alignment, true, NULL},
> + { "not_even", &not_even, true, NULL},
> + { NULL, NULL, true, NULL},
> +};
> +
> +struct args {
> + uint64_t iterations;
> + uint64_t max_retries;
> + uint64_t suppress_info;
> + uint64_t max_failures;
> + bool diagnose;
> +};
> +
> +static void test_spec_ex(struct args *args,
> + const struct spec_ex_trigger *trigger)
> +{
> + uint16_t expected_pgm = PGM_INT_CODE_SPECIFICATION;
> + uint16_t pgm;
> + unsigned int i;
> +
> + register_pgm_cleanup_func(trigger->fixup);
> + for (i = 0; i < args->iterations; i++) {
> + expect_pgm_int();
> + trigger->func();
> + pgm = clear_pgm_int();
> + if (pgm != expected_pgm) {
> + report(0,
> + "Program interrupt: expected(%d) == received(%d)",
> + expected_pgm,
> + pgm);
> + return;
> + }
> + }

Maybe it would be nice to "unregister" the cleanup function at the end with
register_pgm_cleanup_func(NULL) ?

> + report(1,
> + "Program interrupt: always expected(%d) == received(%d)",
> + expected_pgm,
> + expected_pgm);
> +}
> +
> +#define TRANSACTION_COMPLETED 4
> +#define TRANSACTION_MAX_RETRIES 5
> +
> +static int __attribute__((nonnull))

Not sure whether that attribute makes much sense with a static function? ...
the compiler has information about the implementation details here, so it
should be able to see that e.g. trigger must be non-NULL anyway?

> +with_transaction(void (*trigger)(void), struct __htm_tdb *diagnose)
> +{
> + int cc;
> +
> + cc = __builtin_tbegin(diagnose);
> + if (cc == _HTM_TBEGIN_STARTED) {
> + trigger();
> + __builtin_tend();
> + return -TRANSACTION_COMPLETED;
> + } else {
> + return -cc;
> + }
> +}
[...]

Thomas