Re: [kvm-unit-tests PATCH v1 2/3] s390x: add extint loop test

Janosch Frank
2022-07-04T08:32:30Z

On 6/30/22 13:30, Nico Boehr wrote:
> The CPU timer interrupt stays pending as long as the CPU timer value is
> negative. This can lead to interruption loops when the ext_new_psw mask
> has external interrupts enabled.
>
> QEMU is able to detect this situation and panic the guest, so add a test
> for it.
>
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> ---
> s390x/Makefile | 1 +
> s390x/extint-loop.c | 64 +++++++++++++++++++++++++++++++++++++++++++++
> s390x/unittests.cfg | 4 +++
> 3 files changed, 69 insertions(+)
> create mode 100644 s390x/extint-loop.c
>
> diff --git a/s390x/Makefile b/s390x/Makefile
> index efd5e0c13102..92a020234c9f 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -34,6 +34,7 @@ tests += $(TEST_DIR)/migration.elf
> tests += $(TEST_DIR)/pv-attest.elf
> tests += $(TEST_DIR)/migration-cmm.elf
> tests += $(TEST_DIR)/migration-skey.elf
> +tests += $(TEST_DIR)/extint-loop.elf

I'd suggest giving these tests a "panic" prefix. panic-loop-extint.c
panic-loop-pgm.c

>
> pv-tests += $(TEST_DIR)/pv-diags.elf
>
> diff --git a/s390x/extint-loop.c b/s390x/extint-loop.c
> new file mode 100644
> index 000000000000..5276d86a156f
> --- /dev/null
> +++ b/s390x/extint-loop.c
> @@ -0,0 +1,64 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * External interrupt loop test
> + *
> + * Copyright IBM Corp. 2022
> + *
> + * Authors:
> + * Nico Boehr <nrb@linux.ibm.com>
> + */
> +#include <libcflat.h>
> +#include <asm/interrupt.h>
> +#include <asm/barrier.h>
> +#include <asm/time.h>
> +
> +static void ext_int_handler(void)
> +{
> + /*
> + * return to ext_old_psw. This gives us the chance to print the return_fail
> + * in case something goes wrong.
> + */
> + asm volatile (
> + "lpswe %[ext_old_psw]\n"
> + :
> + : [ext_old_psw] "Q"(lowcore.ext_old_psw)
> + : "memory"
> + );
> +}
> +
> +static void start_cpu_timer(int64_t timeout_ms)

cpu_timer_set

> +{
> +#define CPU_TIMER_US_SHIFT 12

The clock and the timer use the same shift so maybe we can rename or
reuse time.h constants?

We could rename STCK_SHIFT_US to TIMING_S390_SHIFT_US since we need that
for the TOD, todcmp and cputimer.

> + int64_t timer_value = (timeout_ms * 1000) << CPU_TIMER_US_SHIFT;
> + asm volatile (
> + "spt %[timer_value]\n"
> + :
> + : [timer_value] "Q" (timer_value)
> + );
> +}
> +
> +int main(void)
> +{
> + struct psw ext_new_psw_orig;
> +
> + report_prefix_push("extint-loop");

This is a QEMU only test so I think we should fence other hypervisors.

> +
> + ext_new_psw_orig = lowcore.ext_new_psw;
> + lowcore.ext_new_psw.addr = (uint64_t)ext_int_handler;
> + lowcore.ext_new_psw.mask |= PSW_MASK_EXT;
> +
> + load_psw_mask(extract_psw_mask() | PSW_MASK_EXT);
> + ctl_set_bit(0, CTL0_CLOCK_COMPARATOR);
> +
> + start_cpu_timer(1);
> +
> + mdelay(2000);
> +
> + /* restore previous ext_new_psw so QEMU can properly terminate */
> + lowcore.ext_new_psw = ext_new_psw_orig;
> +
> + report_fail("survived extint loop");
> +
> + report_prefix_pop();
> + return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index 8e52f560bb1e..7d408f2d5310 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -184,3 +184,7 @@ groups = migration
> [migration-skey]
> file = migration-skey.elf
> groups = migration
> +
> +[extint-loop]
> +file = extint-loop.elf
> +groups = panic