Re: [kvm-unit-tests PATCH v4 3/4] s390x: add extint loop test

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

On Fri, 12 Aug 2022 08:21:50 +0200
Nico Boehr <nrb@linux.ibm.com> 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>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>  s390x/Makefile            |  1 +
>  s390x/panic-loop-extint.c | 59 +++++++++++++++++++++++++++++++++++++++
>  s390x/unittests.cfg       |  6 ++++
>  3 files changed, 66 insertions(+)
>  create mode 100644 s390x/panic-loop-extint.c
> 
> diff --git a/s390x/Makefile b/s390x/Makefile
> index efd5e0c13102..e4649da50d9d 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)/panic-loop-extint.elf
>  
>  pv-tests += $(TEST_DIR)/pv-diags.elf
>  
> diff --git a/s390x/panic-loop-extint.c b/s390x/panic-loop-extint.c
> new file mode 100644
> index 000000000000..79d3f84a89ff
> --- /dev/null
> +++ b/s390x/panic-loop-extint.c
> @@ -0,0 +1,59 @@
> +/* 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>
> +#include <hardware.h>
> +#include <bitops.h>
> +
> +static void ext_int_cleanup(struct stack_frame_int *stack)
> +{
> +	/*
> +	 * Since we form a loop of ext interrupts, this code should never be
> +	 * executed. In case it is executed, something went wrong and we want to
> +	 * print a failure.
> +	 *
> +	 * Because the CPU timer subclass mask is still enabled, the CPU timer
> +	 * interrupt will fire every time we enable external interrupts,
> +	 * preventing us from printing the failure on the console. To avoid
> +	 * this, clear the CPU timer subclass mask here.
> +	 */
> +	stack->crs[0] &= ~BIT(CTL0_CPU_TIMER);
> +}
> +
> +int main(void)
> +{
> +	report_prefix_push("panic-loop-extint");
> +
> +	if (!host_is_qemu() || host_is_tcg()) {
> +		report_skip("QEMU-KVM-only test");
> +		goto out;
> +	}
> +
> +	expect_ext_int();
> +	lowcore.ext_new_psw.mask |= PSW_MASK_EXT;
> +
> +	load_psw_mask(extract_psw_mask() | PSW_MASK_EXT);

you can use the recently introduced psw_mask_set_bits(PSW_MASK_EXT)

> +
> +	register_ext_cleanup_func(ext_int_cleanup);
> +
> +	cpu_timer_set_ms(10);
> +	ctl_set_bit(0, CTL0_CPU_TIMER);
> +	mdelay(2000);
> +
> +	register_ext_cleanup_func(NULL);
> +
> +	report_fail("survived extint loop");
> +
> +out:
> +	report_prefix_pop();
> +	return report_summary();
> +}
> diff --git a/s390x/unittests.cfg b/s390x/unittests.cfg
> index f7b1fc3dbca1..b1b25f118ff6 100644
> --- a/s390x/unittests.cfg
> +++ b/s390x/unittests.cfg
> @@ -185,3 +185,9 @@ groups = migration
>  [migration-skey]
>  file = migration-skey.elf
>  groups = migration
> +
> +[panic-loop-extint]
> +file = panic-loop-extint.elf
> +groups = panic
> +accel = kvm
> +timeout = 5