On Fri, 22 Jul 2022 08:00:42 +0200
Nico Boehr <nrb@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx>
> Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
> ---
> s390x/Makefile | 1 +
> s390x/panic-loop-extint.c | 60 +++++++++++++++++++++++++++++++++++++++
> s390x/unittests.cfg | 6 ++++
> 3 files changed, 67 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..d3a3f06d9a34
> --- /dev/null
> +++ b/s390x/panic-loop-extint.c
> @@ -0,0 +1,60 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * External interrupt loop test
> + *
> + * Copyright IBM Corp. 2022
> + *
> + * Authors:
> + * Nico Boehr <nrb@xxxxxxxxxxxxx>
> + */
> +#include <libcflat.h>
> +#include <asm/interrupt.h>
> +#include <asm/barrier.h>
> +#include <asm/time.h>
> +#include <hardware.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"
> + );
> +}
why should ext_old_psw contain a good PSW? wouldn't it contain the
PSW at the time of the interrupt? (which in this case is the new PSW)
but this should never happen anyway, right?
> +
> +int main(void)
> +{
> + struct psw ext_new_psw_orig;
> +
> + report_prefix_push("panic-loop-extint");
> +
> + if (!host_is_qemu() || host_is_tcg()) {
> + report_skip("QEMU-KVM-only test");
> + goto out;
> + }
> +
> + 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);
> +
> + cpu_timer_set_ms(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");
> +
> +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
