Re: [kvm-unit-tests PATCH v4 3/3] s390x: smp: add tests for calls in wait state

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

On Wed, 10 Aug 2022 09:46:16 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> When the SIGP interpretation facility is in use a SIGP external call to
> a waiting CPU will result in an exit of the calling cpu. For non-pv
> guests it's a code 56 (partial execution) exit otherwise its a code 108
> (secure instruction notification) exit. Those exits are handled
> differently from a normal SIGP instruction intercept that happens
> without interpretation and hence need to be tested.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  s390x/smp.c | 97 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 97 insertions(+)
> 
> diff --git a/s390x/smp.c b/s390x/smp.c
> index 5a269087581f..91f3e3bcc12a 100644
> --- a/s390x/smp.c
> +++ b/s390x/smp.c
> @@ -356,6 +356,102 @@ static void test_calls(void)
>  	}
>  }
>  
> +static void call_in_wait_ext_int_fixup(struct stack_frame_int *stack)
> +{
> +	/* Clear wait bit so we don't immediately wait again after the fixup */
> +	lowcore.ext_old_psw.mask &= ~PSW_MASK_WAIT;
> +}
> +
> +static void call_in_wait_setup(void)
> +{
> +	expect_ext_int();
> +	ctl_set_bit(0, current_sigp_call_case->cr0_bit);
> +	register_ext_cleanup_func(call_in_wait_ext_int_fixup);
> +
> +	set_flag(1);
> +}
> +
> +static void call_in_wait_received(void)
> +{
> +	report(lowcore.ext_int_code == current_sigp_call_case->ext_int_expected_type, "received");
> +
> +	set_flag(1);
> +}
> +
> +static void call_in_wait_cleanup(void)
> +{
> +	ctl_clear_bit(0, current_sigp_call_case->cr0_bit);
> +	register_ext_cleanup_func(NULL);
> +
> +	set_flag(1);
> +}
> +
> +static void test_calls_in_wait(void)
> +{
> +	int i;
> +	struct psw psw;
> +
> +	report_prefix_push("psw wait");
> +	for (i = 0; i < ARRAY_SIZE(cases_sigp_call); i++) {
> +		current_sigp_call_case = &cases_sigp_call[i];
> +
> +		report_prefix_push(current_sigp_call_case->name);
> +		if (!current_sigp_call_case->supports_pv && uv_os_is_guest()) {
> +			report_skip("Not supported under PV");
> +			report_prefix_pop();
> +			continue;
> +		}
> +
> +		/* Let the secondary CPU setup the external mask and the external interrupt cleanup function */
> +		set_flag(0);
> +		psw.mask = extract_psw_mask();
> +		psw.addr = (unsigned long)call_in_wait_setup;
> +		smp_cpu_start(1, psw);
> +
> +		/* Wait until the receiver has finished setup */
> +		wait_for_flag();
> +		set_flag(0);
> +
> +		/*
> +		 * To avoid races, we need to know that the secondary CPU has entered wait,
> +		 * but the architecture provides no way to check whether the secondary CPU
> +		 * is in wait.
> +		 *
> +		 * But since a waiting CPU is considered operating, simply stop the CPU, set
> +		 * up the restart new PSW mask in wait, send the restart interrupt and then
> +		 * wait until the CPU becomes operating (done by smp_cpu_start).
> +		 */
> +		smp_cpu_stop(1);
> +		psw.mask = extract_psw_mask() | PSW_MASK_EXT | PSW_MASK_WAIT;
> +		psw.addr = (unsigned long)call_in_wait_received;
> +		smp_cpu_start(1, psw);
> +
> +		smp_sigp(1, current_sigp_call_case->call, 0, NULL);
> +
> +		/* Wait until the receiver has handled the call */
> +		wait_for_flag();
> +		smp_cpu_stop(1);
> +		set_flag(0);
> +
> +		/*
> +		 * Now clean up the mess we have left behind. If the cleanup
> +		 * were part of call_in_wait_received we would not get a chance
> +		 * to catch an interrupt that is presented twice since we would
> +		 * disable the external call on the first interrupt.
> +		 */
> +		psw.mask = extract_psw_mask();
> +		psw.addr = (unsigned long)call_in_wait_cleanup;
> +		smp_cpu_start(1, psw);
> +
> +		/* Wait until the cleanup has been completed */
> +		wait_for_flag();
> +		smp_cpu_stop(1);
> +
> +		report_prefix_pop();
> +	}
> +	report_prefix_pop();
> +}
> +
>  static void test_sense_running(void)
>  {
>  	report_prefix_push("sense_running");
> @@ -474,6 +570,7 @@ int main(void)
>  	test_store_status();
>  	test_set_prefix();
>  	test_calls();
> +	test_calls_in_wait();
>  	test_sense_running();
>  	test_reset();
>  	test_reset_initial();