On 29.04.20 16:35, Janosch Frank wrote:
> Sigp orders are not necessarily finished when the processor finished
> the sigp instruction. We need to poll if the order has been finished
> before we continue.
>
> For (re)start and stop we already use sigp sense running and sigp
> sense loops. But we still lack completion checks for stop and store
> status, as well as the cpu resets.
>
> Let's add them.
>
> KVM currently needs a workaround for the stop and store status test,
> since KVM's SIGP Sense implementation doesn't honor pending SIGPs at
> it should. Hopefully we can fix that in the future.
>
> Signed-off-by: Janosch Frank <frankja@xxxxxxxxxxxxx>
> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx>
> ---
> lib/s390x/smp.c | 9 +++++++++
> lib/s390x/smp.h | 1 +
> s390x/smp.c | 12 ++++++++++--
> 3 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
> index 6ef0335..8628a3d 100644
> --- a/lib/s390x/smp.c
> +++ b/lib/s390x/smp.c
> @@ -49,6 +49,14 @@ struct cpu *smp_cpu_from_addr(uint16_t addr)
> return NULL;
> }
>
> +void smp_cpu_wait_for_completion(uint16_t addr)
> +{
> + uint32_t status;
> +
> + /* Loops when cc == 2, i.e. when the cpu is busy with a sigp order */
> + sigp_retry(1, SIGP_SENSE, 0, &status);
> +}
> +
> bool smp_cpu_stopped(uint16_t addr)
> {
> uint32_t status;
> @@ -100,6 +108,7 @@ int smp_cpu_stop_store_status(uint16_t addr)
>
> spin_lock(&lock);
> rc = smp_cpu_stop_nolock(addr, true);
> + smp_cpu_wait_for_completion(addr);
> spin_unlock(&lock);
> return rc;
> }
> diff --git a/lib/s390x/smp.h b/lib/s390x/smp.h
> index ce63a89..a8b98c0 100644
> --- a/lib/s390x/smp.h
> +++ b/lib/s390x/smp.h
> @@ -45,6 +45,7 @@ int smp_cpu_restart(uint16_t addr);
> int smp_cpu_start(uint16_t addr, struct psw psw);
> int smp_cpu_stop(uint16_t addr);
> int smp_cpu_stop_store_status(uint16_t addr);
> +void smp_cpu_wait_for_completion(uint16_t addr);
> int smp_cpu_destroy(uint16_t addr);
> int smp_cpu_setup(uint16_t addr, struct psw psw);
> void smp_teardown(void);
> diff --git a/s390x/smp.c b/s390x/smp.c
> index c7ff0ee..bad2131 100644
> --- a/s390x/smp.c
> +++ b/s390x/smp.c
> @@ -75,7 +75,12 @@ static void test_stop_store_status(void)
> lc->prefix_sa = 0;
> lc->grs_sa[15] = 0;
> smp_cpu_stop_store_status(1);
> - mb();
> + /*
> + * This loop is workaround for KVM not reporting cc 2 for SIGP
> + * sense if a stop and store status is pending.
> + */
> + while (!lc->prefix_sa)
> + mb();
> report(lc->prefix_sa == (uint32_t)(uintptr_t)cpu->lowcore, "prefix");
> report(lc->grs_sa[15], "stack");
> report(smp_cpu_stopped(1), "cpu stopped");
> @@ -85,7 +90,8 @@ static void test_stop_store_status(void)
> lc->prefix_sa = 0;
> lc->grs_sa[15] = 0;
> smp_cpu_stop_store_status(1);
> - mb();
> + while (!lc->prefix_sa)
> + mb();
> report(lc->prefix_sa == (uint32_t)(uintptr_t)cpu->lowcore, "prefix");
> report(lc->grs_sa[15], "stack");
> report_prefix_pop();
> @@ -215,6 +221,7 @@ static void test_reset_initial(void)
> wait_for_flag();
>
> sigp_retry(1, SIGP_INITIAL_CPU_RESET, 0, NULL);
> + smp_cpu_wait_for_completion(1);
^ is this really helpful? The next order already properly synchronizes, no?
> sigp(1, SIGP_STORE_STATUS_AT_ADDRESS, (uintptr_t)status, NULL);
>
> report_prefix_push("clear");
> @@ -265,6 +272,7 @@ static void test_reset(void)
> smp_cpu_start(1, psw);
>
> sigp_retry(1, SIGP_CPU_RESET, 0, NULL);
> + smp_cpu_wait_for_completion(1);
Isn't this racy for KVM as well?
I would have expected a loop until it is actually stopped.
> report(smp_cpu_stopped(1), "cpu stopped");
>
> set_flag(0);
>
--
Thanks,
David / dhildenb
