From: Mirela Simonovic <mirela.simonovic@aggios.com>
Timer interrupts must be disabled while the system is suspended to prevent
spurious wake-ups. Suspending the timers involves disabling both the EL1
physical timer and the EL2 hypervisor timer. Resuming consists of raising
the TIMER_SOFTIRQ, which prompts the generic timer code to reprogram the
EL2 timer as needed. Re-enabling of the EL1 timer is left to the entity
that uses it.
Introduce a new helper, disable_physical_timers, to encapsulate disabling
of the physical timers.
Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
---
Changes in V4:
- Rephrased comment and commit message for better clarity
- Created separate function for disabling physical timers
Changes in V3:
- time_suspend and time_resume are now conditionally compiled
under CONFIG_SYSTEM_SUSPEND
---
xen/arch/arm/include/asm/time.h | 5 +++++
xen/arch/arm/time.c | 38 +++++++++++++++++++++++++++------
2 files changed, 37 insertions(+), 6 deletions(-)
diff --git a/xen/arch/arm/include/asm/time.h b/xen/arch/arm/include/asm/time.h
index 49ad8c1a6d..f4fd0c6af5 100644
--- a/xen/arch/arm/include/asm/time.h
+++ b/xen/arch/arm/include/asm/time.h
@@ -108,6 +108,11 @@ void preinit_xen_time(void);
void force_update_vcpu_system_time(struct vcpu *v);
+#ifdef CONFIG_SYSTEM_SUSPEND
+void time_suspend(void);
+void time_resume(void);
+#endif /* CONFIG_SYSTEM_SUSPEND */
+
#endif /* __ARM_TIME_H__ */
/*
* Local variables:
diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
index e74d30d258..ad984fdfdd 100644
--- a/xen/arch/arm/time.c
+++ b/xen/arch/arm/time.c
@@ -303,6 +303,14 @@ static void check_timer_irq_cfg(unsigned int irq, const char *which)
"WARNING: %s-timer IRQ%u is not level triggered.\n", which, irq);
}
+/* Disable physical timers for EL1 and EL2 on the current CPU */
+static inline void disable_physical_timers(void)
+{
+ WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
+ WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
+ isb();
+}
+
/* Set up the timer interrupt on this CPU */
void init_timer_interrupt(void)
{
@@ -310,9 +318,7 @@ void init_timer_interrupt(void)
WRITE_SYSREG64(0, CNTVOFF_EL2); /* No VM-specific offset */
/* Do not let the VMs program the physical timer, only read the physical counter */
WRITE_SYSREG(CNTHCTL_EL2_EL1PCTEN, CNTHCTL_EL2);
- WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
- WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
- isb();
+ disable_physical_timers();
request_irq(timer_irq[TIMER_HYP_PPI], 0, htimer_interrupt,
"hyptimer", NULL);
@@ -330,9 +336,7 @@ void init_timer_interrupt(void)
*/
static void deinit_timer_interrupt(void)
{
- WRITE_SYSREG(0, CNTP_CTL_EL0); /* Disable physical timer */
- WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Disable hypervisor's timer */
- isb();
+ disable_physical_timers();
release_irq(timer_irq[TIMER_HYP_PPI], NULL);
release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
@@ -372,6 +376,28 @@ void domain_set_time_offset(struct domain *d, int64_t time_offset_seconds)
/* XXX update guest visible wallclock time */
}
+#ifdef CONFIG_SYSTEM_SUSPEND
+
+void time_suspend(void)
+{
+ disable_physical_timers();
+}
+
+void time_resume(void)
+{
+ /*
+ * Raising the timer softirq triggers generic code to call reprogram_timer
+ * with the correct timeout (not known here).
+ *
+ * No further action is needed to restore timekeeping after power down,
+ * since the system counter is unaffected. See ARM DDI 0487 L.a, D12.1.2
+ * "The system counter must be implemented in an always-on power domain."
+ */
+ raise_softirq(TIMER_SOFTIRQ);
+}
+
+#endif /* CONFIG_SYSTEM_SUSPEND */
+
static int cpu_time_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
--
2.48.1Hi Mykola,
On 01/09/2025 23:10, Mykola Kvach wrote:
> From: Mirela Simonovic <mirela.simonovic@aggios.com>
>
> Timer interrupts must be disabled while the system is suspended to prevent
> spurious wake-ups.
Yet, you don't seem to disable the virtual interrupt. Can you explain why?
> Suspending the timers involves disabling both the EL1
> physical timer and the EL2 hypervisor timer.
I know this is what Arm is naming the timers. But I would rather s/EL1//
and s/EL2// because the physical timer is also accessible from EL0.
Note that Xen doesn't use or expose the physical timer. So it should
always be disabled at the point "time_suspend()" is called. I am still
ok to disable it just in case though.
> Resuming consists of raising
> the TIMER_SOFTIRQ, which prompts the generic timer code to reprogram the
> EL2 timer as needed. Re-enabling of the EL1 timer is left to the entity
> that uses it.
>
> Introduce a new helper, disable_physical_timers, to encapsulate disabling
> of the physical timers.
>
> Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
> Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
> ---
> Changes in V4:
> - Rephrased comment and commit message for better clarity
> - Created separate function for disabling physical timers
>
> Changes in V3:
> - time_suspend and time_resume are now conditionally compiled
> under CONFIG_SYSTEM_SUSPEND
> ---
> xen/arch/arm/include/asm/time.h | 5 +++++
> xen/arch/arm/time.c | 38 +++++++++++++++++++++++++++------
> 2 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/arm/include/asm/time.h b/xen/arch/arm/include/asm/time.h
> index 49ad8c1a6d..f4fd0c6af5 100644
> --- a/xen/arch/arm/include/asm/time.h
> +++ b/xen/arch/arm/include/asm/time.h
> @@ -108,6 +108,11 @@ void preinit_xen_time(void);
>
> void force_update_vcpu_system_time(struct vcpu *v);
>
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +void time_suspend(void);
> +void time_resume(void);
> +#endif /* CONFIG_SYSTEM_SUSPEND */
> +
> #endif /* __ARM_TIME_H__ */
> /*
> * Local variables:
> diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
> index e74d30d258..ad984fdfdd 100644
> --- a/xen/arch/arm/time.c
> +++ b/xen/arch/arm/time.c
> @@ -303,6 +303,14 @@ static void check_timer_irq_cfg(unsigned int irq, const char *which)
> "WARNING: %s-timer IRQ%u is not level triggered.\n", which, irq);
> }
>
> +/* Disable physical timers for EL1 and EL2 on the current CPU */
The name of the times are "physical timer" and "hypervisor timer".
> +static inline void disable_physical_timers(void)
"Physical is a bit misleading" in this context. All the 3 timers
(virtual, physical, hypervisor) are physical timers. My preference would
be to name this function disable_timers() (assuming you also need to
disable the virtual timer).
> +{
> + WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
> + WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
> + isb();
> +}
> +
> /* Set up the timer interrupt on this CPU */
> void init_timer_interrupt(void)
> {
> @@ -310,9 +318,7 @@ void init_timer_interrupt(void)
> WRITE_SYSREG64(0, CNTVOFF_EL2); /* No VM-specific offset */
> /* Do not let the VMs program the physical timer, only read the physical counter */
> WRITE_SYSREG(CNTHCTL_EL2_EL1PCTEN, CNTHCTL_EL2);
> - WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
> - WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
> - isb();
> + disable_physical_timers();
>
> request_irq(timer_irq[TIMER_HYP_PPI], 0, htimer_interrupt,
> "hyptimer", NULL);
> @@ -330,9 +336,7 @@ void init_timer_interrupt(void)
> */
> static void deinit_timer_interrupt(void)
> {
> - WRITE_SYSREG(0, CNTP_CTL_EL0); /* Disable physical timer */
> - WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Disable hypervisor's timer */
> - isb();
> + disable_physical_timers();
>
> release_irq(timer_irq[TIMER_HYP_PPI], NULL);
> release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
> @@ -372,6 +376,28 @@ void domain_set_time_offset(struct domain *d, int64_t time_offset_seconds)
> /* XXX update guest visible wallclock time */
> }
>
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +
> +void time_suspend(void)
> +{
> + disable_physical_timers();
> +}
> +
> +void time_resume(void)
> +{
> + /*
> + * Raising the timer softirq triggers generic code to call reprogram_timer
> + * with the correct timeout (not known here).
> + *
> + * No further action is needed to restore timekeeping after power down,
> + * since the system counter is unaffected. See ARM DDI 0487 L.a, D12.1.2
> + * "The system counter must be implemented in an always-on power domain."
> + */
> + raise_softirq(TIMER_SOFTIRQ);
I think we should add a comment about the physical timer.
> +}
> +
> +#endif /* CONFIG_SYSTEM_SUSPEND */
> +
> static int cpu_time_callback(struct notifier_block *nfb,
> unsigned long action,
> void *hcpu)Cheers,
--
Julien Grall
Hi,
Mykola Kvach <xakep.amatop@gmail.com> writes:
> From: Mirela Simonovic <mirela.simonovic@aggios.com>
>
> Timer interrupts must be disabled while the system is suspended to prevent
> spurious wake-ups. Suspending the timers involves disabling both the EL1
> physical timer and the EL2 hypervisor timer. Resuming consists of raising
> the TIMER_SOFTIRQ, which prompts the generic timer code to reprogram the
> EL2 timer as needed. Re-enabling of the EL1 timer is left to the entity
> that uses it.
>
> Introduce a new helper, disable_physical_timers, to encapsulate disabling
> of the physical timers.
>
> Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
> Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@epam.com>
> ---
> Changes in V4:
> - Rephrased comment and commit message for better clarity
> - Created separate function for disabling physical timers
>
> Changes in V3:
> - time_suspend and time_resume are now conditionally compiled
> under CONFIG_SYSTEM_SUSPEND
> ---
> xen/arch/arm/include/asm/time.h | 5 +++++
> xen/arch/arm/time.c | 38 +++++++++++++++++++++++++++------
> 2 files changed, 37 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/arm/include/asm/time.h b/xen/arch/arm/include/asm/time.h
> index 49ad8c1a6d..f4fd0c6af5 100644
> --- a/xen/arch/arm/include/asm/time.h
> +++ b/xen/arch/arm/include/asm/time.h
> @@ -108,6 +108,11 @@ void preinit_xen_time(void);
>
> void force_update_vcpu_system_time(struct vcpu *v);
>
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +void time_suspend(void);
> +void time_resume(void);
> +#endif /* CONFIG_SYSTEM_SUSPEND */
> +
> #endif /* __ARM_TIME_H__ */
> /*
> * Local variables:
> diff --git a/xen/arch/arm/time.c b/xen/arch/arm/time.c
> index e74d30d258..ad984fdfdd 100644
> --- a/xen/arch/arm/time.c
> +++ b/xen/arch/arm/time.c
> @@ -303,6 +303,14 @@ static void check_timer_irq_cfg(unsigned int irq, const char *which)
> "WARNING: %s-timer IRQ%u is not level triggered.\n", which, irq);
> }
>
> +/* Disable physical timers for EL1 and EL2 on the current CPU */
> +static inline void disable_physical_timers(void)
> +{
> + WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
> + WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
> + isb();
> +}
> +
> /* Set up the timer interrupt on this CPU */
> void init_timer_interrupt(void)
> {
> @@ -310,9 +318,7 @@ void init_timer_interrupt(void)
> WRITE_SYSREG64(0, CNTVOFF_EL2); /* No VM-specific offset */
> /* Do not let the VMs program the physical timer, only read the physical counter */
> WRITE_SYSREG(CNTHCTL_EL2_EL1PCTEN, CNTHCTL_EL2);
> - WRITE_SYSREG(0, CNTP_CTL_EL0); /* Physical timer disabled */
> - WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Hypervisor's timer disabled */
> - isb();
> + disable_physical_timers();
>
> request_irq(timer_irq[TIMER_HYP_PPI], 0, htimer_interrupt,
> "hyptimer", NULL);
> @@ -330,9 +336,7 @@ void init_timer_interrupt(void)
> */
> static void deinit_timer_interrupt(void)
> {
> - WRITE_SYSREG(0, CNTP_CTL_EL0); /* Disable physical timer */
> - WRITE_SYSREG(0, CNTHP_CTL_EL2); /* Disable hypervisor's timer */
> - isb();
> + disable_physical_timers();
>
> release_irq(timer_irq[TIMER_HYP_PPI], NULL);
> release_irq(timer_irq[TIMER_VIRT_PPI], NULL);
> @@ -372,6 +376,28 @@ void domain_set_time_offset(struct domain *d, int64_t time_offset_seconds)
> /* XXX update guest visible wallclock time */
> }
>
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +
> +void time_suspend(void)
> +{
> + disable_physical_timers();
> +}
> +
> +void time_resume(void)
> +{
> + /*
> + * Raising the timer softirq triggers generic code to call reprogram_timer
> + * with the correct timeout (not known here).
> + *
> + * No further action is needed to restore timekeeping after power down,
> + * since the system counter is unaffected. See ARM DDI 0487 L.a, D12.1.2
> + * "The system counter must be implemented in an always-on power domain."
> + */
> + raise_softirq(TIMER_SOFTIRQ);
> +}
> +
> +#endif /* CONFIG_SYSTEM_SUSPEND */
> +
> static int cpu_time_callback(struct notifier_block *nfb,
> unsigned long action,
> void *hcpu)
--
WBR, Volodymyr
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