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Re: [Qemu-arm] [PATCH 6/9] armv7m: Escalate exceptions to HardFault if n
From: |
Alex Bennée |
Subject: |
Re: [Qemu-arm] [PATCH 6/9] armv7m: Escalate exceptions to HardFault if necessary |
Date: |
Wed, 15 Feb 2017 14:15:49 +0000 |
User-agent: |
mu4e 0.9.19; emacs 25.2.3 |
Peter Maydell <address@hidden> writes:
> From: Michael Davidsaver <address@hidden>
>
> The v7M exception architecture requires that if a synchronous
> exception cannot be taken immediately (because it is disabled
> or at too low a priority) then it should be escalated to
> HardFault (and the HardFault exception is then taken).
> Implement this escalation logic.
>
> Signed-off-by: Michael Davidsaver <address@hidden>
> [PMM: extracted from another patch]
> Signed-off-by: Peter Maydell <address@hidden>
Reviewed-by: Alex Bennée <address@hidden>
> ---
> hw/intc/armv7m_nvic.c | 53
> +++++++++++++++++++++++++++++++++++++++++++++++++++
> target/arm/helper.c | 2 --
> 2 files changed, 53 insertions(+), 2 deletions(-)
>
> diff --git a/hw/intc/armv7m_nvic.c b/hw/intc/armv7m_nvic.c
> index 3d77cbf..2eaac3d 100644
> --- a/hw/intc/armv7m_nvic.c
> +++ b/hw/intc/armv7m_nvic.c
> @@ -334,6 +334,59 @@ void armv7m_nvic_set_pending(void *opaque, int irq)
>
> vec = &s->vectors[irq];
> trace_nvic_set_pending(irq, vec->enabled, vec->prio);
> +
> +
> + if (irq >= ARMV7M_EXCP_HARD && irq < ARMV7M_EXCP_PENDSV) {
> + /* If a synchronous exception is pending then it may be
> + * escalated to HardFault if:
> + * * it is equal or lower priority to current execution
> + * * it is disabled
> + * (ie we need to take it immediately but we can't do so).
> + * Asynchronous exceptions (and interrupts) simply remain pending.
> + *
> + * For QEMU, we don't have any imprecise (asynchronous) faults,
> + * so we can assume that PREFETCH_ABORT and DATA_ABORT are always
> + * synchronous.
> + * Debug exceptions are awkward because only Debug exceptions
> + * resulting from the BKPT instruction should be escalated,
> + * but we don't currently implement any Debug exceptions other
> + * than those that result from BKPT, so we treat all debug exceptions
> + * as needing escalation.
> + *
> + * This all means we can identify whether to escalate based only on
> + * the exception number and don't (yet) need the caller to explicitly
> + * tell us whether this exception is synchronous or not.
> + */
> + int running = nvic_exec_prio(s);
> + bool escalate = false;
> +
> + if (vec->prio >= running) {
> + trace_nvic_escalate_prio(irq, vec->prio, running);
> + escalate = true;
> + } else if (!vec->enabled) {
> + trace_nvic_escalate_disabled(irq);
> + escalate = true;
> + }
> +
> + if (escalate) {
> + if (running < 0) {
> + /* We want to escalate to HardFault but we can't take a
> + * synchronous HardFault at this point either. This is a
> + * Lockup condition due to a guest bug. We don't model
> + * Lockup, so report via cpu_abort() instead.
> + */
> + cpu_abort(&s->cpu->parent_obj,
> + "Lockup: can't escalate %d to HardFault "
> + "(current priority %d)\n", irq, running);
> + }
> +
> + /* We can do the escalation, so we take HardFault instead */
> + irq = ARMV7M_EXCP_HARD;
> + vec = &s->vectors[irq];
> + s->cpu->env.v7m.hfsr |= R_V7M_HFSR_FORCED_MASK;
> + }
> + }
> +
> if (!vec->pending) {
> vec->pending = 1;
> nvic_irq_update(s);
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index c23df1b..6c86eac 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6067,8 +6067,6 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
>
> /* For exceptions we just mark as pending on the NVIC, and let that
> handle it. */
> - /* TODO: Need to escalate if the current priority is higher than the
> - one we're raising. */
> switch (cs->exception_index) {
> case EXCP_UDEF:
> armv7m_nvic_set_pending(env->nvic, ARMV7M_EXCP_USAGE);
--
Alex Bennée
- [Qemu-arm] [PATCH 0/9] Rewrite NVIC to not depend on the GIC, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 9/9] armv7m: VECTCLRACTIVE and VECTRESET are UNPREDICTABLE, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 8/9] armv7m: Simpler and faster exception start, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 7/9] armv7m: Remove unused armv7m_nvic_acknowledge_irq() return value, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 6/9] armv7m: Escalate exceptions to HardFault if necessary, Peter Maydell, 2017/02/02
- Re: [Qemu-arm] [PATCH 6/9] armv7m: Escalate exceptions to HardFault if necessary,
Alex Bennée <=
- [Qemu-arm] [PATCH 4/9] armv7m: Fix condition check for taking exceptions, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 2/9] armv7m: Implement reading and writing of PRIGROUP, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 5/9] arm: gic: Remove references to NVIC, Peter Maydell, 2017/02/02
- [Qemu-arm] [PATCH 1/9] armv7m: Rename nvic_state to NVICState, Peter Maydell, 2017/02/02