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armv7m: Fix condition check for taking exceptions

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The M profile condition for when we can take a pending exception or
interrupt is not the same as that for A/R profile.  The code
originally copied from the A/R profile version of the
cpu_exec_interrupt function only worked by chance for the
very simple case of exceptions being masked by PRIMASK.
Replace it with a call to a function in the NVIC code that
correctly compares the priority of the pending exception
against the current execution priority of the CPU.

[Michael Davidsaver's patchset had a patch to do something
similar but the implementation ended up being a rewrite.]

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
This commit is contained in:
Peter Maydell 2017-02-28 12:08:17 +00:00
parent da6d674e50
commit 7ecdaa4a96
3 changed files with 23 additions and 8 deletions
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7
hw/intc/armv7m_nvic.c
View File

@ -286,6 +286,13 @@ static inline int nvic_exec_prio(NVICState *s)
return MIN(running, s->exception_prio);
}
bool armv7m_nvic_can_take_pending_exception(void *opaque)
{
NVICState *s = opaque;
return nvic_exec_prio(s) > nvic_pending_prio(s);
}
/* caller must call nvic_irq_update() after this */
static void set_prio(NVICState *s, unsigned irq, uint8_t prio)
{

16
target/arm/cpu.c
View File

@ -338,13 +338,6 @@ static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
CPUARMState *env = &cpu->env;
bool ret = false;
if (interrupt_request & CPU_INTERRUPT_FIQ
&& !(env->daif & PSTATE_F)) {
cs->exception_index = EXCP_FIQ;
cc->do_interrupt(cs);
ret = true;
}
/* ARMv7-M interrupt return works by loading a magic value
* into the PC. On real hardware the load causes the
* return to occur. The qemu implementation performs the
@ -354,9 +347,16 @@ static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
* the stack if an interrupt occurred at the wrong time.
* We avoid this by disabling interrupts when
* pc contains a magic address.
*
* ARMv7-M interrupt masking works differently than -A or -R.
* There is no FIQ/IRQ distinction. Instead of I and F bits
* masking FIQ and IRQ interrupts, an exception is taken only
* if it is higher priority than the current execution priority
* (which depends on state like BASEPRI, FAULTMASK and the
* currently active exception).
*/
if (interrupt_request & CPU_INTERRUPT_HARD
&& !(env->daif & PSTATE_I)
&& (armv7m_nvic_can_take_pending_exception(env->nvic))
&& (env->regs[15] < 0xfffffff0)) {
cs->exception_index = EXCP_IRQ;
cc->do_interrupt(cs);

8
target/arm/cpu.h
View File

@ -1356,6 +1356,14 @@ uint32_t arm_phys_excp_target_el(CPUState *cs, uint32_t excp_idx,
uint32_t cur_el, bool secure);
/* Interface between CPU and Interrupt controller. */
#ifndef CONFIG_USER_ONLY
bool armv7m_nvic_can_take_pending_exception(void *opaque);
#else
static inline bool armv7m_nvic_can_take_pending_exception(void *opaque)
{
return true;
}
#endif
void armv7m_nvic_set_pending(void *opaque, int irq);
int armv7m_nvic_acknowledge_irq(void *opaque);
void armv7m_nvic_complete_irq(void *opaque, int irq);