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ARM: CORTEX M, PRIMASK does not disable interrupts
qemu version 0.15.1
but the same code is in qemu 1.0
"CPSID I" does not disable interrupts for CORTEX M3
if (interrupt_request & CPU_INTERRUPT_HARD
&& ((IS_M(env) && env->regs[15] < 0xfffffff0)
|| !(env->uncached_cpsr & CPSR_I))) {
env->exception_index = EXCP_IRQ;
do_interrupt(env);
next_tb = 0;
}
do_interrupt() will be executed even if (env->uncached_cpsr & CPSR_I) == 1 , disable interrupt bit set.
then changed to:
if (interrupt_request & CPU_INTERRUPT_HARD
&& !(env->uncached_cpsr & CPSR_I)
&& (IS_M(env) ? env->regs[15] < 0xfffffff0: 1) ) {
env->exception_index = EXCP_IRQ;
do_interrupt(env);
next_tb = 0;
}
works
This change changes the behaviour for non-M-profile cores, which looks wrong.
See discussion in this mailing list thread where a similar patch was suggested:
http://lists.gnu.org/archive/html/qemu-devel/2011-06/msg00500.html
M profile interrupt handling is known-broken. I'm not accepting any patches in this area unless they come attached to a decent explanation of why they are the correct change to make and show some evidence of the whole problem having been considered.
> This change changes the behaviour for non-M-profile cores
...or maybe not: I was confused by the resemblance to that other patch. I still think one-line fixes are unlikely to be the right approach here, though.
This long-standing bug has been fixed by the rewrite of the M-profile exception handling for QEMU 2.9.
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