Hi All,
I am trying to run a RTOS as a guest on a OMAP5432 evm and am seeing a spurious
interrupt problem when programming the virtual timer interrupts. My RTOS test
case uses the A15 Virtual timer to create a timer instance. Once programmed, the
virtual timer interrupt is injected into my guest's virtual CPU interface as
expected and the interrupt is also forwarded to my guest. At this point, my
RTOS's IRQ service routine is invoked which among other things reads
GICV_IAR register to acknowledge the interrupt and then re-enables IRQs (to
support nested interrupts) before calling the timer handler which is suppose to
program the CNTV_CVAL register for the next tick. I notice that as soon as
interrupts are re-enabled, the ISR is interrupted and the IRQ service routine is
called again. However, this time GICV_IAR register returns 1023. Once the ISR
detects a spurious interrupt and returns, it gets interrupted again with another
spurious interrupt. I see that the guest is flooded with these spurious
interrupts and is not able to complete servicing the original virtual timer
interrupt.
If I disable nesting (i.e. do not re-enable IRQs in my service routine),
everything works as expected which makes me wonder if the spurious interrupts
are related to the virtual timer. I tried adding a debug print in
vgic_vcpu_inject_irq to see if xen was injecting some high priority interrupt
but found that xen only injects a single virtual timer PPI.
Has anyone seen this behavior or has suggestions on how to debug this problem
further ?
Thanks,
Ashish
My xen build info:
I am using xen 4.5-unstable and am at 8cfc8e520679e029bed51ccc2540a136fc0fbd9b
commit. My RTOS image is an elf image and in order to make elf loading work, I
have also applied the following 2 patches as suggested in this thread ->
http://lists.freebsd.org/pipermail/freebsd-xen/2014-January/001974.html. These
patches should not affect the gic behavior but thought I should mention them
just in case:
https://patches.linaro.org/22228/
https://patches.linaro.org/22227/
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