Re: [Minios-devel] [UNIKRAFT RFC PATCH 2/2] plat/common: Add a trap function to handle Arm64 irq trap

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 20/11/2018 10:18, Jianyong Wu wrote:
> From: Wei Chen <wei.chen@xxxxxxx>
>
> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> ---
>   plat/common/arm/traps.c   | 25 +++++++++++++++++++++++++
>   plat/kvm/arm/exceptions.S | 10 +++++++++-
>   2 files changed, 34 insertions(+), 1 deletion(-)
>
> diff --git a/plat/common/arm/traps.c b/plat/common/arm/traps.c
> index 43235be..df1b5c7 100644
> --- a/plat/common/arm/traps.c
> +++ b/plat/common/arm/traps.c
> @@ -23,6 +23,7 @@
>   #include <string.h>
>   #include <uk/print.h>
>   #include <uk/assert.h>
> +#include <arm/gic-v2.h>
>   
>   static const char *exception_modes[]= {
>         "Synchronous Abort",
> @@ -68,3 +69,27 @@ void trap_el1_sync(struct __regs *regs, uint64_t far)
>         dump_registers(regs, far);
>         ukplat_crash();
>   }
> +
> +void trap_el1_irq(struct __regs *regs, uint64_t far)
> +{
> +       uint32_t stat, irq;
> +
> +       do {
> +               stat = gic_ack_irq();
> +               irq = stat & GICC_IAR_INTID_MASK;
> +
> +               uk_printd(DLVL_CRIT, "Unikraft: EL1 IRQ#%d trap caught\n", irq);
> +
> +               /*
> +                * TODO: Hanle IPI&SGI interrupts here
> +                */
> +               if (irq < GIC_MAX_IRQ) {
> +                       _ukplat_irq_handle((unsigned long)irq);
> +                       gic_eoi_irq(stat);
> +                       isb();
Can you explain why you need an isb() after gic_eoi_irq?

On the previous patch the isb() was just before _ukplat_irq_handle(). The 
position made sense because you want to ensure that all the system registers are 
synchronized after receiving the interrupt (see [1]).
Cheers,

[1] https://lists.xenproject.org/archives/html/xen-devel/2018-10/msg01802.html

--
Julien Grall

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