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

["Jianyong Wu (Arm Technology China)" <Jianyong.Wu@xxxxxxx>]

Hi,


> -----Original Message-----
> From: Julien Grall <julien.grall@xxxxxxx>
> Sent: Monday, November 12, 2018 7:06 PM
> To: Jianyong Wu (Arm Technology China) <Jianyong.Wu@xxxxxxx>; minios-
> devel@xxxxxxxxxxxxxxxxxxxx; simon.kuenzer@xxxxxxxxx
> Cc: Kaly Xin (Arm Technology China) <Kaly.Xin@xxxxxxx>; nd
> <nd@xxxxxxx>; Wei Chen (Arm Technology China) <Wei.Chen@xxxxxxx>
> Subject: Re: [Minios-devel] [UNIKRAFT RFC PATCH 2/2] plat/common: Add a
> trap function to handle Arm64 irq trap
> 
> 
> 
> On 11/10/18 2:02 PM, Jianyong Wu (Arm Technology China) wrote:
> > Hi,
> 
> Hi,
> 
> >> -----Original Message-----
> >> From: Julien Grall <julien.grall@xxxxxxx>
> >> Sent: Saturday, November 10, 2018 1:56 AM
> >> To: Jianyong Wu (Arm Technology China) <Jianyong.Wu@xxxxxxx>;
> minios-
> >> devel@xxxxxxxxxxxxxxxxxxxx; simon.kuenzer@xxxxxxxxx
> >> Cc: Kaly Xin (Arm Technology China) <Kaly.Xin@xxxxxxx>; nd
> >> <nd@xxxxxxx>; Wei Chen (Arm Technology China)
> <Wei.Chen@xxxxxxx>
> >> Subject: Re: [Minios-devel] [UNIKRAFT RFC PATCH 2/2] plat/common:
> Add
> >> a trap function to handle Arm64 irq trap
> >>
> >> Hi,
> >>
> >> On 09/11/2018 09:02, Jianyong Wu wrote:
> >>> From: Wei Chen <wei.chen@xxxxxxx>
> >>>
> >>> Change-Id: I3652599f8385fc67a29ab2d9e67861590c0f9f6c
> >>> Signed-off-by: Wei Chen <wei.chen@xxxxxxx>
> >>> ---
> >>>    plat/common/arm/traps.c   | 27 +++++++++++++++++++++++++++
> >>>    plat/kvm/arm/exceptions.S | 10 +++++++++-
> >>>    2 files changed, 36 insertions(+), 1 deletion(-)
> >>>
> >>> diff --git a/plat/common/arm/traps.c b/plat/common/arm/traps.c index
> >>> 43235be..257106b 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 +69,29 @@ 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) {
> >>> +                 gic_eoi_irq(stat);
> >>> +                 isb();
> >>> +                 _ukplat_irq_handle((unsigned long)irq);
> >>> +                 continue;
> >>> +         }
> >>
> >> Looking again at this code, could you explain why you EOI the
> >> interrupt before handling it?
> >
> > I just copy this from freebsd, but I don't know why. Do you know why bsd
> does that?
> 
> I guess you mean you copied from sys/arm/arm/gic.c? I took a look at it and
> also at sys/arm64/arm64/gic_v3.c.
> 
> FreeBSD is EOIing the interrupt early (i.e before the handler is called) only 
> for
> edge-interrupt and IPI. For level interrupt, they will be acknowledge later.
> This is because as soon as you EOI a level interrupt, it can possibly fire 
> again
> because the interrupt line is still high/low.
> 
> For simplicity, I would always EOI the interrupt after
> _ukplat_irq_handle(...) is called.

Ok, I see. I will adjust the order of eoi and handler.

Bests
Jianyong wu
> 
> Cheers,
> 
> --
> Julien Grall
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