Re: [RFC PATCH] xen/arm: Introduce GICV3 Self Tests

[Grygorii Strashko <grygorii_strashko@xxxxxxxx>]

Hi Ayan,

On 22.09.25 19:55, Ayan Kumar Halder wrote:
> On 16/09/2025 11:55, Grygorii Strashko wrote:
> > Hi Ayan,
> Hi Grygorii,
> > On 12.09.25 20:00, Ayan Kumar Halder wrote:
> > > Introduce CONFIG_GICV3_SELFTEST to enclose tests for GICv3 driver.
> > > Test that Xen is able to generate SGIs.
> > >
> > > Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> > > ---
> > > One of the aim of functional safety is to test hw/sw interface. This means that
> > > Xen is able to configure the hardware correctly for the desired functionalities.
> > >
> > > Normally this is tested from the VMs. For eg if a VM is able to receive irq, 
> > > this
> > > implies that Xen has configured the GICv3 interface 'correctly'. However this is
> > > a high level (or integration) test which uses not only the GICv3 interface
> > > between Xen and VM, but the interrupt injection code for Xen to VMs.
> > >
> > > We want to have some kind of unit tests to check that Xen is able to receive
> > > various interrupts, set priorities, etc. Here, we have written unit tests for
> > > software generated interrupts (SGIs) as example.
> > >
> > > These tests are expected to be triggered as Xen boots (right after Xen has
> > > initialised the GICv3 interface ie gicv3_init(). The aim of this test is to
> > > check whether Xen can trigger SGIs after gicv3_init() is invoked. If so, we can
> > > claim that gicv3_init() was done properly to be able to trigger SGIs. Likewise
> > > we will have tests to check for priorities, SPIs, etc.
> > >
> > > A script will parse the logs and claim that Xen is able to trigger SGIs.
> > >
> > >   xen/arch/arm/Kconfig  |  8 ++++++++
> > >   xen/arch/arm/gic-v3.c |  7 +++++++
> > >   xen/arch/arm/gic.c    | 21 +++++++++++++++++++++
> > >   3 files changed, 36 insertions(+)
> > >
> > > diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> > > index 950e4452c1..739f99eaa9 100644
> > > --- a/xen/arch/arm/Kconfig
> > > +++ b/xen/arch/arm/Kconfig
> > > @@ -73,6 +73,14 @@ config GICV3
> > >         Driver for the ARM Generic Interrupt Controller v3.
> > >         If unsure, use the default setting.
> > >   +config GICV3_SELFTEST
> > > +    bool "GICv3 driver self test"
> > > +    default n
> > > +    depends on GICV3
> > > +    ---help---
> > > +
> > > +      Self tests to validate GICV3 driver.
> > > +
> > >   config HAS_ITS
> > >           bool "GICv3 ITS MSI controller support (UNSUPPORTED)" if UNSUPPORTED
> > >           depends on GICV3 && !NEW_VGIC && !ARM_32
> > > diff --git a/xen/arch/arm/gic-v3.c b/xen/arch/arm/gic-v3.c
> > > index 4e6c98bada..eb0c05231c 100644
> > > --- a/xen/arch/arm/gic-v3.c
> > > +++ b/xen/arch/arm/gic-v3.c
> > > @@ -1818,6 +1818,13 @@ static int __init gicv3_init(void)
> > >         gicv3_hyp_init();
> > >   +#ifdef CONFIG_GICV3_SELFTEST
> > > +    send_SGI_self(GIC_SGI_EVENT_CHECK);
> > > +    send_SGI_self(GIC_SGI_DUMP_STATE);
> > > +    send_SGI_self(GIC_SGI_CALL_FUNCTION);
> > > +    send_SGI_self(GIC_SGI_MAX);
> > > +#endif
> > > +
> > I'd like to ask, if possible, to minimize mixing selftest and functional code.
> > Like add gic-v3-selftest.c.
> I can try that. However, the self test needs to be invoked from functional code.
>
> Also, your suggestion gave me an idea. I can do :-
>
> +static bool __initdata opt_gicv3_selftest = false;
> +
> +#ifdef CONFIG_GICV3_SELFTEST
> +opt_gicv3_selftest = true;
> +#endif
I'd like to propose to consider other approach according to the following 
assumptions:
1) the goal is "Test that Xen is able to generate SGIs.". According to the goal 
and your code
- for this test, it doesn't matter which one (SGI) is tested. Any way you don't 
call real handlers for
 GIC_SGI_x.

2) there are 16 SGIs available, only 3 are statistically defined (enum gic_sgi) 
and
It's possible to reserve one more for testing purposes,
like GIC_SGI_SELFTEST

Then, gic SGI selftest might work without breaking Xen boot (probably for gicv2 
also)

gic.c:
  do_static_sgi()
  {
   ...
   #ifdef CONFIG_GIC_SELFTEST
        case GIC_SGI_SELFTEST:
          gic_sgi_selftest();
        break;
   #endif

git-selftest.c

  gic_sgi_selftest()
  {
    // process test SGI, like count number of triggers
  }

  void [__init __constructor?] test_gic_sgi_selftest()
  {
        setup test 1
        send_SGI_self(GIC_SGI_SELFTEST)
        setup test 2
        send_SGI_allbutself(GIC_SGI_SELFTEST)
        setup test 2
        send_SGI_mask(cpu_mask, GIC_SGI_SELFTEST)
  }




> > >   out:
> > >       spin_unlock(&gicv3.lock);
> > >   diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> > > index d922ea67aa..5cb58cdb92 100644
> > > --- a/xen/arch/arm/gic.c
> > > +++ b/xen/arch/arm/gic.c
> > > @@ -346,6 +346,26 @@ static void do_sgi(struct cpu_user_regs *regs, enum 
> > > gic_sgi sgi)
> > >        */
> > >       smp_rmb();
> > >   +#ifdef CONFIG_GICV3_SELFTEST
> > if (gic_selftest_run)
> And then instead of ifdef, I can enclose the below under "if (gicv3_selftest)" .
> > > +    switch (sgi)
> > > +    {
> > > +    case GIC_SGI_EVENT_CHECK:
> > > +        printk("GIC_SGI_EVENT_CHECK received\n");
> > > +        break;
> > > +    case GIC_SGI_DUMP_STATE:
> > > +        printk("GIC_SGI_DUMP_STATE received\n");
> > > +        break;
> > > +    case GIC_SGI_CALL_FUNCTION:
> > > +        printk("GIC_SGI_CALL_FUNCTION received\n");
> > > +        break;
> > > +    case GIC_SGI_MAX:
> > > +        printk("GIC_SGI_MAX received\n");
> >        gic_selftest_done = true;
> >
> > > +        break;
> > > +    default:
> > > +        panic("Unknown SGI triggered\n");
> > > +        break;
> > > +    }
> > Potentially GIC selftest code can be guarded by some "gic_selftest_run/done" 
> > vars
> > if xen boot is expected to proceed further after testing.
> Ah no, Xen will terminate after running the self test.
>
> - Ayan
--
Best regards,
-grygorii