Re: [Patch v1] x86: Fix the logical destination mode test

[Marcelo Tosatti <mtosatti@redhat.com>]

On Mon, Mar 09, 2020 at 07:15:50PM -0400, Nitesh Narayan Lal wrote:
> There are following issues with the ioapic logical destination mode test:
> 
> - A race condition that is triggered when the interrupt handler
>   ioapic_isr_86() is called at the same time by multiple vCPUs. Due to this
>   the g_isr_86 is not correctly incremented. To prevent this a spinlock is
>   added around ‘g_isr_86++’.
> 
> - On older QEMU versions initial x2APIC ID is not set, that is why
>   the local APIC IDs of each vCPUs are not configured. Hence the logical
>   destination mode test fails/hangs. Adding ‘+x2apic’ to the qemu -cpu params
>   ensures that the local APICs are configured every time, irrespective of the
>   QEMU version.
> 
> - With ‘-machine kernel_irqchip=split’ included in the ioapic test
>   test_ioapic_self_reconfigure() always fails and somehow leads to a state where
>   after submitting IOAPIC fixed delivery - logical destination mode request we
>   never receive an interrupt back. For now, the physical and logical destination
>   mode tests are moved above test_ioapic_self_reconfigure().
> 
> Fixes: b2a1ee7e ("kvm-unit-test: x86: ioapic: Test physical and logical destination mode")
> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>

Looks good to me.

> ---
>  x86/ioapic.c      | 11 +++++++----
>  x86/unittests.cfg |  2 +-
>  2 files changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/x86/ioapic.c b/x86/ioapic.c
> index 742c711..3106531 100644
> --- a/x86/ioapic.c
> +++ b/x86/ioapic.c
> @@ -432,10 +432,13 @@ static void test_ioapic_physical_destination_mode(void)
>  }
>  
>  static volatile int g_isr_86;
> +struct spinlock ioapic_lock;
>  
>  static void ioapic_isr_86(isr_regs_t *regs)
>  {
> +	spin_lock(&ioapic_lock);
>  	++g_isr_86;
> +	spin_unlock(&ioapic_lock);
>  	set_irq_line(0x0e, 0);
>  	eoi();
>  }
> @@ -501,6 +504,10 @@ int main(void)
>  	test_ioapic_level_tmr(true);
>  	test_ioapic_edge_tmr(true);
>  
> +	test_ioapic_physical_destination_mode();
> +	if (cpu_count() > 3)
> +		test_ioapic_logical_destination_mode();
> +
>  	if (cpu_count() > 1) {
>  		test_ioapic_edge_tmr_smp(false);
>  		test_ioapic_level_tmr_smp(false);
> @@ -508,11 +515,7 @@ int main(void)
>  		test_ioapic_edge_tmr_smp(true);
>  
>  		test_ioapic_self_reconfigure();
> -		test_ioapic_physical_destination_mode();
>  	}
>  
> -	if (cpu_count() > 3)
> -		test_ioapic_logical_destination_mode();
> -
>  	return report_summary();
>  }
> diff --git a/x86/unittests.cfg b/x86/unittests.cfg
> index f2401eb..d658bc8 100644
> --- a/x86/unittests.cfg
> +++ b/x86/unittests.cfg
> @@ -46,7 +46,7 @@ timeout = 30
>  [ioapic]
>  file = ioapic.flat
>  smp = 4
> -extra_params = -cpu qemu64
> +extra_params = -cpu qemu64,+x2apic
>  arch = x86_64
>  
>  [cmpxchg8b]
> -- 
> 1.8.3.1