[PATCH] iommu/amd: Fix schedule-while-atomic BUG in initialization code

[Joerg Roedel]

Hi Artem, Thomas,

On Wed, Jul 26, 2017 at 12:42:49PM +0200, Thomas Gleixner wrote:
> On Tue, 25 Jul 2017, Artem Savkov wrote:
> 
> > Hi,
> > 
> > Commit 1c3c5ea "sched/core: Enable might_sleep() and smp_processor_id()
> > checks early" seem to have uncovered an issue with amd-iommu/x2apic.
> > 
> > Starting with that commit the following warning started to show up on AMD
> > systems during boot:
>  
> > [    0.160000] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:747 
> 
> > [    0.160000]  mutex_lock_nested+0x1b/0x20 
> > [    0.160000]  register_syscore_ops+0x1d/0x70 
> > [    0.160000]  state_next+0x119/0x910 
> > [    0.160000]  iommu_go_to_state+0x29/0x30 
> > [    0.160000]  amd_iommu_enable+0x13/0x23 
> > [    0.160000]  irq_remapping_enable+0x1b/0x39 
> > [    0.160000]  enable_IR_x2apic+0x91/0x196 
> > [    0.160000]  default_setup_apic_routing+0x16/0x6e 
> > [    0.160000]  native_smp_prepare_cpus+0x257/0x2d5

Thanks for the report!

> --- a/drivers/iommu/amd_iommu_init.c
> +++ b/drivers/iommu/amd_iommu_init.c
> @@ -2440,7 +2440,6 @@ static int __init state_next(void)
>  		break;
>  	case IOMMU_ACPI_FINISHED:
>  		early_enable_iommus();
> -		register_syscore_ops(&amd_iommu_syscore_ops);
>  		x86_platform.iommu_shutdown = disable_iommus;
>  		init_state = IOMMU_ENABLED;
>  		break;
> @@ -2559,6 +2558,8 @@ static int __init amd_iommu_init(void)
>  			for_each_iommu(iommu)
>  				iommu_flush_all_caches(iommu);
>  		}
> +	} else {
> +		register_syscore_ops(&amd_iommu_syscore_ops);
>  	}
>  
>  	return ret;

Yes, that should fix it, but I think its better to just move the
register_syscore_ops() call to a later initialization step, like in the
patch below. I tested it an will queue it to my iommu/fixes branch.