Re: [PATCH kernel 4/9] powerpc/mmu: Add real mode support for IOMMU preregistered memory

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Dec 08, 2016 at 07:19:51PM +1100, Alexey Kardashevskiy wrote:
> This makes mm_iommu_lookup() able to work in realmode by replacing
> list_for_each_entry_rcu() (which can do debug stuff which can fail in
> real mode) with list_for_each_entry_lockless().
> 
> This adds realmode version of mm_iommu_ua_to_hpa() which adds
> explicit vmalloc'd-to-linear address conversion.
> Unlike mm_iommu_ua_to_hpa(), mm_iommu_ua_to_hpa_rm() can fail.
> 
> This changes mm_iommu_preregistered() to receive @mm as in real mode
> @current does not always have a correct pointer.
> 
> This adds realmode version of mm_iommu_lookup() which receives @mm
> (for the same reason as for mm_iommu_preregistered()) and uses
> lockless version of list_for_each_entry_rcu().
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  arch/powerpc/include/asm/mmu_context.h |  4 ++++
>  arch/powerpc/mm/mmu_context_iommu.c    | 39 ++++++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
> index b9e3f0aca261..c70c8272523d 100644
> --- a/arch/powerpc/include/asm/mmu_context.h
> +++ b/arch/powerpc/include/asm/mmu_context.h
> @@ -29,10 +29,14 @@ extern void mm_iommu_init(struct mm_struct *mm);
>  extern void mm_iommu_cleanup(struct mm_struct *mm);
>  extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
>  		unsigned long ua, unsigned long size);
> +extern struct mm_iommu_table_group_mem_t *mm_iommu_lookup_rm(
> +		struct mm_struct *mm, unsigned long ua, unsigned long size);
>  extern struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
>  		unsigned long ua, unsigned long entries);
>  extern long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
>  		unsigned long ua, unsigned long *hpa);
> +extern long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem,
> +		unsigned long ua, unsigned long *hpa);
>  extern long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem);
>  extern void mm_iommu_mapped_dec(struct mm_iommu_table_group_mem_t *mem);
>  #endif
> diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
> index 104bad029ce9..631d32f5937b 100644
> --- a/arch/powerpc/mm/mmu_context_iommu.c
> +++ b/arch/powerpc/mm/mmu_context_iommu.c
> @@ -314,6 +314,25 @@ struct mm_iommu_table_group_mem_t *mm_iommu_lookup(struct mm_struct *mm,
>  }
>  EXPORT_SYMBOL_GPL(mm_iommu_lookup);
>  
> +struct mm_iommu_table_group_mem_t *mm_iommu_lookup_rm(struct mm_struct *mm,
> +		unsigned long ua, unsigned long size)
> +{
> +	struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
> +
> +	list_for_each_entry_lockless(mem, &mm->context.iommu_group_mem_list,
> +			next) {
> +		if ((mem->ua <= ua) &&
> +				(ua + size <= mem->ua +
> +				 (mem->entries << PAGE_SHIFT))) {
> +			ret = mem;
> +			break;
> +		}
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(mm_iommu_lookup_rm);
> +
>  struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
>  		unsigned long ua, unsigned long entries)
>  {
> @@ -345,6 +364,26 @@ long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
>  }
>  EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa);
>  
> +long mm_iommu_ua_to_hpa_rm(struct mm_iommu_table_group_mem_t *mem,
> +		unsigned long ua, unsigned long *hpa)
> +{
> +	const long entry = (ua - mem->ua) >> PAGE_SHIFT;
> +	void *va = &mem->hpas[entry];
> +	unsigned long *pa;
> +
> +	if (entry >= mem->entries)
> +		return -EFAULT;
> +
> +	pa = (void *) vmalloc_to_phys(va);
> +	if (!pa)
> +		return -EFAULT;
> +
> +	*hpa = *pa | (ua & ~PAGE_MASK);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(mm_iommu_ua_to_hpa_rm);
> +
>  long mm_iommu_mapped_inc(struct mm_iommu_table_group_mem_t *mem)
>  {
>  	if (atomic64_inc_not_zero(&mem->mapped))

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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