Re: [PATCH kernel v4 02/19] powerpc/mm/iommu/vfio_spapr_tce: Change mm_iommu_get to reference a region

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

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On Fri, Nov 23, 2018 at 04:52:47PM +1100, Alexey Kardashevskiy wrote:
> Normally mm_iommu_get() is supposed to add a reference and
> mm_iommu_put() to remove it. However historically mm_iommu_find() does
> the referencing and mm_iommu_get() is doing allocation and referencing.
> 
> We are going to add another helper to preregister device memory so
> instead of having mm_iommu_new() which pre-registers the normal memory
> and references the region, we need separate helpers for pre-registering
> and referencing.
> 
> This renames:
> - mm_iommu_get to mm_iommu_new;
> - mm_iommu_find to mm_iommu_get.
> 
> To make the mm_iommu_get name reflect what it is supposed to do, this
> changes mm_iommu_get() to reference the region so from now on for every
> mm_iommu_get() we need a matching mm_iommu_put().
> 
> This removes the check for exact match as the check for overlap is
> enough now.
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>

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

> ---
> Changes:
> v4:
> * squashed "powerpc/mm/iommu: Make mm_iommu_new() fail on existing regions" into this
> 
> v2:
> * merged 2 patches into one
> ---
>  arch/powerpc/include/asm/mmu_context.h |  4 +--
>  arch/powerpc/mm/mmu_context_iommu.c    | 19 +++++++------
>  drivers/vfio/vfio_iommu_spapr_tce.c    | 37 +++++++++++++++++---------
>  3 files changed, 35 insertions(+), 25 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
> index 0381394..2d6b00d 100644
> --- a/arch/powerpc/include/asm/mmu_context.h
> +++ b/arch/powerpc/include/asm/mmu_context.h
> @@ -21,7 +21,7 @@ struct mm_iommu_table_group_mem_t;
>  
>  extern int isolate_lru_page(struct page *page);	/* from internal.h */
>  extern bool mm_iommu_preregistered(struct mm_struct *mm);
> -extern long mm_iommu_get(struct mm_struct *mm,
> +extern long mm_iommu_new(struct mm_struct *mm,
>  		unsigned long ua, unsigned long entries,
>  		struct mm_iommu_table_group_mem_t **pmem);
>  extern long mm_iommu_put(struct mm_struct *mm,
> @@ -32,7 +32,7 @@ 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,
> +extern struct mm_iommu_table_group_mem_t *mm_iommu_get(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 int pageshift, unsigned long *hpa);
> diff --git a/arch/powerpc/mm/mmu_context_iommu.c b/arch/powerpc/mm/mmu_context_iommu.c
> index 1d5161f..580d89e 100644
> --- a/arch/powerpc/mm/mmu_context_iommu.c
> +++ b/arch/powerpc/mm/mmu_context_iommu.c
> @@ -89,7 +89,7 @@ bool mm_iommu_preregistered(struct mm_struct *mm)
>  }
>  EXPORT_SYMBOL_GPL(mm_iommu_preregistered);
>  
> -long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
> +long mm_iommu_new(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>  		struct mm_iommu_table_group_mem_t **pmem)
>  {
>  	struct mm_iommu_table_group_mem_t *mem;
> @@ -102,12 +102,6 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>  
>  	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list,
>  			next) {
> -		if ((mem->ua == ua) && (mem->entries == entries)) {
> -			++mem->used;
> -			*pmem = mem;
> -			goto unlock_exit;
> -		}
> -
>  		/* Overlap? */
>  		if ((mem->ua < (ua + (entries << PAGE_SHIFT))) &&
>  				(ua < (mem->ua +
> @@ -202,7 +196,7 @@ long mm_iommu_get(struct mm_struct *mm, unsigned long ua, unsigned long entries,
>  
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(mm_iommu_get);
> +EXPORT_SYMBOL_GPL(mm_iommu_new);
>  
>  static void mm_iommu_unpin(struct mm_iommu_table_group_mem_t *mem)
>  {
> @@ -318,21 +312,26 @@ struct mm_iommu_table_group_mem_t *mm_iommu_lookup_rm(struct mm_struct *mm,
>  	return ret;
>  }
>  
> -struct mm_iommu_table_group_mem_t *mm_iommu_find(struct mm_struct *mm,
> +struct mm_iommu_table_group_mem_t *mm_iommu_get(struct mm_struct *mm,
>  		unsigned long ua, unsigned long entries)
>  {
>  	struct mm_iommu_table_group_mem_t *mem, *ret = NULL;
>  
> +	mutex_lock(&mem_list_mutex);
> +
>  	list_for_each_entry_rcu(mem, &mm->context.iommu_group_mem_list, next) {
>  		if ((mem->ua == ua) && (mem->entries == entries)) {
>  			ret = mem;
> +			++mem->used;
>  			break;
>  		}
>  	}
>  
> +	mutex_unlock(&mem_list_mutex);
> +
>  	return ret;
>  }
> -EXPORT_SYMBOL_GPL(mm_iommu_find);
> +EXPORT_SYMBOL_GPL(mm_iommu_get);
>  
>  long mm_iommu_ua_to_hpa(struct mm_iommu_table_group_mem_t *mem,
>  		unsigned long ua, unsigned int pageshift, unsigned long *hpa)
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index ad63725..56db071 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -151,12 +151,13 @@ static long tce_iommu_unregister_pages(struct tce_container *container,
>  {
>  	struct mm_iommu_table_group_mem_t *mem;
>  	struct tce_iommu_prereg *tcemem;
> -	bool found = false;
> +	bool found;
> +	long ret;
>  
>  	if ((vaddr & ~PAGE_MASK) || (size & ~PAGE_MASK))
>  		return -EINVAL;
>  
> -	mem = mm_iommu_find(container->mm, vaddr, size >> PAGE_SHIFT);
> +	mem = mm_iommu_get(container->mm, vaddr, size >> PAGE_SHIFT);
>  	if (!mem)
>  		return -ENOENT;
>  
> @@ -168,9 +169,13 @@ static long tce_iommu_unregister_pages(struct tce_container *container,
>  	}
>  
>  	if (!found)
> -		return -ENOENT;
> +		ret = -ENOENT;
> +	else
> +		ret = tce_iommu_prereg_free(container, tcemem);
>  
> -	return tce_iommu_prereg_free(container, tcemem);
> +	mm_iommu_put(container->mm, mem);
> +
> +	return ret;
>  }
>  
>  static long tce_iommu_register_pages(struct tce_container *container,
> @@ -185,22 +190,24 @@ static long tce_iommu_register_pages(struct tce_container *container,
>  			((vaddr + size) < vaddr))
>  		return -EINVAL;
>  
> -	mem = mm_iommu_find(container->mm, vaddr, entries);
> +	mem = mm_iommu_get(container->mm, vaddr, entries);
>  	if (mem) {
>  		list_for_each_entry(tcemem, &container->prereg_list, next) {
> -			if (tcemem->mem == mem)
> -				return -EBUSY;
> +			if (tcemem->mem == mem) {
> +				ret = -EBUSY;
> +				goto put_exit;
> +			}
>  		}
> +	} else {
> +		ret = mm_iommu_new(container->mm, vaddr, entries, &mem);
> +		if (ret)
> +			return ret;
>  	}
>  
> -	ret = mm_iommu_get(container->mm, vaddr, entries, &mem);
> -	if (ret)
> -		return ret;
> -
>  	tcemem = kzalloc(sizeof(*tcemem), GFP_KERNEL);
>  	if (!tcemem) {
> -		mm_iommu_put(container->mm, mem);
> -		return -ENOMEM;
> +		ret = -ENOMEM;
> +		goto put_exit;
>  	}
>  
>  	tcemem->mem = mem;
> @@ -209,6 +216,10 @@ static long tce_iommu_register_pages(struct tce_container *container,
>  	container->enabled = true;
>  
>  	return 0;
> +
> +put_exit:
> +	mm_iommu_put(container->mm, mem);
> +	return ret;
>  }
>  
>  static bool tce_page_is_contained(struct page *page, unsigned page_shift)

-- 
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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