Re: [PATCH v2] iommu/dma: simplify dma_iova_destroy() and drop the free_iova helper

["Huang, Honglei" <honghuan@amd.com>]

On 7/13/2026 3:33 PM, Marek Szyprowski wrote:
> On 03.07.2026 05:37, Honglei Huang wrote:
>> dma_iova_destroy() frees the IOVA space through __iommu_dma_iova_unlink()
>> using a "free_iova" boolean, which duplicates the IOVA free logic in
>> dma_iova_free(). And it frees using the unmapped @mapped_len, which for a
>> partially linked reservation is smaller than the reserved size. This
>> results in a benign waste as pointed out by Robin, not a leak. So this is
>> a cleanup, not a fix.
>>
>> Drop the duplicated free path. Fold __iommu_dma_iova_unlink into
>> dma_iova_unlink and remove the free_iova parameter so it only unmaps.
>> dma_iova_destroy then unlinks the mapped range if mapped_len is set and
>> unconditionally calls dma_iova_free, which frees the whole reservation
>> via dma_iova_size. The freed size now always matches the reserved size,
>> and destroy reads as unlink then free.
>>
>> Note that dma_iova_destroy() no longer routes the free through the flush
>> queue; teardown now unmaps synchronously and frees directly, matching
>> dma_iova_free().
>>
>> No functional change intended for callers.
>>
>> Suggested-by: Leon Romanovsky <leonro@nvidia.com>
>> Signed-off-by: Honglei Huang <honghuan@amd.com>
> 
> 
> Applied to dma-mapping-for-next. Thanks!

Thanks for the merging!

Regards,
Honglei

> 
> 
>> ---
>> Changes since v1:
>>   - Reframed from an IOVA-leak fix into a cleanup; dropped Fixes:/Cc: stable.
>>   - Fold the free_iova helper into dma_iova_unlink() according to Leon's
>>     diff, so destroy is unlink + dma_iova_free(). Added Suggested-by: Leon.
>>
>>   drivers/iommu/dma-iommu.c | 57 +++++++++++++++------------------------
>>   1 file changed, 22 insertions(+), 35 deletions(-)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index 9abaec0703e..5598ed4bff7 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -2068,10 +2068,20 @@ static void iommu_dma_iova_unlink_range_slow(struct device *dev,
>>   		arch_sync_dma_flush();
>>   }
>>   
>> -static void __iommu_dma_iova_unlink(struct device *dev,
>> -		struct dma_iova_state *state, size_t offset, size_t size,
>> -		enum dma_data_direction dir, unsigned long attrs,
>> -		bool free_iova)
>> +/**
>> + * dma_iova_unlink - Unlink a range of IOVA space
>> + * @dev: DMA device
>> + * @state: IOVA state
>> + * @offset: offset into the IOVA state to unlink
>> + * @size: size of the buffer
>> + * @dir: DMA direction
>> + * @attrs: attributes of mapping properties
>> + *
>> + * Unlink a range of IOVA space for the given IOVA state.
>> + */
>> +void dma_iova_unlink(struct device *dev, struct dma_iova_state *state,
>> +		size_t offset, size_t size, enum dma_data_direction dir,
>> +		unsigned long attrs)
>>   {
>>   	struct iommu_domain *domain = iommu_get_dma_domain(dev);
>>   	struct iommu_dma_cookie *cookie = domain->iova_cookie;
>> @@ -2087,35 +2097,13 @@ static void __iommu_dma_iova_unlink(struct device *dev,
>>   		iommu_dma_iova_unlink_range_slow(dev, addr, size, dir, attrs);
>>   
>>   	iommu_iotlb_gather_init(&iotlb_gather);
>> -	iotlb_gather.queued = free_iova && READ_ONCE(cookie->fq_domain);
>>   
>>   	size = iova_align(iovad, size + iova_start_pad);
>>   	addr -= iova_start_pad;
>>   	unmapped = iommu_unmap_fast(domain, addr, size, &iotlb_gather);
>>   	WARN_ON(unmapped != size);
>>   
>> -	if (!iotlb_gather.queued)
>> -		iommu_iotlb_sync(domain, &iotlb_gather);
>> -	if (free_iova)
>> -		iommu_dma_free_iova(domain, addr, size, &iotlb_gather);
>> -}
>> -
>> -/**
>> - * dma_iova_unlink - Unlink a range of IOVA space
>> - * @dev: DMA device
>> - * @state: IOVA state
>> - * @offset: offset into the IOVA state to unlink
>> - * @size: size of the buffer
>> - * @dir: DMA direction
>> - * @attrs: attributes of mapping properties
>> - *
>> - * Unlink a range of IOVA space for the given IOVA state.
>> - */
>> -void dma_iova_unlink(struct device *dev, struct dma_iova_state *state,
>> -		size_t offset, size_t size, enum dma_data_direction dir,
>> -		unsigned long attrs)
>> -{
>> -	 __iommu_dma_iova_unlink(dev, state, offset, size, dir, attrs, false);
>> +	iommu_iotlb_sync(domain, &iotlb_gather);
>>   }
>>   EXPORT_SYMBOL_GPL(dma_iova_unlink);
>>   
>> @@ -2136,14 +2124,13 @@ void dma_iova_destroy(struct device *dev, struct dma_iova_state *state,
>>   		unsigned long attrs)
>>   {
>>   	if (mapped_len)
>> -		__iommu_dma_iova_unlink(dev, state, 0, mapped_len, dir, attrs,
>> -				true);
>> -	else
>> -		/*
>> -		 * We can be here if first call to dma_iova_link() failed and
>> -		 * there is nothing to unlink, so let's be more clear.
>> -		 */
>> -		dma_iova_free(dev, state);
>> +		dma_iova_unlink(dev, state, 0, mapped_len, dir, attrs);
>> +
>> +	/*
>> +	 * We can be here if the first call to dma_iova_link() failed and
>> +	 * there is nothing to unlink, so let's be more clear.
>> +	 */
>> +	dma_iova_free(dev, state);
>>   }
>>   EXPORT_SYMBOL_GPL(dma_iova_destroy);
>>   
>>
>> base-commit: dc59e4fea9d83f03bad6bddf3fa2e52491777482
> 
> Best regards