Re: [PATCH v7 07/15] iommu: Hook up '->unmap_pages' driver callback

[Lu Baolu]

On 6/16/21 9:38 PM, Georgi Djakov wrote:
> From: Will Deacon <will@xxxxxxxxxx>
>
> Extend iommu_pgsize() to populate an optional 'count' parameter so that
> we can direct unmapping operation to the ->unmap_pages callback if it
> has been provided by the driver.
>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> Signed-off-by: Isaac J. Manjarres <isaacm@xxxxxxxxxxxxxx>
> Signed-off-by: Georgi Djakov <quic_c_gdjako@xxxxxxxxxxx>
> ---
>   drivers/iommu/iommu.c | 59 +++++++++++++++++++++++++++++++++++++++++++--------
>   1 file changed, 50 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 80e14c139d40..725622c7e603 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2376,11 +2376,11 @@ phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain, dma_addr_t iova)
>   EXPORT_SYMBOL_GPL(iommu_iova_to_phys);
>   
>   static size_t iommu_pgsize(struct iommu_domain *domain, unsigned long iova,
> -			   phys_addr_t paddr, size_t size)
> +			   phys_addr_t paddr, size_t size, size_t *count)
>   {
> -	unsigned int pgsize_idx;
> +	unsigned int pgsize_idx, pgsize_idx_next;
>   	unsigned long pgsizes;
> -	size_t pgsize;
> +	size_t offset, pgsize, pgsize_next;
>   	unsigned long addr_merge = paddr | iova;
>   
>   	/* Page sizes supported by the hardware and small enough for @size */
> @@ -2396,7 +2396,36 @@ static size_t iommu_pgsize(struct iommu_domain *domain, unsigned long iova,
>   	/* Pick the biggest page size remaining */
>   	pgsize_idx = __fls(pgsizes);
>   	pgsize = BIT(pgsize_idx);
> +	if (!count)
> +		return pgsize;
>   
> +	/* Find the next biggest support page size, if it exists */
> +	pgsizes = domain->pgsize_bitmap & ~GENMASK(pgsize_idx, 0);
> +	if (!pgsizes)
> +		goto out_set_count;
> +
> +	pgsize_idx_next = __ffs(pgsizes);
> +	pgsize_next = BIT(pgsize_idx_next);
> +
> +	/*
> +	 * There's no point trying a bigger page size unless the virtual
> +	 * and physical addresses are similarly offset within the larger page.
> +	 */
> +	if ((iova ^ paddr) & (pgsize_next - 1))
> +		goto out_set_count;
> +
> +	/* Calculate the offset to the next page size alignment boundary */
> +	offset = pgsize_next - (addr_merge & (pgsize_next - 1));
> +
> +	/*
> +	 * If size is big enough to accommodate the larger page, reduce
> +	 * the number of smaller pages.
> +	 */
> +	if (offset + pgsize_next <= size)
> +		size = offset;
> +
> +out_set_count:
> +	*count = size >> pgsize_idx;
>   	return pgsize;
>   }
>   
> @@ -2434,7 +2463,7 @@ static int __iommu_map(struct iommu_domain *domain, unsigned long iova,
>   	pr_debug("map: iova 0x%lx pa %pa size 0x%zx\n", iova, &paddr, size);
>   
>   	while (size) {
> -		size_t pgsize = iommu_pgsize(domain, iova, paddr, size);
> +		size_t pgsize = iommu_pgsize(domain, iova, paddr, size, NULL);
>   
>   		pr_debug("mapping: iova 0x%lx pa %pa pgsize 0x%zx\n",
>   			 iova, &paddr, pgsize);
> @@ -2485,6 +2514,19 @@ int iommu_map_atomic(struct iommu_domain *domain, unsigned long iova,
>   }
>   EXPORT_SYMBOL_GPL(iommu_map_atomic);
>   
> +static size_t __iommu_unmap_pages(struct iommu_domain *domain,
> +				  unsigned long iova, size_t size,
> +				  struct iommu_iotlb_gather *iotlb_gather)
> +{
> +	const struct iommu_ops *ops = domain->ops;
> +	size_t pgsize, count;
> +
> +	pgsize = iommu_pgsize(domain, iova, iova, size, &count);
> +	return ops->unmap_pages ?
> +	       ops->unmap_pages(domain, iova, pgsize, count, iotlb_gather) :
> +	       ops->unmap(domain, iova, pgsize, iotlb_gather);
> +}
> +
>   static size_t __iommu_unmap(struct iommu_domain *domain,
>   			    unsigned long iova, size_t size,
>   			    struct iommu_iotlb_gather *iotlb_gather)
> @@ -2494,7 +2536,7 @@ static size_t __iommu_unmap(struct iommu_domain *domain,
>   	unsigned long orig_iova = iova;
>   	unsigned int min_pagesz;
>   
> -	if (unlikely(ops->unmap == NULL ||
> +	if (unlikely(!(ops->unmap || ops->unmap_pages) ||
>   		     domain->pgsize_bitmap == 0UL))
>   		return 0;
>   
> @@ -2522,10 +2564,9 @@ static size_t __iommu_unmap(struct iommu_domain *domain,
>   	 * or we hit an area that isn't mapped.
>   	 */
>   	while (unmapped < size) {
> -		size_t pgsize;
> -
> -		pgsize = iommu_pgsize(domain, iova, iova, size - unmapped);
> -		unmapped_page = ops->unmap(domain, iova, pgsize, iotlb_gather);
> +		unmapped_page = __iommu_unmap_pages(domain, iova,
> +						    size - unmapped,
> +						    iotlb_gather);
>   		if (!unmapped_page)
>   			break;
>   

Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>

Best regards,
baolu