Re: [PATCH 18/19] iommu: Update various drivers to pass in lg2sz instead of order to iommu pages

[Robin Murphy <robin.murphy@arm.com>]

On 2025-02-04 6:34 pm, Jason Gunthorpe wrote:
> Convert most of the places calling get_order() as an argument to the
> iommu-pages allocator into order_base_2() or the _sz flavour
> instead. These places already have an exact size, there is no particular
> reason to use order here.
> 
> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
[...]
> @@ -826,7 +825,7 @@ void *__init iommu_alloc_4k_pages(struct amd_iommu *iommu, gfp_t gfp,
>   				  size_t size)
>   {
>   	int order = get_order(size);
> -	void *buf = iommu_alloc_pages(gfp, order);
> +	void *buf = iommu_alloc_pages_lg2(gfp, order + PAGE_SHIFT);

This is a size, really - it's right there above.

(although alloc_cwwb_sem() passing 1 looks highly suspicious - judging 
by other cmd_sem references that probably should be PAGE_SIZE...)

Furthermore even the set_memory_4k() call doesn't really want an order 
either, PAGE_ALIGN(size) >> PAGE_SHIFT would do.

>   
>   	if (buf &&
>   	    check_feature(FEATURE_SNP) &&
[...]
> @@ -1702,8 +1701,10 @@ int dmar_enable_qi(struct intel_iommu *iommu)
>   	 * Need two pages to accommodate 256 descriptors of 256 bits each
>   	 * if the remapping hardware supports scalable mode translation.
>   	 */
> -	order = ecap_smts(iommu->ecap) ? 1 : 0;
> -	desc = iommu_alloc_pages_node(iommu->node, GFP_ATOMIC, order);
> +	desc = iommu_alloc_pages_node_lg2(iommu->node, GFP_ATOMIC,
> +					  ecap_smts(iommu->ecap) ?
> +						  order_base_2(SZ_8K) :
> +						  order_base_2(SZ_4K));

These are also clearly sizes.

>   	if (!desc) {
>   		kfree(qi);
>   		iommu->qi = NULL;
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 8727d8e1e02f45..0e1dd519c3b9b3 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -263,14 +263,14 @@ static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
>   				    void *cookie)
>   {
>   	struct device *dev = cfg->iommu_dev;
> -	int order = get_order(size);
>   	dma_addr_t dma;
>   	void *pages;
>   
>   	if (cfg->alloc)
>   		pages = cfg->alloc(cookie, size, gfp);
>   	else
> -		pages = iommu_alloc_pages_node(dev_to_node(dev), gfp, order);
> +		pages = iommu_alloc_pages_node_lg2(dev_to_node(dev), gfp,
> +						   order_base_2(size));

Another size. Same thing in patch #17 too. I don't see any need to have 
the log2 stuff at all, I think we just switch iommu_alloc_pages{_node}() 
to take a size and keep things simple.

Thanks,
Robin.

>   
>   	if (!pages)
>   		return NULL;
> diff --git a/drivers/iommu/io-pgtable-dart.c b/drivers/iommu/io-pgtable-dart.c
> index a4cbd8a8a2976e..3b57d14baa9c1d 100644
> --- a/drivers/iommu/io-pgtable-dart.c
> +++ b/drivers/iommu/io-pgtable-dart.c
> @@ -107,13 +107,6 @@ static phys_addr_t iopte_to_paddr(dart_iopte pte,
>   	return paddr;
>   }
>   
> -static void *__dart_alloc_pages(size_t size, gfp_t gfp)
> -{
> -	int order = get_order(size);
> -
> -	return iommu_alloc_pages(gfp, order);
> -}
> -
>   static int dart_init_pte(struct dart_io_pgtable *data,
>   			     unsigned long iova, phys_addr_t paddr,
>   			     dart_iopte prot, int num_entries,
> @@ -255,7 +248,7 @@ static int dart_map_pages(struct io_pgtable_ops *ops, unsigned long iova,
>   
>   	/* no L2 table present */
>   	if (!pte) {
> -		cptep = __dart_alloc_pages(tblsz, gfp);
> +		cptep = iommu_alloc_pages_sz(gfp, tblsz);
>   		if (!cptep)
>   			return -ENOMEM;
>   
> @@ -412,7 +405,8 @@ apple_dart_alloc_pgtable(struct io_pgtable_cfg *cfg, void *cookie)
>   	cfg->apple_dart_cfg.n_ttbrs = 1 << data->tbl_bits;
>   
>   	for (i = 0; i < cfg->apple_dart_cfg.n_ttbrs; ++i) {
> -		data->pgd[i] = __dart_alloc_pages(DART_GRANULE(data), GFP_KERNEL);
> +		data->pgd[i] =
> +			iommu_alloc_pages_sz(GFP_KERNEL, DART_GRANULE(data));
>   		if (!data->pgd[i])
>   			goto out_free_data;
>   		cfg->apple_dart_cfg.ttbr[i] = virt_to_phys(data->pgd[i]);
> diff --git a/drivers/iommu/sun50i-iommu.c b/drivers/iommu/sun50i-iommu.c
> index 3d77aed8507373..d0e515bf5dd1f6 100644
> --- a/drivers/iommu/sun50i-iommu.c
> +++ b/drivers/iommu/sun50i-iommu.c
> @@ -690,8 +690,8 @@ sun50i_iommu_domain_alloc_paging(struct device *dev)
>   	if (!sun50i_domain)
>   		return NULL;
>   
> -	sun50i_domain->dt = iommu_alloc_pages(GFP_KERNEL | GFP_DMA32,
> -					      get_order(DT_SIZE));
> +	sun50i_domain->dt =
> +		iommu_alloc_pages_sz(GFP_KERNEL | GFP_DMA32, DT_SIZE);
>   	if (!sun50i_domain->dt)
>   		goto err_free_domain;
>   


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