On Wed, Jun 10, 2026 at 01:37:26PM +0530, Aneesh Kumar K.V wrote:

Jason Gunthorpe [off-list ref] writes:

quoted

On Thu, Jun 04, 2026 at 02:09:43PM +0530, Aneesh Kumar K.V (Arm) wrote:

quoted

 struct page *dma_alloc_from_pool(struct device *dev, size_t size,
-		void **cpu_addr, gfp_t gfp,
+		void **cpu_addr, gfp_t gfp, unsigned long attrs,
 		bool (*phys_addr_ok)(struct device *, phys_addr_t, size_t))
 {
-	struct gen_pool *pool = NULL;
+	struct dma_gen_pool *dma_pool = NULL;
 	struct page *page;
 	bool pool_found = false;
 
-	while ((pool = dma_guess_pool(pool, gfp))) {
+	while ((dma_pool = dma_guess_pool(dma_pool, gfp))) {
+
+		if (dma_pool->unencrypted != !!(attrs & DMA_ATTR_CC_SHARED))
+			continue;

I don't think you should be overloading DMA_ATTR_CC_SHARED like this.

	/*
	 * DMA_ATTR_CC_SHARED is not a caller-visible dma_alloc_*()
	 * attribute. The direct allocator uses it internally after it has
	 * decided that the backing pages must be shared/decrypted, so the
	 * rest of the allocation path can consistently select DMA addresses,
	 * choose compatible pools and restore encryption on free.
	 */
	if (attrs & DMA_ATTR_CC_SHARED)
		return NULL;

	if (force_dma_unencrypted(dev)) {
		attrs |= DMA_ATTR_CC_SHARED;
		mark_mem_decrypt = true;
	}

It is fine to have a bit inside the attrs that is only used by the
internal logic, but it needs to have a clearer name
__DMA_ATTR_REQUIRE_CC_SHARED perhaps.

Are you suggesting adding another attribute in addition to
DMA_ATTR_CC_SHARED?

Is the idea that __DMA_ATTR_REQUIRE_CC_SHARED would be used in the
allocation path to request a CC_SHARED allocation, while
DMA_ATTR_CC_SHARED would be used in the mapping path to describe the
attribute of the address?

Yeah, it is a thought at least

Maybe a comment is good enough.

I just find it hard to follow when we have this dual usage. Like the
code above for dma_pool->unencrypted is completely wrong if it is an
"attribute of an address". Easy to cut & paste that into the wrong
context.

Especially if you move things up higher.. having the alloc set both
CC_SHARED and REQUIRE_CC_SHARED or maybe ALLOC_CC_SHARED would make it
clearer that the alloc code lives under that callchain

Jason