Jason Gunthorpe <[email protected]> writes:
> On Thu, Jun 04, 2026 at 02:09:43PM +0530, Aneesh Kumar K.V (Arm) wrote:
>> 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?
>
> The sashiko note does look legit though:
>
> if (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
> !gfpflags_allow_blocking(gfp) && !coherent) {
> page = dma_alloc_from_pool(dev, PAGE_ALIGN(size), &cpu_addr,
> gfp, attrs, NULL);
> if (!page)
> return NULL;
>
> I don't see anything doing the force_dma_unencrypted test along this
> callchain..
>
> I guess it should be done one step up in dma_alloc_attrs() instead of
> in dma_direct_alloc()?
>
Yes, I'll move it there.
-aneesh
