Mostafa Saleh <[email protected]> writes:
> On Tue, May 12, 2026 at 02:33:57PM +0530, Aneesh Kumar K.V (Arm) wrote:
>> Propagate force_dma_unencrypted() into DMA_ATTR_CC_SHARED in the
>> dma-direct allocation path and use the attribute to drive the related
>> decisions.
>>
>> This updates dma_direct_alloc(), dma_direct_free(), and
>> dma_direct_alloc_pages() to fold the forced unencrypted case into attrs.
>>
>> Signed-off-by: Aneesh Kumar K.V (Arm) <[email protected]>
>> ---
>> kernel/dma/direct.c | 44 ++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 36 insertions(+), 8 deletions(-)
>>
>> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
>> index b958f150718a..0c2e1f8436ce 100644
>> --- a/kernel/dma/direct.c
>> +++ b/kernel/dma/direct.c
>> @@ -201,16 +201,31 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>> dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
>> {
>> bool remap = false, set_uncached = false;
>> - bool mark_mem_decrypt = true;
>> + bool mark_mem_decrypt = false;
>> struct page *page;
>> void *ret;
>>
>> + /*
>> + * 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;
>> + }
>> +
>> size = PAGE_ALIGN(size);
>> if (attrs & DMA_ATTR_NO_WARN)
>> gfp |= __GFP_NOWARN;
>>
>> - if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
>> - !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev))
>> + if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_CC_SHARED)) ==
>> + DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev))
>> return dma_direct_alloc_no_mapping(dev, size, dma_handle, gfp);
>>
>> if (!dev_is_dma_coherent(dev)) {
>> @@ -244,7 +259,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>> * Remapping or decrypting memory may block, allocate the memory from
>> * the atomic pools instead if we aren't allowed block.
>> */
>> - if ((remap || force_dma_unencrypted(dev)) &&
>> + if ((remap || (attrs & DMA_ATTR_CC_SHARED)) &&
>> dma_direct_use_pool(dev, gfp))
>> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
>>
>> @@ -318,11 +333,20 @@ void *dma_direct_alloc(struct device *dev, size_t size,
>> void dma_direct_free(struct device *dev, size_t size,
>> void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
>> {
>> - bool mark_mem_encrypted = true;
>> + bool mark_mem_encrypted = false;
>> unsigned int page_order = get_order(size);
>>
>> - if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
>> - !force_dma_unencrypted(dev) && !is_swiotlb_for_alloc(dev)) {
>> + /*
>> + * if the device had requested for an unencrypted buffer,
>> + * convert it to encrypted on free
>> + */
>> + if (force_dma_unencrypted(dev)) {
>> + attrs |= DMA_ATTR_CC_SHARED;
>> + mark_mem_encrypted = true;
>> + }
>> +
>> + if (((attrs & (DMA_ATTR_NO_KERNEL_MAPPING | DMA_ATTR_CC_SHARED)) ==
>> + DMA_ATTR_NO_KERNEL_MAPPING) && !is_swiotlb_for_alloc(dev)) {
>> /* cpu_addr is a struct page cookie, not a kernel address */
>> dma_free_contiguous(dev, cpu_addr, size);
>> return;
>> @@ -365,10 +389,14 @@ void dma_direct_free(struct device *dev, size_t size,
>> struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
>> dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp)
>> {
>> + unsigned long attrs = 0;
>> struct page *page;
>> void *ret;
>>
>> - if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
>> + if (force_dma_unencrypted(dev))
>> + attrs |= DMA_ATTR_CC_SHARED;
>> +
>> + if ((attrs & DMA_ATTR_CC_SHARED) && dma_direct_use_pool(dev, gfp))
>> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
>
> What about dma_direct_free_pages()? Nothing inside uses attrs, but
> that’s quite similar to dma_direct_alloc_pages()
>
> Also, at this point, shouldn’t this patch also remove
> force_dma_unencrypted() calls from dma_set_decrypted() and
> dma_set_encrypted()?
>
The final change have
void dma_direct_free_pages(struct device *dev, size_t size,
...
{
/*
* if the device had requested for an unencrypted buffer,
* convert it to encrypted on free
*/
bool mark_mem_encrypted = force_dma_unencrypted(dev);
That got added by "dma-direct: select DMA address encoding from
DMA_ATTR_CC_SHARED "
I'll move that hunk into this patch. The overall goal is
dma_direct_alloc(.. attrs)
{
if (force_dma_unencrypted(dev))
attrs |= DMA_ATTR_CC_SHARED;
}
dma_direct_free(.. attrs)
{
if (force_dma_unencrypted(dev)) {
attrs |= DMA_ATTR_CC_SHARED;
mark_mem_encrypted = true;
}
if (swiotlb_find_pool(dev, dma_to_phys(dev, dma_addr)))
mark_mem_encrypted = false;
}
dma_direct_alloc_pages()
{
if (force_dma_unencrypted(dev))
attrs |= DMA_ATTR_CC_SHARED;
}
dma_direct_free_pages()
{
bool mark_mem_encrypted = force_dma_unencrypted(dev);
if (swiotlb_find_pool(dev, page_to_phys(page)))
mark_mem_encrypted = false;
}
-aneesh
