[RFC PATCH v7 08/13] dma-direct: Align CoCo shared DMA allocations to the shared granule size
Aneesh Kumar K.V (Arm)
aneesh.kumar at kernel.org
Mon Sep 21 07:48:42 PDT 2026
Use the common CoCo shared-memory geometry helpers for allocations
backed directly by CMA or the page allocator. Round the backing
allocation to a whole shared granule, pass the required alignment order
through the DMA contiguous allocator, and transition the complete range
through the common shared/private helpers.
Recompute the layout before freeing ordinary direct allocations so the
transition back to private memory and dma_free_contiguous() cover
exactly the range acquired by the allocation path. If restoring private
state fails, retain the existing fail-safe behavior and leak the pages
rather than returning potentially shared memory to the allocator.
This also applies the same rules to dma_direct_alloc_pages(), covering
callers which require a struct page result rather than a CPU virtual
address.
Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar at kernel.org>
---
kernel/dma/direct.c | 55 +++++++++++++++++++++++++++++++++++----------
1 file changed, 43 insertions(+), 12 deletions(-)
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index d968a0c81e73..d293198384c3 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -11,10 +11,10 @@
#include <linux/scatterlist.h>
#include <linux/pfn.h>
#include <linux/vmalloc.h>
-#include <linux/set_memory.h>
#include <linux/slab.h>
#include <linux/pci-p2pdma.h>
#include <linux/cc_platform.h>
+#include <linux/cc_shared.h>
#include "direct.h"
@@ -85,7 +85,7 @@ static int dma_set_decrypted(struct device *dev, void *vaddr, size_t size)
{
int ret;
- ret = set_memory_decrypted((unsigned long)vaddr, PFN_UP(size));
+ ret = cc_make_shared(vaddr, size);
if (ret)
pr_warn_ratelimited("leaking DMA memory that can't be decrypted\n");
return ret;
@@ -95,7 +95,7 @@ static int dma_set_encrypted(struct device *dev, void *vaddr, size_t size)
{
int ret;
- ret = set_memory_encrypted((unsigned long)vaddr, PFN_UP(size));
+ ret = cc_make_private(vaddr, size);
if (ret)
pr_warn_ratelimited("leaking DMA memory that can't be re-encrypted\n");
return ret;
@@ -115,7 +115,7 @@ static struct page *dma_direct_alloc_swiotlb(struct device *dev, size_t size,
}
static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
- gfp_t gfp, bool allow_highmem)
+ gfp_t gfp, bool allow_highmem, unsigned int align_order)
{
int node = dev_to_node(dev);
struct page *page;
@@ -124,7 +124,7 @@ static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
WARN_ON_ONCE(!PAGE_ALIGNED(size));
gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit);
- page = dma_alloc_contiguous(dev, size, gfp, 0);
+ page = dma_alloc_contiguous(dev, size, gfp, align_order);
if (page) {
if (dma_coherent_ok(dev, page_to_phys(page), size) &&
(allow_highmem || !PageHighMem(page)))
@@ -184,7 +184,7 @@ static void *dma_direct_alloc_no_mapping(struct device *dev, size_t size,
{
struct page *page;
- page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true);
+ page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true, 0);
if (!page)
return NULL;
@@ -205,6 +205,8 @@ void *dma_direct_alloc(struct device *dev, size_t size,
bool remap = false, set_uncached = false;
bool mark_mem_decrypt = false;
bool allow_highmem = true;
+ struct cc_shared_layout layout;
+ unsigned int align_order = 0;
struct page *page;
void *cpu_addr;
@@ -285,8 +287,16 @@ void *dma_direct_alloc(struct device *dev, size_t size,
return NULL;
}
+ if (mark_mem_decrypt) {
+ if (cc_shared_calc_layout(size, &layout))
+ return NULL;
+ size = layout.shared_size;
+ align_order = get_order(layout.alignment);
+ }
+
/* we always manually zero the memory once we are done */
- page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, allow_highmem);
+ page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO,
+ allow_highmem, align_order);
if (!page)
return NULL;
@@ -305,7 +315,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
void *lm_addr;
lm_addr = page_address(page);
- if (set_memory_decrypted((unsigned long)lm_addr, PFN_UP(size)))
+ if (dma_set_decrypted(dev, lm_addr, size))
goto out_leak_pages;
}
@@ -362,6 +372,7 @@ void dma_direct_free(struct device *dev, size_t size,
phys_addr_t phys;
bool mark_mem_encrypted = false;
struct io_tlb_pool *swiotlb_pool;
+ struct cc_shared_layout layout;
unsigned int page_order = get_order(size);
/*
@@ -406,6 +417,12 @@ void dma_direct_free(struct device *dev, size_t size,
/* Swiotlb doesn't need a page attribute update on free */
mark_mem_encrypted = false;
+ if (mark_mem_encrypted) {
+ if (WARN_ON_ONCE(cc_shared_calc_layout(size, &layout)))
+ return;
+ size = layout.shared_size;
+ }
+
if (is_vmalloc_addr(cpu_addr)) {
vunmap(cpu_addr);
} else {
@@ -417,10 +434,8 @@ void dma_direct_free(struct device *dev, size_t size,
void *lm_addr;
lm_addr = phys_to_virt(phys);
- if (set_memory_encrypted((unsigned long)lm_addr, PFN_UP(size))) {
- pr_warn_ratelimited("leaking DMA memory that can't be re-encrypted\n");
+ if (dma_set_encrypted(dev, lm_addr, size))
return;
- }
}
if (swiotlb_pool)
@@ -433,6 +448,8 @@ 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 cc_shared_layout layout;
+ unsigned int align_order = 0;
struct page *page;
void *cpu_addr;
@@ -452,7 +469,14 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
goto setup_page;
}
- page = __dma_direct_alloc_pages(dev, size, gfp, false);
+ if (attrs & __DMA_ATTR_ALLOC_CC_SHARED) {
+ if (cc_shared_calc_layout(size, &layout))
+ return NULL;
+ size = layout.shared_size;
+ align_order = get_order(layout.alignment);
+ }
+
+ page = __dma_direct_alloc_pages(dev, size, gfp, false, align_order);
if (!page)
return NULL;
@@ -476,6 +500,7 @@ void dma_direct_free_pages(struct device *dev, size_t size,
phys_addr_t phys;
void *vaddr = page_address(page);
struct io_tlb_pool *swiotlb_pool;
+ struct cc_shared_layout layout;
/*
* if the device had requested for an unencrypted buffer,
* convert it to encrypted on free
@@ -492,6 +517,12 @@ void dma_direct_free_pages(struct device *dev, size_t size,
if (swiotlb_pool)
mark_mem_encrypted = false;
+ if (mark_mem_encrypted) {
+ if (WARN_ON_ONCE(cc_shared_calc_layout(size, &layout)))
+ return;
+ size = layout.shared_size;
+ }
+
if (mark_mem_encrypted && dma_set_encrypted(dev, vaddr, size))
return;
--
2.43.0
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