[PATCH] dma-buf: move system_cc_shared heap under separate Kconfig
From: Sumit Semwal <sumit.semwal@linaro.org>
Date: 2026-06-10 14:23:50
Also in:
dri-devel, linux-media, linux-s390, lkml
Subsystem:
dma buffer sharing framework, dma-buf heaps framework, the rest · Maintainers:
Sumit Semwal, Christian König, Linus Torvalds
From: Arnd Bergmann <arnd@arndb.de>
While system heap and system_cc_shared heap share a lot of code
and hence the same source file, their users have different needs.
system heap users need it to be a loadable module, while
system_cc_shared heap users don't.
Building as a loadable module breaks system_cc_shared heap on
powerpc and s390 due to un-exported set_memory_encrypted /
set_memory_decrypted functions.
Fix these by reorganising code to put the system_cc_shared heap
under a new Kconfig symbol, which allows either building both
into the kernel, or leave encryption up to the consumers of the
system heap.
Fixes: fd55edff8a0a ("dma-buf: heaps: system: Turn the heap into a module")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
---
drivers/dma-buf/heaps/Kconfig | 8 ++++++++
drivers/dma-buf/heaps/system_heap.c | 16 ++++++++++------
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig
index e273fb18feca..a39decdcf067 100644
--- a/drivers/dma-buf/heaps/Kconfig
+++ b/drivers/dma-buf/heaps/Kconfig@@ -5,6 +5,14 @@ config DMABUF_HEAPS_SYSTEM Choose this option to enable the system dmabuf heap. The system heap is backed by pages from the buddy allocator. If in doubt, say Y. +config DMABUF_HEAPS_CC_SYSTEM + bool "DMA-BUF System Heap for decrypted CoCo VMs" + depends on DMABUF_HEAPS && ARCH_HAS_MEM_ENCRYPT && DMABUF_HEAPS_SYSTEM=y + help + Choose this option to enable the system_cc_shared dmabuf heap. This + allows allocating shared (decrypted) memory for confidential computing + (CoCo) VMs. + config DMABUF_HEAPS_CMA tristate "DMA-BUF CMA Heap" depends on DMABUF_HEAPS && DMA_CMA
diff --git a/drivers/dma-buf/heaps/system_heap.c b/drivers/dma-buf/heaps/system_heap.c
index c92bdec356fc..71d9028cc3df 100644
--- a/drivers/dma-buf/heaps/system_heap.c
+++ b/drivers/dma-buf/heaps/system_heap.c@@ -48,6 +48,9 @@ struct dma_heap_attachment { bool cc_shared; }; +#define cc_shared_buffer(b) (IS_ENABLED(CONFIG_DMABUF_HEAPS_CC_SYSTEM) && \ + (b)->cc_shared) + #define LOW_ORDER_GFP (GFP_HIGHUSER | __GFP_ZERO) #define HIGH_ORDER_GFP (((GFP_HIGHUSER | __GFP_ZERO | __GFP_NOWARN \ | __GFP_NORETRY) & ~__GFP_RECLAIM) \
@@ -161,7 +164,7 @@ static struct sg_table *system_heap_map_dma_buf(struct dma_buf_attachment *attac unsigned long attrs; int ret; - attrs = a->cc_shared ? DMA_ATTR_CC_SHARED : 0; + attrs = cc_shared_buffer(a) ? DMA_ATTR_CC_SHARED : 0; ret = dma_map_sgtable(attachment->dev, table, direction, attrs); if (ret) return ERR_PTR(ret);
@@ -233,7 +236,7 @@ static int system_heap_mmap(struct dma_buf *dmabuf, struct vm_area_struct *vma) int i, ret; prot = vma->vm_page_prot; - if (buffer->cc_shared) + if (cc_shared_buffer(buffer)) prot = pgprot_decrypted(prot); for_each_sgtable_sg(table, sg, i) {
@@ -282,7 +285,7 @@ static void *system_heap_do_vmap(struct system_heap_buffer *buffer) } prot = PAGE_KERNEL; - if (buffer->cc_shared) + if (cc_shared_buffer(buffer)) prot = pgprot_decrypted(prot); vaddr = vmap(pages, npages, VM_MAP, prot); vfree(pages);
@@ -349,7 +352,7 @@ static void system_heap_dma_buf_release(struct dma_buf *dmabuf) * Intentionally leak pages that cannot be re-encrypted * to prevent shared memory from being reused. */ - if (buffer->cc_shared && + if (cc_shared_buffer(buffer) && system_heap_set_page_encrypted(page)) continue;
@@ -456,7 +459,7 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap, list_del(&page->lru); } - if (cc_shared) { + if (cc_shared_buffer(buffer)) { for_each_sgtable_sg(table, sg, i) { ret = system_heap_set_page_decrypted(sg_page(sg)); if (ret)
@@ -485,7 +488,7 @@ static struct dma_buf *system_heap_allocate(struct dma_heap *heap, * Intentionally leak pages that cannot be re-encrypted * to prevent shared memory from being reused. */ - if (buffer->cc_shared && + if (cc_shared_buffer(buffer) && system_heap_set_page_encrypted(p)) continue; __free_pages(p, compound_order(p));
@@ -525,6 +528,7 @@ static int __init system_heap_create(void) return PTR_ERR(sys_heap); if (IS_ENABLED(CONFIG_HIGHMEM) || + !IS_ENABLED(CONFIG_DMABUF_HEAPS_CC_SYSTEM) || !cc_platform_has(CC_ATTR_MEM_ENCRYPT)) return 0;
--
2.43.0