[PATCH v6 6/9] swiotlb: Reject misaligned restricted DMA pools for CoCo guests
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Date: 2026-09-04 10:35:36
Also in:
kvmarm, linux-coco, linux-iommu, lkml
Subsystem:
dma mapping helpers, the rest · Maintainers:
Marek Szyprowski, Linus Torvalds
Restricted DMA pools are described by firmware reserved-memory nodes and are not resized or realigned by the kernel. For confidential-computing guests, such pools can only be shared safely when both the base address and size are aligned to the shared-granule size. Reject restricted DMA pools that are not aligned to mem_cc_shared_granule_size() when guest memory encryption is active. Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org> --- kernel/dma/swiotlb.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index f8936b03d942..d1bd06be628d 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c@@ -2037,6 +2037,20 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem, * if platform supports memory encryption, * restricted mem pool is shared by default */ + if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) { + size_t cc_shared_granule_size = mem_cc_shared_granule_size(); + + if (!IS_ALIGNED(rmem->base, cc_shared_granule_size) || + !IS_ALIGNED(rmem->size, cc_shared_granule_size)) { + dev_err(dev, "Restricted DMA pool must be aligned to %#zx bytes for memory encryption\n", + cc_shared_granule_size); + kfree(pool->areas); + kfree(pool->slots); + kfree(mem); + return -EINVAL; + } + } + if (cc_platform_has(CC_ATTR_MEM_ENCRYPT)) { int ret;
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2.43.0