[PATCH v6 5/9] swiotlb: Align shared IO TLB pools to the shared granule size
From: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>
Date: 2026-09-04 10:35:30
Also in:
kvmarm, linux-coco, linux-iommu, lkml
Subsystem:
dma mapping helpers, the rest · Maintainers:
Marek Szyprowski, Linus Torvalds
swiotlb pools used by confidential-computing guests are shared with the host and therefore must be converted at the host shared-granule size. A PAGE_SIZE-sized or PAGE_SIZE-aligned pool is not sufficient when the host tracks shared state at a larger granularity. Round swiotlb pool sizes to mem_cc_shared_granule_size(), allocate the pools at that alignment, and use the same aligned size when decrypting, encrypting and freeing pool memory. Apply the same rule to dynamically allocated swiotlb pools. Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org> --- kernel/dma/swiotlb.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index ded7016a46a7..f8936b03d942 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c@@ -369,7 +369,8 @@ void __init swiotlb_update_mem_attributes(void) if (!mem->nslabs || mem->late_alloc) return; - bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT); + + bytes = mem_cc_align_to_shared_granule(mem->nslabs << IO_TLB_SHIFT); if (io_tlb_default_mem.cc_shared) { int ret;
@@ -436,8 +437,8 @@ static void __init *swiotlb_memblock_alloc(unsigned long nslabs, unsigned int flags, int (*remap)(void *tlb, unsigned long nslabs)) { - size_t bytes = PAGE_ALIGN(nslabs << IO_TLB_SHIFT); void *tlb; + size_t bytes = mem_cc_align_to_shared_granule(nslabs << IO_TLB_SHIFT); /* * By default allocate the bounce buffer memory from low memory, but
@@ -445,9 +446,9 @@ static void __init *swiotlb_memblock_alloc(unsigned long nslabs, * memory encryption. */ if (flags & SWIOTLB_ANY) - tlb = memblock_alloc(bytes, PAGE_SIZE); + tlb = memblock_alloc(bytes, mem_cc_shared_granule_size()); else - tlb = memblock_alloc_low(bytes, PAGE_SIZE); + tlb = memblock_alloc_low(bytes, mem_cc_shared_granule_size()); if (!tlb) { pr_warn("%s: Failed to allocate %zu bytes tlb structure\n",
@@ -456,7 +457,7 @@ static void __init *swiotlb_memblock_alloc(unsigned long nslabs, } if (remap && remap(tlb, nslabs) < 0) { - memblock_free(tlb, PAGE_ALIGN(bytes)); + memblock_free(tlb, bytes); pr_warn("%s: Failed to remap %zu bytes\n", __func__, bytes); return NULL; }
@@ -578,7 +579,7 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask, swiotlb_adjust_nareas(num_possible_cpus()); retry: - order = get_order(nslabs << IO_TLB_SHIFT); + order = get_order(mem_cc_align_to_shared_granule(nslabs << IO_TLB_SHIFT)); nslabs = SLABS_PER_PAGE << order; while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
@@ -587,6 +588,8 @@ int swiotlb_init_late(size_t size, gfp_t gfp_mask, if (vstart) break; order--; + if (order < get_order(mem_cc_shared_granule_size())) + break; nslabs = SLABS_PER_PAGE << order; retried = true; }
@@ -667,7 +670,7 @@ void __init swiotlb_exit(void) pr_info("tearing down default memory pool\n"); tbl_vaddr = (unsigned long)phys_to_virt(mem->start); - tbl_size = PAGE_ALIGN(mem->end - mem->start); + tbl_size = mem_cc_align_to_shared_granule(mem->end - mem->start); slots_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), mem->nslabs)); if (io_tlb_default_mem.cc_shared) {
@@ -711,12 +714,14 @@ void __init swiotlb_exit(void) static struct page *alloc_dma_pages(gfp_t gfp, size_t bytes, u64 phys_limit, unsigned long attrs) { - unsigned int order = get_order(bytes); bool cc_shared = attrs & __DMA_ATTR_ALLOC_CC_SHARED; + unsigned int order; struct page *page; phys_addr_t paddr; void *vaddr; + bytes = mem_cc_align_to_shared_granule(bytes); + order = get_order(bytes); page = alloc_pages(gfp, order); if (!page) return NULL;
@@ -807,6 +812,7 @@ static void swiotlb_free_tlb(void *vaddr, size_t bytes, bool cc_shared) dma_free_from_pool(NULL, vaddr, bytes)) return; + bytes = mem_cc_align_to_shared_granule(bytes); /* Intentional leak if pages cannot be encrypted again. */ if (!cc_shared || !set_memory_encrypted((unsigned long)vaddr, PFN_UP(bytes)))
--
2.43.0