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Wed, 9 Sep 2026 20:34:03 -0700 From: Nicolin Chen To: Jason Gunthorpe , Catalin Marinas , Will Deacon , , Robin Murphy , , Danilo Krummrich , Marek Szyprowski , CC: Mark Rutland , Greg Kroah-Hartman , Suzuki K Poulose , Gavin Shan , Vikram Sethi , "Anshuman Khandual" , Shanker Donthineni , Mostafa Saleh , , Thomas Huth , Marc Zyngier , Ryan Roberts , , Kohei Enju , Shaopeng Tan , Ard Biesheuvel , James Morse , Steven Price , Sang-Heon Jeon , Omar Sandoval , Andrew Morton , Jinjie Ruan , Sam Edwards , Douglas Anderson , "Florian Fainelli" , Chen-Yu Tsai , Huacai Chen , Thomas Zimmermann , Pranjal Shrivastava , Ashish Mhetre , Shameer Kolothum , , , , , Sonang Patel , Ankit Agrawal Subject: [PATCH v1 4/8] dma-mapping: Keep DMA memory private for capable devices Date: Wed, 9 Sep 2026 20:32:47 -0700 Message-ID: X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-NV-OnPremToCloud: ExternallySecured X-EOPAttributedMessage: 0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SJ1PEPF00002315:EE_|CH0PR12MB8487:EE_ X-MS-Office365-Filtering-Correlation-Id: 022bb3dc-e09c-4dcc-5a39-08df0eec643b X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|376014|7416014|1800799024|36860700016|23010399003|82310400026|10067099003|11063799006|5023799004|56012099006|18002099003|22082099003; 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This makes the DMA API use shared memory for coherent allocations and bounce streaming mappings through SWIOTLB. A device marked with DEV_FLAG_DMA_CC_PRIVATE can reach private memory directly. Add dma_require_decrypted() to combine force_dma_unencrypted() with the new device flag, and use it throughout the generic DMA code. Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Nicolin Chen --- include/linux/dma-direct.h | 7 ++++++- kernel/dma/direct.c | 16 ++++++++-------- kernel/dma/mapping.c | 2 +- kernel/dma/swiotlb.c | 2 +- 4 files changed, 16 insertions(+), 11 deletions(-) diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h index daa31a1adf7b0..fb35ca27941cc 100644 --- a/include/linux/dma-direct.h +++ b/include/linux/dma-direct.h @@ -134,6 +134,11 @@ static inline bool force_dma_unencrypted(struct device *dev) } #endif /* CONFIG_ARCH_HAS_FORCE_DMA_UNENCRYPTED */ +static inline bool dma_require_decrypted(struct device *dev) +{ + return !dev_dma_cc_private(dev) && force_dma_unencrypted(dev); +} + static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, bool is_ram, unsigned long attrs) { @@ -146,7 +151,7 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size, * requires unencrypted DMA addresses. Treat it as not DMA-capable * so the caller can fall back to a suitable SWIOTLB pool. */ - if (!(attrs & DMA_ATTR_CC_SHARED) && force_dma_unencrypted(dev)) + if (!(attrs & DMA_ATTR_CC_SHARED) && dma_require_decrypted(dev)) return false; if (is_ram && !IS_ENABLED(CONFIG_ARCH_DMA_ADDR_T_64BIT) && diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index da665ca22d5c0..fbddab9740162 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -41,7 +41,7 @@ static inline struct page *dma_direct_to_page(struct device *dev, u64 dma_direct_get_required_mask(struct device *dev) { - bool require_decrypted = force_dma_unencrypted(dev); + bool require_decrypted = dma_require_decrypted(dev); phys_addr_t phys = ((phys_addr_t)max_pfn << PAGE_SHIFT) - 1; u64 max_dma = phys_to_dma_direct(dev, phys, require_decrypted); @@ -72,7 +72,7 @@ static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 *phys_limit) bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) { - bool require_decrypted = force_dma_unencrypted(dev); + bool require_decrypted = dma_require_decrypted(dev); dma_addr_t dma_addr = phys_to_dma_direct(dev, phys, require_decrypted); if (dma_addr == DMA_MAPPING_ERROR) @@ -208,7 +208,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, struct page *page; void *cpu_addr; - if (force_dma_unencrypted(dev)) + if (dma_require_decrypted(dev)) attrs |= __DMA_ATTR_ALLOC_CC_SHARED; if (attrs & __DMA_ATTR_ALLOC_CC_SHARED) { @@ -368,7 +368,7 @@ void dma_direct_free(struct device *dev, size_t size, * If the allocation used decrypted/shared backing pages, restore * the encryption state on free. */ - if (force_dma_unencrypted(dev)) + if (dma_require_decrypted(dev)) attrs |= __DMA_ATTR_ALLOC_CC_SHARED; if (attrs & __DMA_ATTR_ALLOC_CC_SHARED) @@ -436,7 +436,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size, struct page *page; void *cpu_addr; - if (force_dma_unencrypted(dev)) + if (dma_require_decrypted(dev)) attrs |= __DMA_ATTR_ALLOC_CC_SHARED; if ((attrs & __DMA_ATTR_ALLOC_CC_SHARED) && dma_direct_use_pool(dev, gfp)) @@ -480,7 +480,7 @@ 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); + bool mark_mem_encrypted = dma_require_decrypted(dev); /* If page is not from an atomic pool, dma_free_from_pool_page() fails */ if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) && @@ -649,7 +649,7 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma, const pgoff_t pgoff_end = vma_end_pgoff(vma); int ret = -ENXIO; - if (force_dma_unencrypted(dev)) + if (dma_require_decrypted(dev)) attrs |= DMA_ATTR_CC_SHARED; vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs); @@ -798,7 +798,7 @@ size_t dma_direct_max_mapping_size(struct device *dev) /* If SWIOTLB is active, use its maximum mapping size */ if (is_swiotlb_active(dev) && (dma_addressing_limited(dev) || is_swiotlb_force_bounce(dev) || - force_dma_unencrypted(dev))) + dma_require_decrypted(dev))) return swiotlb_max_mapping_size(dev); return SIZE_MAX; diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c index 11c127ad45370..e7c48a925b7ac 100644 --- a/kernel/dma/mapping.c +++ b/kernel/dma/mapping.c @@ -673,7 +673,7 @@ void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle, return NULL; } - if (force_dma_unencrypted(dev)) + if (dma_require_decrypted(dev)) attrs |= __DMA_ATTR_ALLOC_CC_SHARED; if (dma_alloc_from_dev_coherent(dev, size, dma_handle, &cpu_addr)) { diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index ded7016a46a71..d08a3643ded14 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -1552,7 +1552,7 @@ phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr, if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) { /* swiotlb pool is incorrect for this device */ - if (unlikely(mem->cc_shared != force_dma_unencrypted(dev))) + if (unlikely(mem->cc_shared != dma_require_decrypted(dev))) return (phys_addr_t)DMA_MAPPING_ERROR; } else if (cc_platform_has(CC_ATTR_HOST_MEM_ENCRYPT)) { -- 2.43.0