From: Mostafa Saleh <smostafa@google•com>
To: "Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel•org>
Cc: iommu@lists•linux.dev, linux-arm-kernel@lists•infradead.org,
linux-kernel@vger•kernel.org, linux-coco@lists•linux.dev,
Robin Murphy <robin.murphy@arm•com>,
Marek Szyprowski <m.szyprowski@samsung•com>,
Will Deacon <will@kernel•org>, Marc Zyngier <maz@kernel•org>,
Steven Price <steven.price@arm•com>,
Suzuki K Poulose <Suzuki.Poulose@arm•com>,
Catalin Marinas <catalin.marinas@arm•com>,
Jiri Pirko <jiri@resnulli•us>, Jason Gunthorpe <jgg@ziepe•ca>,
Petr Tesarik <ptesarik@suse•com>,
Alexey Kardashevskiy <aik@amd•com>,
Dan Williams <dan.j.williams@intel•com>,
Xu Yilun <yilun.xu@linux•intel.com>,
linuxppc-dev@lists•ozlabs.org, linux-s390@vger•kernel.org,
Madhavan Srinivasan <maddy@linux•ibm.com>,
Michael Ellerman <mpe@ellerman•id.au>,
Nicholas Piggin <npiggin@gmail•com>,
"Christophe Leroy (CS GROUP)" <chleroy@kernel•org>,
Alexander Gordeev <agordeev@linux•ibm.com>,
Gerald Schaefer <gerald.schaefer@linux•ibm.com>,
Heiko Carstens <hca@linux•ibm.com>,
Vasily Gorbik <gor@linux•ibm.com>,
Christian Borntraeger <borntraeger@linux•ibm.com>,
Sven Schnelle <svens@linux•ibm.com>,
x86@kernel•org
Subject: Re: [PATCH v4 01/13] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages
Date: Wed, 13 May 2026 13:57:16 +0000 [thread overview]
Message-ID: <agSDPJMZkcI-uH8f@google.com> (raw)
In-Reply-To: <20260512090408.794195-2-aneesh.kumar@kernel.org>
On Tue, May 12, 2026 at 02:33:56PM +0530, Aneesh Kumar K.V (Arm) wrote:
> Move swiotlb allocation out of __dma_direct_alloc_pages() and handle it in
> dma_direct_alloc() / dma_direct_alloc_pages().
>
> This is needed for follow-up changes that simplify the handling of
> memory encryption/decryption based on the DMA attribute flags.
>
> swiotlb backing pages are already mapped decrypted by
> swiotlb_update_mem_attributes() and rmem_swiotlb_device_init(), so
> dma-direct should not call dma_set_decrypted() on allocation nor
> dma_set_encrypted() on free for swiotlb-backed memory.
>
> Update alloc/free paths to detect swiotlb-backed pages and skip
> encrypt/decrypt transitions for those paths. Keep the existing highmem
> rejection in dma_direct_alloc_pages() for swiotlb allocations.
>
> Only for "restricted-dma-pool", we currently set `for_alloc = true`, while
> rmem_swiotlb_device_init() decrypts the whole pool up front. This pool is
> typically used together with "shared-dma-pool", where the shared region is
> accessed after remap/ioremap and the returned address is suitable for
> decrypted memory access. So existing code paths remain valid.
>
> Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel•org>
> ---
> kernel/dma/direct.c | 44 +++++++++++++++++++++++++++++++++++++-------
> 1 file changed, 37 insertions(+), 7 deletions(-)
>
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index ec887f443741..b958f150718a 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -125,9 +125,6 @@ static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
>
> WARN_ON_ONCE(!PAGE_ALIGNED(size));
>
> - if (is_swiotlb_for_alloc(dev))
> - return dma_direct_alloc_swiotlb(dev, size);
> -
> gfp |= dma_direct_optimal_gfp_mask(dev, &phys_limit);
> page = dma_alloc_contiguous(dev, size, gfp);
> if (page) {
> @@ -204,6 +201,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
> {
> bool remap = false, set_uncached = false;
> + bool mark_mem_decrypt = true;
> struct page *page;
> void *ret;
>
> @@ -250,11 +248,21 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> dma_direct_use_pool(dev, gfp))
> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
>
> + if (is_swiotlb_for_alloc(dev)) {
> + page = dma_direct_alloc_swiotlb(dev, size);
> + if (page) {
> + mark_mem_decrypt = false;
> + goto setup_page;
> + }
> + return NULL;
> + }
> +
> /* we always manually zero the memory once we are done */
> page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO, true);
> if (!page)
> return NULL;
>
> +setup_page:
> /*
> * dma_alloc_contiguous can return highmem pages depending on a
> * combination the cma= arguments and per-arch setup. These need to be
> @@ -281,7 +289,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> goto out_free_pages;
> } else {
> ret = page_address(page);
> - if (dma_set_decrypted(dev, ret, size))
> + if (mark_mem_decrypt && dma_set_decrypted(dev, ret, size))
I am ok with that approach, but Jason was mentioning we shouldn’t
special case swiotlb and make the allocator return the memory state
(similar to the dma_page [1]) . I am also OK if you want to merge that
part of my series with is.
[1] https://lore.kernel.org/linux-iommu/20260408194750.2280873-1-smostafa@google.com/
> goto out_leak_pages;
> }
>
> @@ -298,7 +306,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> return ret;
>
> out_encrypt_pages:
> - if (dma_set_encrypted(dev, page_address(page), size))
> + if (mark_mem_decrypt && dma_set_encrypted(dev, page_address(page), size))
> return NULL;
> out_free_pages:
> __dma_direct_free_pages(dev, page, size);
> @@ -310,6 +318,7 @@ void *dma_direct_alloc(struct device *dev, size_t size,
> void dma_direct_free(struct device *dev, size_t size,
> void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
> {
> + bool mark_mem_encrypted = true;
> unsigned int page_order = get_order(size);
>
> if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
> @@ -338,12 +347,15 @@ void dma_direct_free(struct device *dev, size_t size,
> dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size)))
> return;
>
> + if (swiotlb_find_pool(dev, dma_to_phys(dev, dma_addr)))
> + mark_mem_encrypted = false;
> +
> if (is_vmalloc_addr(cpu_addr)) {
> vunmap(cpu_addr);
> } else {
> if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CLEAR_UNCACHED))
> arch_dma_clear_uncached(cpu_addr, size);
> - if (dma_set_encrypted(dev, cpu_addr, size))
> + if (mark_mem_encrypted && dma_set_encrypted(dev, cpu_addr, size))
> return;
> }
>
> @@ -359,6 +371,19 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
> if (force_dma_unencrypted(dev) && dma_direct_use_pool(dev, gfp))
> return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
>
> + if (is_swiotlb_for_alloc(dev)) {
> + page = dma_direct_alloc_swiotlb(dev, size);
> + if (!page)
> + return NULL;
> +
> + if (PageHighMem(page)) {
My understanding is that rmem_swiotlb_device_init() asserts that there
is no PageHighMem()? Also a similar check doesn’t exist in
dma_direct_alloc().
Thanks,
Mostafa
> + swiotlb_free(dev, page, size);
> + return NULL;
> + }
> + ret = page_address(page);
> + goto setup_page;
> + }
> +
> page = __dma_direct_alloc_pages(dev, size, gfp, false);
> if (!page)
> return NULL;
> @@ -366,6 +391,7 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size,
> ret = page_address(page);
> if (dma_set_decrypted(dev, ret, size))
> goto out_leak_pages;
> +setup_page:
> memset(ret, 0, size);
> *dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
> return page;
> @@ -378,13 +404,17 @@ void dma_direct_free_pages(struct device *dev, size_t size,
> enum dma_data_direction dir)
> {
> void *vaddr = page_address(page);
> + bool mark_mem_encrypted = true;
>
> /* If cpu_addr is not from an atomic pool, dma_free_from_pool() fails */
> if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
> dma_free_from_pool(dev, vaddr, size))
> return;
>
> - if (dma_set_encrypted(dev, vaddr, size))
> + if (swiotlb_find_pool(dev, page_to_phys(page)))
> + mark_mem_encrypted = false;
> +
> + if (mark_mem_encrypted && dma_set_encrypted(dev, vaddr, size))
> return;
> __dma_direct_free_pages(dev, page, size);
> }
> --
> 2.43.0
>
next prev parent reply other threads:[~2026-05-13 13:57 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 9:03 [PATCH v4 00/13] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Aneesh Kumar K.V (Arm)
2026-05-12 9:03 ` [PATCH v4 01/13] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages Aneesh Kumar K.V (Arm)
2026-05-13 13:57 ` Mostafa Saleh [this message]
2026-05-14 4:54 ` Aneesh Kumar K.V
2026-05-12 9:03 ` [PATCH v4 02/13] dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths Aneesh Kumar K.V (Arm)
2026-05-13 13:58 ` Mostafa Saleh
2026-05-14 5:01 ` Aneesh Kumar K.V
2026-05-12 9:03 ` [PATCH v4 03/13] dma-pool: track decrypted atomic pools and select them via attrs Aneesh Kumar K.V (Arm)
2026-05-13 14:00 ` Mostafa Saleh
2026-05-14 7:00 ` Aneesh Kumar K.V
2026-05-14 8:06 ` Mostafa Saleh
2026-05-16 12:53 ` Alexey Kardashevskiy
2026-05-18 8:19 ` Alexey Kardashevskiy
2026-05-18 8:32 ` Aneesh Kumar K.V
2026-05-12 9:03 ` [PATCH v4 04/13] dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-05-13 14:27 ` Mostafa Saleh
2026-05-13 17:24 ` Jason Gunthorpe
2026-05-14 6:24 ` Aneesh Kumar K.V
2026-05-14 11:48 ` Mostafa Saleh
2026-05-14 12:35 ` Jason Gunthorpe
[not found] ` <agXfm3mS_M3fvRrN@google.com>
2026-05-15 22:51 ` Jason Gunthorpe
2026-05-19 11:06 ` Mostafa Saleh
2026-05-19 13:39 ` Jason Gunthorpe
2026-05-14 5:54 ` Aneesh Kumar K.V
2026-05-14 12:02 ` Mostafa Saleh
2026-05-14 12:48 ` Aneesh Kumar K.V
2026-05-14 14:21 ` Mostafa Saleh
2026-05-14 14:43 ` Aneesh Kumar K.V
2026-05-19 11:04 ` Mostafa Saleh
2026-05-19 12:27 ` Aneesh Kumar K.V
2026-05-19 15:07 ` Aneesh Kumar K.V
2026-05-19 15:27 ` Jason Gunthorpe
2026-05-19 16:05 ` Aneesh Kumar K.V
2026-05-19 16:11 ` Jason Gunthorpe
2026-05-20 3:57 ` Aneesh Kumar K.V
2026-05-20 13:40 ` Jason Gunthorpe
2026-05-19 13:29 ` Jason Gunthorpe
2026-05-19 13:41 ` Mostafa Saleh
2026-05-19 14:00 ` Aneesh Kumar K.V
2026-05-19 14:04 ` Mostafa Saleh
2026-05-19 14:17 ` Aneesh Kumar K.V
2026-05-19 14:27 ` Mostafa Saleh
2026-05-19 14:37 ` Jason Gunthorpe
2026-05-19 14:35 ` Jason Gunthorpe
2026-05-19 14:45 ` Mostafa Saleh
2026-05-19 14:49 ` Jason Gunthorpe
2026-05-14 14:37 ` Jason Gunthorpe
2026-05-18 8:19 ` Alexey Kardashevskiy
2026-05-21 17:06 ` Mostafa Saleh
2026-05-21 17:20 ` Aneesh Kumar K.V
2026-05-12 9:04 ` [PATCH v4 05/13] dma-mapping: make dma_pgprot() " Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 06/13] dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 07/13] dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-05-18 10:04 ` Christian Borntraeger
2026-05-21 15:37 ` Aneesh Kumar K.V
2026-05-12 9:04 ` [PATCH v4 08/13] dma-direct: set decrypted flag for remapped DMA allocations Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 09/13] dma-direct: select DMA address encoding from DMA_ATTR_CC_SHARED Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 10/13] dma-pool: fix page leak in atomic_pool_expand() cleanup Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 11/13] dma-direct: rename ret to cpu_addr in alloc helpers Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 12/13] dma-direct: return struct page from dma_direct_alloc_from_pool() Aneesh Kumar K.V (Arm)
2026-05-12 9:04 ` [PATCH v4 13/13] x86/amd-gart: preserve the direct DMA address until GART mapping succeeds Aneesh Kumar K.V (Arm)
2026-05-21 11:54 ` Aneesh Kumar K.V
2026-05-17 6:19 ` [PATCH v4 00/13] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths Jiri Pirko
2026-05-18 8:23 ` Aneesh Kumar K.V
2026-05-18 8:34 ` Jiri Pirko
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