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Tue, 09 Jun 2026 05:15:55 -0700 (PDT) Date: Tue, 9 Jun 2026 14:15:48 +0200 From: Petr Tesarik To: "Aneesh Kumar K.V (Arm)" Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, Robin Murphy , Marek Szyprowski , Will Deacon , Marc Zyngier , Steven Price , Suzuki K Poulose , Catalin Marinas , Jiri Pirko , Jason Gunthorpe , Mostafa Saleh , Alexey Kardashevskiy , Dan Williams , Xu Yilun , linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Alexander Gordeev , Gerald Schaefer , Heiko Carstens , Vasily Gorbik , Christian Borntraeger , Sven Schnelle , x86@kernel.org, Jiri Pirko , Michael Kelley Subject: Re: [PATCH v6 02/20] dma-direct: swiotlb: handle swiotlb alloc/free outside __dma_direct_alloc_pages Message-ID: <20260609141548.70a5848d@mordecai> In-Reply-To: <20260604083959.1265923-3-aneesh.kumar@kernel.org> References: <20260604083959.1265923-1-aneesh.kumar@kernel.org> <20260604083959.1265923-3-aneesh.kumar@kernel.org> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-suse-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Thu, 4 Jun 2026 14:09:41 +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. > > Tested-by: Jiri Pirko > Tested-by: Michael Kelley > Tested-by: Mostafa Saleh > Signed-off-by: Aneesh Kumar K.V (Arm) > --- > include/linux/swiotlb.h | 6 ++++ > kernel/dma/direct.c | 71 ++++++++++++++++++++++++++++++----------- > kernel/dma/swiotlb.c | 6 ++++ > 3 files changed, 65 insertions(+), 18 deletions(-) > > diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h > index 3dae0f592063..133bb8ca9032 100644 > --- a/include/linux/swiotlb.h > +++ b/include/linux/swiotlb.h > @@ -284,6 +284,8 @@ extern void swiotlb_print_info(void); > #ifdef CONFIG_DMA_RESTRICTED_POOL > struct page *swiotlb_alloc(struct device *dev, size_t size); > bool swiotlb_free(struct device *dev, struct page *page, size_t size); > +void swiotlb_free_from_pool(struct device *dev, phys_addr_t tlb_addr, > + size_t size, struct io_tlb_pool *pool); > > static inline bool is_swiotlb_for_alloc(struct device *dev) > { > @@ -299,6 +301,10 @@ static inline bool swiotlb_free(struct device *dev, struct page *page, > { > return false; > } > +static inline void swiotlb_free_from_pool(struct device *dev, phys_addr_t tlb_addr, > + size_t size, struct io_tlb_pool *pool) > +{ > +} > static inline bool is_swiotlb_for_alloc(struct device *dev) > { > return false; > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 583c5922bca2..a741c8a2ee66 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -96,14 +96,6 @@ static int dma_set_encrypted(struct device *dev, void *vaddr, size_t size) > return ret; > } > > -static void __dma_direct_free_pages(struct device *dev, struct page *page, > - size_t size) > -{ > - if (swiotlb_free(dev, page, size)) > - return; > - dma_free_contiguous(dev, page, size); > -} > - > static struct page *dma_direct_alloc_swiotlb(struct device *dev, size_t size) > { > struct page *page = swiotlb_alloc(dev, size); > @@ -125,9 +117,6 @@ 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 +193,7 @@ 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 +240,21 @@ 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 +281,7 @@ 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)) > goto out_leak_pages; > } > > @@ -298,10 +298,11 @@ 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); > + if (!swiotlb_free(dev, page, size)) > + dma_free_contiguous(dev, page, size); > return NULL; > out_leak_pages: > return NULL; > @@ -310,6 +311,9 @@ 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) > { > + phys_addr_t phys; > + bool mark_mem_encrypted = true; > + struct io_tlb_pool *swiotlb_pool; > unsigned int page_order = get_order(size); > > if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && > @@ -338,16 +342,25 @@ void dma_direct_free(struct device *dev, size_t size, > dma_free_from_pool(dev, cpu_addr, PAGE_ALIGN(size))) > return; > > + phys = dma_to_phys(dev, dma_addr); > + swiotlb_pool = swiotlb_find_pool(dev, phys); > + if (swiotlb_pool) > + /* Swiotlb doesn't need a page attribute update on free */ > + 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; > } > > - __dma_direct_free_pages(dev, dma_direct_to_page(dev, dma_addr), size); > + if (swiotlb_pool) > + swiotlb_free_from_pool(dev, phys, size, swiotlb_pool); > + else > + dma_free_contiguous(dev, dma_direct_to_page(dev, dma_addr), size); > } > > struct page *dma_direct_alloc_pages(struct device *dev, size_t size, > @@ -359,6 +372,15 @@ 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; > + > + ret = page_address(page); > + goto setup_page; > + } > + > page = __dma_direct_alloc_pages(dev, size, gfp, false); > if (!page) > return NULL; > @@ -366,6 +388,7 @@ 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; > @@ -377,16 +400,28 @@ void dma_direct_free_pages(struct device *dev, size_t size, > struct page *page, dma_addr_t dma_addr, > enum dma_data_direction dir) > { > + phys_addr_t phys; > void *vaddr = page_address(page); > + struct io_tlb_pool *swiotlb_pool; > + 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)) > + phys = page_to_phys(page); > + swiotlb_pool = swiotlb_find_pool(dev, phys); > + if (swiotlb_pool) > + mark_mem_encrypted = false; > + > + if (mark_mem_encrypted && dma_set_encrypted(dev, vaddr, size)) > return; > - __dma_direct_free_pages(dev, page, size); > + > + if (swiotlb_pool) > + swiotlb_free_from_pool(dev, phys, size, swiotlb_pool); > + else > + dma_free_contiguous(dev, page, size); > } > > #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \ > diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c > index 1abd3e6146f4..ac03a6856c2e 100644 > --- a/kernel/dma/swiotlb.c > +++ b/kernel/dma/swiotlb.c > @@ -1809,6 +1809,12 @@ bool swiotlb_free(struct device *dev, struct page *page, size_t size) > return true; > } > > +void swiotlb_free_from_pool(struct device *dev, phys_addr_t tlb_addr, size_t size, > + struct io_tlb_pool *pool) What's the reason to pass the buffer size if it's not used? Other than that, this patch looks good to me. Petr T > +{ > + swiotlb_release_slots(dev, tlb_addr, pool); > +} > + > static int rmem_swiotlb_device_init(struct reserved_mem *rmem, > struct device *dev) > {