From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: [PATCH 1/2] dma-mapping: support setting memory uncached in place Date: Thu, 7 Nov 2019 18:40:34 +0100 Message-ID: <20191107174035.13783-2-hch@lst.de> References: <20191107174035.13783-1-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20191107174035.13783-1-hch@lst.de> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Jonas Bonn , Stefan Kristiansson , Stafford Horne Cc: Mark Rutland , linux-arch@vger.kernel.org, Robin Murphy , linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, openrisc@lists.librecores.org, Will Deacon , linux-arm-kernel@lists.infradead.org, Marek Szyprowski List-Id: linux-arch.vger.kernel.org We currently only support remapping memory as uncached through vmap or a magic uncached segment provided by some architectures. But there is a simpler and much better way available on some architectures where we can just remap the memory in place. The advantages are: 1) no aliasing is possible, which prevents speculating into the cached alias 2) there is no need to allocate new ptes and thus no need for a special pre-allocated pool of memory that can be used with GFP_ATOMIC DMA allocations The downside is that architectures must provide a way to set arbitrary pages uncached in the kernel mapping, which might not be possible on architecture that have a special implicit kernel mapping, and requires splitting of huge page kernel mappings where they exist. Signed-off-by: Christoph Hellwig --- include/linux/dma-noncoherent.h | 3 +++ kernel/dma/Kconfig | 8 ++++++++ kernel/dma/direct.c | 28 ++++++++++++++++++---------- 3 files changed, 29 insertions(+), 10 deletions(-) diff --git a/include/linux/dma-noncoherent.h b/include/linux/dma-noncoherent.h index e30fca1f1b12..c4be9697279a 100644 --- a/include/linux/dma-noncoherent.h +++ b/include/linux/dma-noncoherent.h @@ -111,4 +111,7 @@ static inline void arch_dma_prep_coherent(struct page *page, size_t size) void *uncached_kernel_address(void *addr); void *cached_kernel_address(void *addr); +int arch_dma_set_uncached(void *cpu_addr, size_t size); +void arch_dma_clear_uncached(void *cpu_addr, size_t size); + #endif /* _LINUX_DMA_NONCOHERENT_H */ diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index 4c103a24e380..7bc0b77f1243 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -83,6 +83,14 @@ config DMA_DIRECT_REMAP bool select DMA_REMAP +# +# Should be selected if the architecture can remap memory from the page +# allocator and CMA as uncached and provides the arch_dma_set_uncached and +# arch_dma_clear_uncached helpers +# +config ARCH_HAS_DMA_SET_UNCACHED + bool + config DMA_CMA bool "DMA Contiguous Memory Allocator" depends on HAVE_DMA_CONTIGUOUS && CMA diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index e37e7ab6e2ee..e2b46001c1b3 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -171,11 +171,8 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, ret = dma_common_contiguous_remap(page, PAGE_ALIGN(size), dma_pgprot(dev, PAGE_KERNEL, attrs), __builtin_return_address(0)); - if (!ret) { - dma_free_contiguous(dev, page, size); - return ret; - } - + if (!ret) + goto out_free_pages; memset(ret, 0, size); goto done; } @@ -188,8 +185,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, * so log an error and fail. */ dev_info(dev, "Rejecting highmem page from CMA.\n"); - dma_free_contiguous(dev, page, size); - return NULL; + goto out_free_pages; } ret = page_address(page); @@ -198,10 +194,15 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, memset(ret, 0, size); - if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) && - dma_alloc_need_uncached(dev, attrs)) { + if (dma_alloc_need_uncached(dev, attrs)) { arch_dma_prep_coherent(page, size); - ret = uncached_kernel_address(ret); + + if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) { + if (!arch_dma_set_uncached(ret, size)) + goto out_free_pages; + } else if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT)) { + ret = uncached_kernel_address(ret); + } } done: if (force_dma_unencrypted(dev)) @@ -209,6 +210,9 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, else *dma_handle = phys_to_dma(dev, page_to_phys(page)); return ret; +out_free_pages: + dma_free_contiguous(dev, page, size); + return NULL; } void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr, @@ -232,6 +236,8 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr, if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) vunmap(cpu_addr); + else if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) + arch_dma_clear_uncached(cpu_addr, size); dma_free_contiguous(dev, dma_direct_to_page(dev, dma_addr), size); } @@ -240,6 +246,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) { if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) && + !IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && dma_alloc_need_uncached(dev, attrs)) return arch_dma_alloc(dev, size, dma_handle, gfp, attrs); @@ -250,6 +257,7 @@ void dma_direct_free(struct device *dev, size_t size, void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs) { if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) && + !IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && dma_alloc_need_uncached(dev, attrs)) arch_dma_free(dev, size, cpu_addr, dma_addr, attrs); -- 2.20.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:49990 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727132AbfKGRkz (ORCPT ); Thu, 7 Nov 2019 12:40:55 -0500 From: Christoph Hellwig Subject: [PATCH 1/2] dma-mapping: support setting memory uncached in place Date: Thu, 7 Nov 2019 18:40:34 +0100 Message-ID: <20191107174035.13783-2-hch@lst.de> In-Reply-To: <20191107174035.13783-1-hch@lst.de> References: <20191107174035.13783-1-hch@lst.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Jonas Bonn , Stefan Kristiansson , Stafford Horne Cc: Marek Szyprowski , Robin Murphy , Will Deacon , Mark Rutland , openrisc@lists.librecores.org, iommu@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <20191107174034.10qWvFczBCaHfBoZuCyJk5ZE4eIEPE9_EVpSsVtzQgA@z> We currently only support remapping memory as uncached through vmap or a magic uncached segment provided by some architectures. But there is a simpler and much better way available on some architectures where we can just remap the memory in place. The advantages are: 1) no aliasing is possible, which prevents speculating into the cached alias 2) there is no need to allocate new ptes and thus no need for a special pre-allocated pool of memory that can be used with GFP_ATOMIC DMA allocations The downside is that architectures must provide a way to set arbitrary pages uncached in the kernel mapping, which might not be possible on architecture that have a special implicit kernel mapping, and requires splitting of huge page kernel mappings where they exist. Signed-off-by: Christoph Hellwig --- include/linux/dma-noncoherent.h | 3 +++ kernel/dma/Kconfig | 8 ++++++++ kernel/dma/direct.c | 28 ++++++++++++++++++---------- 3 files changed, 29 insertions(+), 10 deletions(-) diff --git a/include/linux/dma-noncoherent.h b/include/linux/dma-noncoherent.h index e30fca1f1b12..c4be9697279a 100644 --- a/include/linux/dma-noncoherent.h +++ b/include/linux/dma-noncoherent.h @@ -111,4 +111,7 @@ static inline void arch_dma_prep_coherent(struct page *page, size_t size) void *uncached_kernel_address(void *addr); void *cached_kernel_address(void *addr); +int arch_dma_set_uncached(void *cpu_addr, size_t size); +void arch_dma_clear_uncached(void *cpu_addr, size_t size); + #endif /* _LINUX_DMA_NONCOHERENT_H */ diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index 4c103a24e380..7bc0b77f1243 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -83,6 +83,14 @@ config DMA_DIRECT_REMAP bool select DMA_REMAP +# +# Should be selected if the architecture can remap memory from the page +# allocator and CMA as uncached and provides the arch_dma_set_uncached and +# arch_dma_clear_uncached helpers +# +config ARCH_HAS_DMA_SET_UNCACHED + bool + config DMA_CMA bool "DMA Contiguous Memory Allocator" depends on HAVE_DMA_CONTIGUOUS && CMA diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c index e37e7ab6e2ee..e2b46001c1b3 100644 --- a/kernel/dma/direct.c +++ b/kernel/dma/direct.c @@ -171,11 +171,8 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, ret = dma_common_contiguous_remap(page, PAGE_ALIGN(size), dma_pgprot(dev, PAGE_KERNEL, attrs), __builtin_return_address(0)); - if (!ret) { - dma_free_contiguous(dev, page, size); - return ret; - } - + if (!ret) + goto out_free_pages; memset(ret, 0, size); goto done; } @@ -188,8 +185,7 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, * so log an error and fail. */ dev_info(dev, "Rejecting highmem page from CMA.\n"); - dma_free_contiguous(dev, page, size); - return NULL; + goto out_free_pages; } ret = page_address(page); @@ -198,10 +194,15 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, memset(ret, 0, size); - if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) && - dma_alloc_need_uncached(dev, attrs)) { + if (dma_alloc_need_uncached(dev, attrs)) { arch_dma_prep_coherent(page, size); - ret = uncached_kernel_address(ret); + + if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) { + if (!arch_dma_set_uncached(ret, size)) + goto out_free_pages; + } else if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT)) { + ret = uncached_kernel_address(ret); + } } done: if (force_dma_unencrypted(dev)) @@ -209,6 +210,9 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size, else *dma_handle = phys_to_dma(dev, page_to_phys(page)); return ret; +out_free_pages: + dma_free_contiguous(dev, page, size); + return NULL; } void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr, @@ -232,6 +236,8 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr, if (IS_ENABLED(CONFIG_DMA_REMAP) && is_vmalloc_addr(cpu_addr)) vunmap(cpu_addr); + else if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED)) + arch_dma_clear_uncached(cpu_addr, size); dma_free_contiguous(dev, dma_direct_to_page(dev, dma_addr), size); } @@ -240,6 +246,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) { if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) && + !IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && dma_alloc_need_uncached(dev, attrs)) return arch_dma_alloc(dev, size, dma_handle, gfp, attrs); @@ -250,6 +257,7 @@ void dma_direct_free(struct device *dev, size_t size, void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs) { if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) && + !IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && dma_alloc_need_uncached(dev, attrs)) arch_dma_free(dev, size, cpu_addr, dma_addr, attrs); -- 2.20.1