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[209.85.128.53]) by smtp.gmail.com with ESMTPSA id u18sm1710388ejm.115.2020.10.14.06.20.28 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 14 Oct 2020 06:20:29 -0700 (PDT) Received: by mail-wm1-f53.google.com with SMTP id j136so2615705wmj.2 for ; Wed, 14 Oct 2020 06:20:28 -0700 (PDT) X-Received: by 2002:a7b:c451:: with SMTP id l17mr3551632wmi.127.1602681627926; Wed, 14 Oct 2020 06:20:27 -0700 (PDT) MIME-Version: 1.0 References: <20200930160917.1234225-1-hch@lst.de> <20200930160917.1234225-9-hch@lst.de> In-Reply-To: <20200930160917.1234225-9-hch@lst.de> From: Tomasz Figa Date: Wed, 14 Oct 2020 15:20:16 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 8/8] WIP: add a dma_alloc_contiguous API To: Christoph Hellwig Cc: Mauro Carvalho Chehab , Marek Szyprowski , "list@263.net:IOMMU DRIVERS , Joerg Roedel ," , Robin Murphy , Linux Doc Mailing List , Linux Kernel Mailing List , Linux Media Mailing List , ribalda@chromium.org Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org +CC Ricardo who will be looking into using this in the USB stack (UVC camera driver). On Wed, Sep 30, 2020 at 6:09 PM Christoph Hellwig wrote: > > Add a new API that returns a virtually non-contigous array of pages > and dma address. This API is only implemented for dma-iommu and will > not be implemented for non-iommu DMA API instances that have to allocate > contiguous memory. It is up to the caller to check if the API is > available. > > The intent is that media drivers can use this API if either: > > - no kernel mapping or only temporary kernel mappings are required. > That is as a better replacement for DMA_ATTR_NO_KERNEL_MAPPING > - a kernel mapping is required for cached and DMA mapped pages, but > the driver also needs the pages to e.g. map them to userspace. > In that sense it is a replacement for some aspects of the recently > removed and never fully implemented DMA_ATTR_NON_CONSISTENT > > Signed-off-by: Christoph Hellwig > --- > drivers/iommu/dma-iommu.c | 73 +++++++++++++++++++++++++------------ > include/linux/dma-mapping.h | 9 +++++ > kernel/dma/mapping.c | 35 ++++++++++++++++++ > 3 files changed, 93 insertions(+), 24 deletions(-) > > diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c > index 7922f545cd5eef..158026a856622c 100644 > --- a/drivers/iommu/dma-iommu.c > +++ b/drivers/iommu/dma-iommu.c > @@ -565,23 +565,12 @@ static struct page **__iommu_dma_alloc_pages(struct device *dev, > return pages; > } > > -/** > - * iommu_dma_alloc_remap - Allocate and map a buffer contiguous in IOVA space > - * @dev: Device to allocate memory for. Must be a real device > - * attached to an iommu_dma_domain > - * @size: Size of buffer in bytes > - * @dma_handle: Out argument for allocated DMA handle > - * @gfp: Allocation flags > - * @prot: pgprot_t to use for the remapped mapping > - * @attrs: DMA attributes for this allocation > - * > - * If @size is less than PAGE_SIZE, then a full CPU page will be allocated, > +/* > + * If size is less than PAGE_SIZE, then a full CPU page will be allocated, > * but an IOMMU which supports smaller pages might not map the whole thing. > - * > - * Return: Mapped virtual address, or NULL on failure. > */ > -static void *iommu_dma_alloc_remap(struct device *dev, size_t size, > - dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot, > +static struct page **__iommu_dma_alloc_noncontiguous(struct device *dev, > + size_t size, dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot, > unsigned long attrs) > { > struct iommu_domain *domain = iommu_get_dma_domain(dev); > @@ -593,7 +582,6 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size, > struct page **pages; > struct sg_table sgt; > dma_addr_t iova; > - void *vaddr; > > *dma_handle = DMA_MAPPING_ERROR; > > @@ -636,17 +624,10 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size, > < size) > goto out_free_sg; > > - vaddr = dma_common_pages_remap(pages, size, prot, > - __builtin_return_address(0)); > - if (!vaddr) > - goto out_unmap; > - > *dma_handle = iova; > sg_free_table(&sgt); > - return vaddr; > + return pages; > > -out_unmap: > - __iommu_dma_unmap(dev, iova, size); > out_free_sg: > sg_free_table(&sgt); > out_free_iova: > @@ -656,6 +637,46 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size, > return NULL; > } > > +static void *iommu_dma_alloc_remap(struct device *dev, size_t size, > + dma_addr_t *dma_handle, gfp_t gfp, pgprot_t prot, > + unsigned long attrs) > +{ > + struct page **pages; > + void *vaddr; > + > + pages = __iommu_dma_alloc_noncontiguous(dev, size, dma_handle, gfp, > + prot, attrs); > + if (!pages) > + return NULL; > + vaddr = dma_common_pages_remap(pages, size, prot, > + __builtin_return_address(0)); > + if (!vaddr) > + goto out_unmap; > + return vaddr; > + > +out_unmap: > + __iommu_dma_unmap(dev, *dma_handle, size); > + __iommu_dma_free_pages(pages, PAGE_ALIGN(size) >> PAGE_SHIFT); > + return NULL; > +} > + > +#ifdef CONFIG_DMA_REMAP > +static struct page **iommu_dma_alloc_noncontiguous(struct device *dev, > + size_t size, dma_addr_t *dma_handle, gfp_t gfp, > + unsigned long attrs) > +{ > + return __iommu_dma_alloc_noncontiguous(dev, size, dma_handle, gfp, > + PAGE_KERNEL, attrs); > +} > + > +static void iommu_dma_free_noncontiguous(struct device *dev, size_t size, > + struct page **pages, dma_addr_t dma_handle) > +{ > + __iommu_dma_unmap(dev, dma_handle, size); > + __iommu_dma_free_pages(pages, PAGE_ALIGN(size) >> PAGE_SHIFT); > +} > +#endif > + > static void iommu_dma_sync_single_for_cpu(struct device *dev, > dma_addr_t dma_handle, size_t size, enum dma_data_direction dir) > { > @@ -1110,6 +1131,10 @@ static const struct dma_map_ops iommu_dma_ops = { > .free = iommu_dma_free, > .alloc_pages = dma_common_alloc_pages, > .free_pages = dma_common_free_pages, > +#ifdef CONFIG_DMA_REMAP > + .alloc_noncontiguous = iommu_dma_alloc_noncontiguous, > + .free_noncontiguous = iommu_dma_free_noncontiguous, > +#endif > .mmap = iommu_dma_mmap, > .get_sgtable = iommu_dma_get_sgtable, > .map_page = iommu_dma_map_page, > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 4b9b1d64f5ec9e..51bbc32365bb8d 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -74,6 +74,10 @@ struct dma_map_ops { > gfp_t gfp); > void (*free_pages)(struct device *dev, size_t size, struct page *vaddr, > dma_addr_t dma_handle, enum dma_data_direction dir); > + struct page **(*alloc_noncontiguous)(struct device *dev, size_t size, > + dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs); > + void (*free_noncontiguous)(struct device *dev, size_t size, > + struct page **pages, dma_addr_t dma_handle); > int (*mmap)(struct device *, struct vm_area_struct *, > void *, dma_addr_t, size_t, > unsigned long attrs); > @@ -384,6 +388,11 @@ void *dma_alloc_noncoherent(struct device *dev, size_t size, > dma_addr_t *dma_handle, enum dma_data_direction dir, gfp_t gfp); > void dma_free_noncoherent(struct device *dev, size_t size, void *vaddr, > dma_addr_t dma_handle, enum dma_data_direction dir); > +bool dma_can_alloc_noncontiguous(struct device *dev); > +struct page **dma_alloc_noncontiguous(struct device *dev, size_t size, > + dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs); > +void dma_free_noncontiguous(struct device *dev, size_t size, > + struct page **pages, dma_addr_t dma_handle); > > static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr, > size_t size, enum dma_data_direction dir, unsigned long attrs) > diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c > index 06115f59f4ffbf..6d975d1a20dd72 100644 > --- a/kernel/dma/mapping.c > +++ b/kernel/dma/mapping.c > @@ -529,6 +529,41 @@ void dma_free_noncoherent(struct device *dev, size_t size, void *vaddr, > } > EXPORT_SYMBOL_GPL(dma_free_noncoherent); > > +bool dma_can_alloc_noncontiguous(struct device *dev) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + > + return ops && ops->free_noncontiguous; > +} > +EXPORT_SYMBOL_GPL(dma_can_alloc_noncontiguous); > + > +struct page **dma_alloc_noncontiguous(struct device *dev, size_t size, > + dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + > + if (WARN_ON_ONCE(!dma_can_alloc_noncontiguous(dev))) > + return NULL; > + if (attrs & ~DMA_ATTR_ALLOC_SINGLE_PAGES) { > + dev_warn(dev, "invalid flags (0x%lx) for %s\n", > + attrs, __func__); > + return NULL; > + } > + return ops->alloc_noncontiguous(dev, size, dma_handle, gfp, attrs); > +} > +EXPORT_SYMBOL_GPL(dma_alloc_noncontiguous); > + > +void dma_free_noncontiguous(struct device *dev, size_t size, > + struct page **pages, dma_addr_t dma_handle) > +{ > + const struct dma_map_ops *ops = get_dma_ops(dev); > + > + if (WARN_ON_ONCE(!dma_can_alloc_noncontiguous(dev))) > + return; > + ops->free_noncontiguous(dev, size, pages, dma_handle); > +} > +EXPORT_SYMBOL_GPL(dma_free_noncontiguous); > + > int dma_supported(struct device *dev, u64 mask) > { > const struct dma_map_ops *ops = get_dma_ops(dev); > -- > 2.28.0 >