Messages in this thread | | | Subject | Re: [PATCH v5 14/16] dma-direct: Allocate memory from restricted DMA pool if available | From | Robin Murphy <> | Date | Fri, 23 Apr 2021 14:46:25 +0100 |
| |
On 2021-04-22 09:15, Claire Chang wrote: > The restricted DMA pool is preferred if available. > > The restricted DMA pools provide a basic level of protection against the > DMA overwriting buffer contents at unexpected times. However, to protect > against general data leakage and system memory corruption, the system > needs to provide a way to lock down the memory access, e.g., MPU. > > Signed-off-by: Claire Chang <tientzu@chromium.org> > --- > kernel/dma/direct.c | 35 ++++++++++++++++++++++++++--------- > 1 file changed, 26 insertions(+), 9 deletions(-) > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 7a27f0510fcc..29523d2a9845 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -78,6 +78,10 @@ static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) > static void __dma_direct_free_pages(struct device *dev, struct page *page, > size_t size) > { > +#ifdef CONFIG_DMA_RESTRICTED_POOL > + if (swiotlb_free(dev, page, size)) > + return; > +#endif > dma_free_contiguous(dev, page, size); > } > > @@ -92,7 +96,17 @@ static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size, > > gfp |= dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask, > &phys_limit); > - page = dma_alloc_contiguous(dev, size, gfp); > + > +#ifdef CONFIG_DMA_RESTRICTED_POOL > + page = swiotlb_alloc(dev, size); > + if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { > + __dma_direct_free_pages(dev, page, size); > + page = NULL; > + } > +#endif > + > + if (!page) > + page = dma_alloc_contiguous(dev, size, gfp); > if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) { > dma_free_contiguous(dev, page, size); > page = NULL; > @@ -148,7 +162,7 @@ void *dma_direct_alloc(struct device *dev, size_t size, > gfp |= __GFP_NOWARN; > > if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && > - !force_dma_unencrypted(dev)) { > + !force_dma_unencrypted(dev) && !is_dev_swiotlb_force(dev)) { > page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO); > if (!page) > return NULL; > @@ -161,8 +175,8 @@ void *dma_direct_alloc(struct device *dev, size_t size, > } > > if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && > - !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && > - !dev_is_dma_coherent(dev)) > + !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !dev_is_dma_coherent(dev) && > + !is_dev_swiotlb_force(dev)) > return arch_dma_alloc(dev, size, dma_handle, gfp, attrs); > > /* > @@ -172,7 +186,9 @@ void *dma_direct_alloc(struct device *dev, size_t size, > if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) && > !gfpflags_allow_blocking(gfp) && > (force_dma_unencrypted(dev) || > - (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !dev_is_dma_coherent(dev)))) > + (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && > + !dev_is_dma_coherent(dev))) && > + !is_dev_swiotlb_force(dev)) > return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp); > > /* we always manually zero the memory once we are done */ > @@ -253,15 +269,15 @@ void dma_direct_free(struct device *dev, size_t size, > unsigned int page_order = get_order(size); > > if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) && > - !force_dma_unencrypted(dev)) { > + !force_dma_unencrypted(dev) && !is_dev_swiotlb_force(dev)) { > /* cpu_addr is a struct page cookie, not a kernel address */ > dma_free_contiguous(dev, cpu_addr, size); > return; > } > > if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) && > - !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && > - !dev_is_dma_coherent(dev)) { > + !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !dev_is_dma_coherent(dev) && > + !is_dev_swiotlb_force(dev)) { > arch_dma_free(dev, size, cpu_addr, dma_addr, attrs); > return; > } > @@ -289,7 +305,8 @@ struct page *dma_direct_alloc_pages(struct device *dev, size_t size, > void *ret; > > if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) && > - force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp)) > + force_dma_unencrypted(dev) && !gfpflags_allow_blocking(gfp) && > + !is_dev_swiotlb_force(dev)) > return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);
Wait, this seems broken for non-coherent devices - in that case we need to return a non-cacheable address, but we can't simply fall through into the remapping path below in GFP_ATOMIC context. That's why we need the atomic pool concept in the first place :/
Unless I've overlooked something, we're still using the regular cacheable linear map address of the dma_io_tlb_mem buffer, no?
Robin.
> > page = __dma_direct_alloc_pages(dev, size, gfp); >
| |