| Message ID | 20200505084614.30424-1-m.szyprowski@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | DRM: fix struct sg_table nents vs. orig_nents misuse | expand |
Hi Christoph, On 05.05.2020 12:22, Christoph Hellwig wrote: >> +static inline int dma_map_sgtable_attrs(struct device *dev, >> + struct sg_table *sgt, enum dma_data_direction dir, unsigned long attrs) > Two tab indents for parameter continuation, please. > > Can we also skip the separate _attrs version? The existing ones have the > separate _attrs variant as there were pre-existing versions without the > attrs argument and lots of users, but that doesn't really apply here as > an extra 0 argument isn't really an issue. Okay. >> +static inline size_t iommu_map_sgtable(struct iommu_domain *domain, >> + unsigned long iova, struct sg_table *sgt, int prot) >> +{ >> + return iommu_map_sg(domain, iova, sgt->sgl, sgt->orig_nents, prot); >> +} > Should this be a separate patch due to the different subsystems? > > FYI, I'll happily pick up the prep patches in an immutable branch of > the dma-mapping tree one we have settled on the details. Okay. Best regards
Hi Marek, On 05/05/2020 10:45, Marek Szyprowski wrote: > struct sg_table is a common structure used for describing a memory > buffer. It consists of a scatterlist with memory pages and DMA addresses > (sgl entry), as well as the number of scatterlist entries: CPU pages > (orig_nents entry) and DMA pages (nents entry). > > It turned out that it was a common mistake to misuse nents and orig_nents > entries, call dma-mapping functions with a wrong number of entries or > ignoring the number of mapped entries returned by the dma_map_sg > function. > > To avoid such issues, lets introduce a common wrappers operating directly > on the struct sg_table objects, which take care of the proper use of > the nents and orig_nents entries. > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> > --- > include/linux/dma-mapping.h | 32 ++++++++++++++++++++++++++++++++ > include/linux/iommu.h | 6 ++++++ > 2 files changed, 38 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index b43116a..8364c20d 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -609,6 +609,36 @@ static inline void dma_sync_single_range_for_device(struct device *dev, > return dma_sync_single_for_device(dev, addr + offset, size, dir); > } > > +static inline int dma_map_sgtable_attrs(struct device *dev, > + struct sg_table *sgt, enum dma_data_direction dir, unsigned long attrs) Please document these new inline functions! The core reason IMHO why so many drivers do this wrong is that the struct sg_table documentation is very poor. In particular w.r.t. how the nents and orig_nents fields should be used. It confused me, and clearly I am not alone in that. So while this is a very nice improvement, it doesn't address the core issue, i.e. the documentation. Especially some examples on how to use these new functions would be welcome. Regards, Hans > +{ > + int n = dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs); > + > + if (n > 0) { > + sgt->nents = n; > + return 0; > + } > + return -EINVAL; > +} > + > +static inline void dma_unmap_sgtable_attrs(struct device *dev, > + struct sg_table *sgt, enum dma_data_direction dir, unsigned long attrs) > +{ > + dma_unmap_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs); > +} > + > +static inline void dma_sync_sgtable_for_cpu(struct device *dev, > + struct sg_table *sgt, enum dma_data_direction dir) > +{ > + dma_sync_sg_for_cpu(dev, sgt->sgl, sgt->orig_nents, dir); > +} > + > +static inline void dma_sync_sgtable_for_device(struct device *dev, > + struct sg_table *sgt, enum dma_data_direction dir) > +{ > + dma_sync_sg_for_device(dev, sgt->sgl, sgt->orig_nents, dir); > +} > + > #define dma_map_single(d, a, s, r) dma_map_single_attrs(d, a, s, r, 0) > #define dma_unmap_single(d, a, s, r) dma_unmap_single_attrs(d, a, s, r, 0) > #define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, 0) > @@ -617,6 +647,8 @@ static inline void dma_sync_single_range_for_device(struct device *dev, > #define dma_unmap_page(d, a, s, r) dma_unmap_page_attrs(d, a, s, r, 0) > #define dma_get_sgtable(d, t, v, h, s) dma_get_sgtable_attrs(d, t, v, h, s, 0) > #define dma_mmap_coherent(d, v, c, h, s) dma_mmap_attrs(d, v, c, h, s, 0) > +#define dma_map_sgtable(d, s, r) dma_map_sgtable_attrs(d, s, r, 0) > +#define dma_unmap_sgtable(d, s, r) dma_unmap_sgtable_attrs(d, s, r, 0) > > extern int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, > void *cpu_addr, dma_addr_t dma_addr, size_t size, > diff --git a/include/linux/iommu.h b/include/linux/iommu.h > index 7ef8b0b..5106b65 100644 > --- a/include/linux/iommu.h > +++ b/include/linux/iommu.h > @@ -466,6 +466,12 @@ extern size_t iommu_map_sg_atomic(struct iommu_domain *domain, > extern void iommu_set_fault_handler(struct iommu_domain *domain, > iommu_fault_handler_t handler, void *token); > > +static inline size_t iommu_map_sgtable(struct iommu_domain *domain, > + unsigned long iova, struct sg_table *sgt, int prot) > +{ > + return iommu_map_sg(domain, iova, sgt->sgl, sgt->orig_nents, prot); > +} > + > extern void iommu_get_resv_regions(struct device *dev, struct list_head *list); > extern void iommu_put_resv_regions(struct device *dev, struct list_head *list); > extern void generic_iommu_put_resv_regions(struct device *dev, >
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index b43116a..8364c20d 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -609,6 +609,36 @@ static inline void dma_sync_single_range_for_device(struct device *dev, return dma_sync_single_for_device(dev, addr + offset, size, dir); } +static inline int dma_map_sgtable_attrs(struct device *dev, + struct sg_table *sgt, enum dma_data_direction dir, unsigned long attrs) +{ + int n = dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs); + + if (n > 0) { + sgt->nents = n; + return 0; + } + return -EINVAL; +} + +static inline void dma_unmap_sgtable_attrs(struct device *dev, + struct sg_table *sgt, enum dma_data_direction dir, unsigned long attrs) +{ + dma_unmap_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs); +} + +static inline void dma_sync_sgtable_for_cpu(struct device *dev, + struct sg_table *sgt, enum dma_data_direction dir) +{ + dma_sync_sg_for_cpu(dev, sgt->sgl, sgt->orig_nents, dir); +} + +static inline void dma_sync_sgtable_for_device(struct device *dev, + struct sg_table *sgt, enum dma_data_direction dir) +{ + dma_sync_sg_for_device(dev, sgt->sgl, sgt->orig_nents, dir); +} + #define dma_map_single(d, a, s, r) dma_map_single_attrs(d, a, s, r, 0) #define dma_unmap_single(d, a, s, r) dma_unmap_single_attrs(d, a, s, r, 0) #define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, 0) @@ -617,6 +647,8 @@ static inline void dma_sync_single_range_for_device(struct device *dev, #define dma_unmap_page(d, a, s, r) dma_unmap_page_attrs(d, a, s, r, 0) #define dma_get_sgtable(d, t, v, h, s) dma_get_sgtable_attrs(d, t, v, h, s, 0) #define dma_mmap_coherent(d, v, c, h, s) dma_mmap_attrs(d, v, c, h, s, 0) +#define dma_map_sgtable(d, s, r) dma_map_sgtable_attrs(d, s, r, 0) +#define dma_unmap_sgtable(d, s, r) dma_unmap_sgtable_attrs(d, s, r, 0) extern int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr, size_t size, diff --git a/include/linux/iommu.h b/include/linux/iommu.h index 7ef8b0b..5106b65 100644 --- a/include/linux/iommu.h +++ b/include/linux/iommu.h @@ -466,6 +466,12 @@ extern size_t iommu_map_sg_atomic(struct iommu_domain *domain, extern void iommu_set_fault_handler(struct iommu_domain *domain, iommu_fault_handler_t handler, void *token); +static inline size_t iommu_map_sgtable(struct iommu_domain *domain, + unsigned long iova, struct sg_table *sgt, int prot) +{ + return iommu_map_sg(domain, iova, sgt->sgl, sgt->orig_nents, prot); +} + extern void iommu_get_resv_regions(struct device *dev, struct list_head *list); extern void iommu_put_resv_regions(struct device *dev, struct list_head *list); extern void generic_iommu_put_resv_regions(struct device *dev,
struct sg_table is a common structure used for describing a memory buffer. It consists of a scatterlist with memory pages and DMA addresses (sgl entry), as well as the number of scatterlist entries: CPU pages (orig_nents entry) and DMA pages (nents entry). It turned out that it was a common mistake to misuse nents and orig_nents entries, call dma-mapping functions with a wrong number of entries or ignoring the number of mapped entries returned by the dma_map_sg function. To avoid such issues, lets introduce a common wrappers operating directly on the struct sg_table objects, which take care of the proper use of the nents and orig_nents entries. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- include/linux/dma-mapping.h | 32 ++++++++++++++++++++++++++++++++ include/linux/iommu.h | 6 ++++++ 2 files changed, 38 insertions(+)