On 05/25/2018 11:33 AM, Oleksandr Andrushchenko wrote: > From: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com> > > Extend grant table module API to allow allocating buffers that can > be used for DMA operations and mapping foreign grant references > on top of those. > The resulting buffer is similar to the one allocated by the balloon > driver in terms that proper memory reservation is made > ({increase|decrease}_reservation and VA mappings updated if needed). > This is useful for sharing foreign buffers with HW drivers which > cannot work with scattered buffers provided by the balloon driver, > but require DMAable memory instead. > > Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushche...@epam.com> > --- > drivers/xen/Kconfig | 13 ++++ > drivers/xen/grant-table.c | 124 ++++++++++++++++++++++++++++++++++++++ > include/xen/grant_table.h | 25 ++++++++ > 3 files changed, 162 insertions(+) > > diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig > index e5d0c28372ea..3431fe210624 100644 > --- a/drivers/xen/Kconfig > +++ b/drivers/xen/Kconfig > @@ -161,6 +161,19 @@ config XEN_GRANT_DEV_ALLOC > to other domains. This can be used to implement frontend drivers > or as part of an inter-domain shared memory channel. > > +config XEN_GRANT_DMA_ALLOC > + bool "Allow allocating DMA capable buffers with grant reference module" > + depends on XEN
Should it depend on anything from DMA? CONFIG_HAS_DMA for example? > + help > + Extends grant table module API to allow allocating DMA capable > + buffers and mapping foreign grant references on top of it. > + The resulting buffer is similar to one allocated by the balloon > + driver in terms that proper memory reservation is made > + ({increase|decrease}_reservation and VA mappings updated if needed). > + This is useful for sharing foreign buffers with HW drivers which > + cannot work with scattered buffers provided by the balloon driver, > + but require DMAable memory instead. > + > config SWIOTLB_XEN > def_bool y > select SWIOTLB > diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c > index d7488226e1f2..06fe6e7f639c 100644 > --- a/drivers/xen/grant-table.c > +++ b/drivers/xen/grant-table.c > @@ -45,6 +45,9 @@ > #include <linux/workqueue.h> > #include <linux/ratelimit.h> > #include <linux/moduleparam.h> > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +#include <linux/dma-mapping.h> > +#endif > > #include <xen/xen.h> > #include <xen/interface/xen.h> > @@ -57,6 +60,7 @@ > #ifdef CONFIG_X86 > #include <asm/xen/cpuid.h> > #endif > +#include <xen/mem_reservation.h> > #include <asm/xen/hypercall.h> > #include <asm/xen/interface.h> > > @@ -811,6 +815,82 @@ int gnttab_alloc_pages(int nr_pages, struct page **pages) > } > EXPORT_SYMBOL(gnttab_alloc_pages); > > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +/** > + * gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping > into > + * @args: arguments to the function > + */ > +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args) > +{ > + unsigned long pfn, start_pfn; > + xen_pfn_t *frames; > + size_t size; > + int i, ret; > + > + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); > + if (!frames) > + return -ENOMEM; > + > + size = args->nr_pages << PAGE_SHIFT; > + if (args->coherent) > + args->vaddr = dma_alloc_coherent(args->dev, size, > + &args->dev_bus_addr, > + GFP_KERNEL | __GFP_NOWARN); > + else > + args->vaddr = dma_alloc_wc(args->dev, size, > + &args->dev_bus_addr, > + GFP_KERNEL | __GFP_NOWARN); > + if (!args->vaddr) { > + pr_err("Failed to allocate DMA buffer of size %zu\n", size); > + ret = -ENOMEM; > + goto fail_free_frames; > + } > + > + start_pfn = __phys_to_pfn(args->dev_bus_addr); > + for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages; > + pfn++, i++) { > + struct page *page = pfn_to_page(pfn); > + > + args->pages[i] = page; > + frames[i] = xen_page_to_gfn(page); > + xenmem_reservation_scrub_page(page); > + } > + > + xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages); > + > + ret = xenmem_reservation_decrease(args->nr_pages, frames); > + if (ret != args->nr_pages) { > + pr_err("Failed to decrease reservation for DMA buffer\n"); > + xenmem_reservation_increase(ret, frames); > + ret = -EFAULT; > + goto fail_free_dma; > + } > + > + ret = gnttab_pages_set_private(args->nr_pages, args->pages); > + if (ret < 0) > + goto fail_clear_private; > + > + kfree(frames); > + return 0; > + > +fail_clear_private: > + gnttab_pages_clear_private(args->nr_pages, args->pages); > +fail_free_dma: Do you need to xenmem_reservation_increase()? > + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, > + frames); > + if (args->coherent) > + dma_free_coherent(args->dev, size, > + args->vaddr, args->dev_bus_addr); > + else > + dma_free_wc(args->dev, size, > + args->vaddr, args->dev_bus_addr); > +fail_free_frames: > + kfree(frames); > + return ret; > +} > +EXPORT_SYMBOL(gnttab_dma_alloc_pages); > +#endif > + > void gnttab_pages_clear_private(int nr_pages, struct page **pages) > { > int i; > @@ -838,6 +918,50 @@ void gnttab_free_pages(int nr_pages, struct page **pages) > } > EXPORT_SYMBOL(gnttab_free_pages); > > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +/** > + * gnttab_dma_free_pages - free DMAable pages > + * @args: arguments to the function > + */ > +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args) > +{ > + xen_pfn_t *frames; > + size_t size; > + int i, ret; > + > + gnttab_pages_clear_private(args->nr_pages, args->pages); > + > + frames = kcalloc(args->nr_pages, sizeof(*frames), GFP_KERNEL); Any way you can do it without allocating memory? One possibility is to keep allocated frames from gnttab_dma_alloc_pages(). (Not sure I like that either but it's the only thing I can think of). > + if (!frames) > + return -ENOMEM; > + > + for (i = 0; i < args->nr_pages; i++) > + frames[i] = page_to_xen_pfn(args->pages[i]); Not xen_page_to_gfn()? > + > + ret = xenmem_reservation_increase(args->nr_pages, frames); > + if (ret != args->nr_pages) { > + pr_err("Failed to decrease reservation for DMA buffer\n"); > + ret = -EFAULT; > + } else { > + ret = 0; > + } > + > + xenmem_reservation_va_mapping_update(args->nr_pages, args->pages, > + frames); > + > + size = args->nr_pages << PAGE_SHIFT; > + if (args->coherent) > + dma_free_coherent(args->dev, size, > + args->vaddr, args->dev_bus_addr); > + else > + dma_free_wc(args->dev, size, > + args->vaddr, args->dev_bus_addr); > + kfree(frames); > + return ret; > +} > +EXPORT_SYMBOL(gnttab_dma_free_pages); > +#endif > + > /* Handling of paged out grant targets (GNTST_eagain) */ > #define MAX_DELAY 256 > static inline void > diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h > index de03f2542bb7..982e34242b9c 100644 > --- a/include/xen/grant_table.h > +++ b/include/xen/grant_table.h > @@ -198,6 +198,31 @@ void gnttab_free_auto_xlat_frames(void); > int gnttab_alloc_pages(int nr_pages, struct page **pages); > void gnttab_free_pages(int nr_pages, struct page **pages); > > +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC > +struct gnttab_dma_alloc_args { > + /* Device for which DMA memory will be/was allocated. */ > + struct device *dev; > + /* > + * If set then DMA buffer is coherent and write-combine otherwise. > + */ Single-line comment > + bool coherent; > + /* > + * Number of entries in the @pages array, defines the size > + * of the DMA buffer. > + */ This can be made into single line comment as well. However, I am not sure this comment as well as those below are necessary. Fields names are self-describing IMO. -boris > + int nr_pages; > + /* Array of pages @pages filled with pages of the DMA buffer. */ > + struct page **pages; > + /* Virtual/CPU address of the DMA buffer. */ > + void *vaddr; > + /* Bus address of the DMA buffer. */ > + dma_addr_t dev_bus_addr; > +}; > + > +int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args); > +int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args); > +#endif > + > int gnttab_pages_set_private(int nr_pages, struct page **pages); > void gnttab_pages_clear_private(int nr_pages, struct page **pages); > _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel