Messages in this thread | | | Subject | Re: [Xen-devel] [PATCH v2 5/9] xen/gntdev: Allow mappings for DMA buffers | From | Oleksandr Andrushchenko <> | Date | Wed, 6 Jun 2018 11:14:12 +0300 |
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On 06/04/2018 11:12 PM, Boris Ostrovsky wrote: > On 06/01/2018 07:41 AM, Oleksandr Andrushchenko wrote: >> From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> >> >> Allow mappings for DMA backed buffers if grant table module >> supports such: this extends grant device to not only map buffers >> made of balloon pages, but also from buffers allocated with >> dma_alloc_xxx. >> >> Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com> >> --- >> drivers/xen/gntdev.c | 99 ++++++++++++++++++++++++++++++++++++++- >> include/uapi/xen/gntdev.h | 15 ++++++ >> 2 files changed, 112 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c >> index bd56653b9bbc..9813fc440c70 100644 >> --- a/drivers/xen/gntdev.c >> +++ b/drivers/xen/gntdev.c >> @@ -37,6 +37,9 @@ >> #include <linux/slab.h> >> #include <linux/highmem.h> >> #include <linux/refcount.h> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> +#include <linux/of_device.h> >> +#endif >> >> #include <xen/xen.h> >> #include <xen/grant_table.h> >> @@ -72,6 +75,11 @@ struct gntdev_priv { >> struct mutex lock; >> struct mm_struct *mm; >> struct mmu_notifier mn; >> + >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + /* Device for which DMA memory is allocated. */ >> + struct device *dma_dev; >> +#endif >> }; >> >> struct unmap_notify { >> @@ -96,10 +104,27 @@ struct grant_map { >> struct gnttab_unmap_grant_ref *kunmap_ops; >> struct page **pages; >> unsigned long pages_vm_start; >> + >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + /* >> + * If dmabuf_vaddr is not NULL then this mapping is backed by DMA >> + * capable memory. >> + */ >> + >> + struct device *dma_dev; >> + /* Flags used to create this DMA buffer: GNTDEV_DMA_FLAG_XXX. */ >> + int dma_flags; >> + void *dma_vaddr; >> + dma_addr_t dma_bus_addr; >> + /* This is required for gnttab_dma_{alloc|free}_pages. */ > How about > > /* Needed to avoid allocation in gnttab_dma_free_pages(). */ > Ok >> + xen_pfn_t *frames; >> +#endif >> }; >> >> static int unmap_grant_pages(struct grant_map *map, int offset, int pages); >> >> +static struct miscdevice gntdev_miscdev; >> + >> /* ------------------------------------------------------------------ */ >> >> static void gntdev_print_maps(struct gntdev_priv *priv, >> @@ -121,8 +146,27 @@ static void gntdev_free_map(struct grant_map *map) >> if (map == NULL) >> return; >> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + if (map->dma_vaddr) { >> + struct gnttab_dma_alloc_args args; >> + >> + args.dev = map->dma_dev; >> + args.coherent = map->dma_flags & GNTDEV_DMA_FLAG_COHERENT; >> + args.nr_pages = map->count; >> + args.pages = map->pages; >> + args.frames = map->frames; >> + args.vaddr = map->dma_vaddr; >> + args.dev_bus_addr = map->dma_bus_addr; >> + >> + gnttab_dma_free_pages(&args); >> + } else >> +#endif >> if (map->pages) >> gnttab_free_pages(map->count, map->pages); >> + >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + kfree(map->frames); >> +#endif > > Can this be done under if (map->dma_vaddr) ?
> In other words, is it > possible for dma_vaddr to be NULL and still have unallocated frames pointer? It is possible to have vaddr == NULL and frames != NULL as we allocate frames outside of gnttab_dma_alloc_pages which may fail. Calling kfree on NULL pointer is safe, so I see no reason to change this code. > >> kfree(map->pages); >> kfree(map->grants); >> kfree(map->map_ops); >> @@ -132,7 +176,8 @@ static void gntdev_free_map(struct grant_map *map) >> kfree(map); >> } >> >> -static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count) >> +static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count, >> + int dma_flags) >> { >> struct grant_map *add; >> int i; >> @@ -155,6 +200,37 @@ static struct grant_map *gntdev_alloc_map(struct gntdev_priv *priv, int count) >> NULL == add->pages) >> goto err; >> >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + add->dma_flags = dma_flags; >> + >> + /* >> + * Check if this mapping is requested to be backed >> + * by a DMA buffer. >> + */ >> + if (dma_flags & (GNTDEV_DMA_FLAG_WC | GNTDEV_DMA_FLAG_COHERENT)) { >> + struct gnttab_dma_alloc_args args; >> + >> + add->frames = kcalloc(count, sizeof(add->frames[0]), >> + GFP_KERNEL); >> + if (!add->frames) >> + goto err; >> + >> + /* Remember the device, so we can free DMA memory. */ >> + add->dma_dev = priv->dma_dev; >> + >> + args.dev = priv->dma_dev; >> + args.coherent = dma_flags & GNTDEV_DMA_FLAG_COHERENT; >> + args.nr_pages = count; >> + args.pages = add->pages; >> + args.frames = add->frames; >> + >> + if (gnttab_dma_alloc_pages(&args)) >> + goto err; >> + >> + add->dma_vaddr = args.vaddr; >> + add->dma_bus_addr = args.dev_bus_addr; >> + } else >> +#endif >> if (gnttab_alloc_pages(count, add->pages)) >> goto err; >> >> @@ -325,6 +401,14 @@ static int map_grant_pages(struct grant_map *map) >> map->unmap_ops[i].handle = map->map_ops[i].handle; >> if (use_ptemod) >> map->kunmap_ops[i].handle = map->kmap_ops[i].handle; >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + else if (map->dma_vaddr) { >> + unsigned long mfn; >> + >> + mfn = __pfn_to_mfn(page_to_pfn(map->pages[i])); > > Not pfn_to_mfn()? I'd love to, but pfn_to_mfn is only defined for x86, not ARM: [1] and [2] Thus,
drivers/xen/gntdev.c:408:10: error: implicit declaration of function ‘pfn_to_mfn’ [-Werror=implicit-function-declaration] mfn = pfn_to_mfn(page_to_pfn(map->pages[i]));
So, I'll keep __pfn_to_mfn > > > -boris Thank you, Oleksandr >> + map->unmap_ops[i].dev_bus_addr = __pfn_to_phys(mfn); >> + } >> +#endif >> } >> return err; >> } >> @@ -548,6 +632,17 @@ static int gntdev_open(struct inode *inode, struct file *flip) >> } >> >> flip->private_data = priv; >> +#ifdef CONFIG_XEN_GRANT_DMA_ALLOC >> + priv->dma_dev = gntdev_miscdev.this_device; >> + >> + /* >> + * The device is not spawn from a device tree, so arch_setup_dma_ops >> + * is not called, thus leaving the device with dummy DMA ops. >> + * Fix this call of_dma_configure() with a NULL node to set >> + * default DMA ops. >> + */ >> + of_dma_configure(priv->dma_dev, NULL); >> +#endif >> pr_debug("priv %p\n", priv); >> >> return 0; >> @@ -589,7 +684,7 @@ static long gntdev_ioctl_map_grant_ref(struct gntdev_priv *priv, >> return -EINVAL; >> >> err = -ENOMEM; >> - map = gntdev_alloc_map(priv, op.count); >> + map = gntdev_alloc_map(priv, op.count, 0 /* This is not a dma-buf. */); >> if (!map) >> return err; >> >> diff --git a/include/uapi/xen/gntdev.h b/include/uapi/xen/gntdev.h >> index 6d1163456c03..4b9d498a31d4 100644 >> --- a/include/uapi/xen/gntdev.h >> +++ b/include/uapi/xen/gntdev.h >> @@ -200,4 +200,19 @@ struct ioctl_gntdev_grant_copy { >> /* Send an interrupt on the indicated event channel */ >> #define UNMAP_NOTIFY_SEND_EVENT 0x2 >> >> +/* >> + * Flags to be used while requesting memory mapping's backing storage >> + * to be allocated with DMA API. >> + */ >> + >> +/* >> + * The buffer is backed with memory allocated with dma_alloc_wc. >> + */ >> +#define GNTDEV_DMA_FLAG_WC (1 << 0) >> + >> +/* >> + * The buffer is backed with memory allocated with dma_alloc_coherent. >> + */ >> +#define GNTDEV_DMA_FLAG_COHERENT (1 << 1) >> + >> #endif /* __LINUX_PUBLIC_GNTDEV_H__ */ > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xenproject.org > https://lists.xenproject.org/mailman/listinfo/xen-devel [1] https://elixir.bootlin.com/linux/v4.17/ident/pfn_to_mfn [2] https://elixir.bootlin.com/linux/v4.17/ident/__pfn_to_mfn
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