Re: [PATCH v4 5/9] xen/gntdev: Allow mappings for DMA buffers

Please note, that this will need a change (attached) while applying to the mainline kernel because of API changes [1].

Unfortunately, current Xen tip kernel tree is v4.17-rc5 based, so I cannot make the change in this patch now.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...

On 06/15/2018 09:27 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 Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.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..0ec670d1d4e7 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;
• /* Needed to avoid allocation in gnttab_dma_free_pages(). */
• 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 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 bfn;
  

• 	bfn = pfn_to_bfn(page_to_pfn(map->pages[i]));
  

• 	map->unmap_ops[i].dev_bus_addr = __pfn_to_phys(bfn);
  

• }
  

+#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 by calling 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__ */