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xen/gntdev: Allow mappings for DMA buffers
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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 <[email protected]>
Reviewed-by: Boris Ostrovsky <[email protected]>
Signed-off-by: Boris Ostrovsky <[email protected]>
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Oleksandr Andrushchenko authored and Boris Ostrovsky committed Jul 27, 2018
1 parent 9bdc730 commit 975ef7f
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Showing 2 changed files with 112 additions and 2 deletions.
99 changes: 97 additions & 2 deletions drivers/xen/gntdev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand Down Expand Up @@ -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 {
Expand All @@ -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,
Expand All @@ -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);
Expand All @@ -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;
Expand All @@ -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;

Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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, true);
#endif
pr_debug("priv %p\n", priv);

return 0;
Expand Down Expand Up @@ -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;

Expand Down
15 changes: 15 additions & 0 deletions include/uapi/xen/gntdev.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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__ */

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