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Re: [Xen-devel] [PATCH v2 5/9] xen/gntdev: Allow mappings for DMA buffers
- To: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, dri-devel@xxxxxxxxxxxxxxxxxxxxx, linux-media@xxxxxxxxxxxxxxx, jgross@xxxxxxxx, konrad.wilk@xxxxxxxxxx
- From: Oleksandr Andrushchenko <andr2000@xxxxxxxxx>
- Date: Wed, 6 Jun 2018 11:14:12 +0300
- Cc: daniel.vetter@xxxxxxxxx, matthew.d.roper@xxxxxxxxx, dongwon.kim@xxxxxxxxx, Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
- Delivery-date: Wed, 06 Jun 2018 08:14:32 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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@xxxxxxxx>
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@xxxxxxxx>
---
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__ */
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[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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