[PATCH RFC 10/26] drm/xe/dma-buf: Use the SGT mapping type

Jason Gunthorpe
2026-02-18T00:12:19Z

Like habana, xe wants to check pci_p2pdma_distance(), but unlike
habana, it can migrate to system memory and support non-p2p DMAs as well.

Add two exporter SGT mapping types, one that matches P2P and one that
matches all of the non-p2p. The pin and map code will force migrate if
the non-p2p one is matched.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/gpu/drm/xe/xe_dma_buf.c | 58 +++++++++++++++++++++------------
1 file changed, 37 insertions(+), 21 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c
index 7c74a31d448602..9968f37657d57d 100644
--- a/drivers/gpu/drm/xe/xe_dma_buf.c
+++ b/drivers/gpu/drm/xe/xe_dma_buf.c
@@ -7,7 +7,7 @@

#include <kunit/test.h>
#include <linux/dma-buf.h>
-#include <linux/pci-p2pdma.h>
+#include <linux/dma-buf-mapping.h>

#include <drm/drm_device.h>
#include <drm/drm_prime.h>
@@ -27,13 +27,6 @@ static int xe_dma_buf_attach(struct dma_buf *dmabuf,
{
struct drm_gem_object *obj = attach->dmabuf->priv;

- if (attach->peer2peer &&
- pci_p2pdma_distance(to_pci_dev(obj->dev->dev), attach->dev, false) < 0)
- attach->peer2peer = false;
-
- if (!attach->peer2peer && !xe_bo_can_migrate(gem_to_xe_bo(obj), XE_PL_TT))
- return -EOPNOTSUPP;
-
xe_pm_runtime_get(to_xe_device(obj->dev));
return 0;
}
@@ -53,14 +46,12 @@ static int xe_dma_buf_pin(struct dma_buf_attachment *attach)
struct xe_bo *bo = gem_to_xe_bo(obj);
struct xe_device *xe = xe_bo_device(bo);
struct drm_exec *exec = XE_VALIDATION_UNSUPPORTED;
- bool allow_vram = true;
+ bool allow_vram = dma_buf_sgt_p2p_allowed(attach);
int ret;

- if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {
- allow_vram = false;
- } else {
+ if (allow_vram) {
list_for_each_entry(attach, &dmabuf->attachments, node) {
- if (!attach->peer2peer) {
+ if (!dma_buf_sgt_p2p_allowed(attach)) {
allow_vram = false;
break;
}
@@ -101,6 +92,8 @@ static void xe_dma_buf_unpin(struct dma_buf_attachment *attach)
static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach,
enum dma_data_direction dir)
{
+ struct device *dma_dev = dma_buf_sgt_dma_device(attach);
+ bool peer2peer = dma_buf_sgt_p2p_allowed(attach);
struct dma_buf *dma_buf = attach->dmabuf;
struct drm_gem_object *obj = dma_buf->priv;
struct xe_bo *bo = gem_to_xe_bo(obj);
@@ -108,11 +101,11 @@ static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach,
struct sg_table *sgt;
int r = 0;

- if (!attach->peer2peer && !xe_bo_can_migrate(bo, XE_PL_TT))
+ if (!peer2peer && !xe_bo_can_migrate(bo, XE_PL_TT))
return ERR_PTR(-EOPNOTSUPP);

if (!xe_bo_is_pinned(bo)) {
- if (!attach->peer2peer)
+ if (!peer2peer)
r = xe_bo_migrate(bo, XE_PL_TT, NULL, exec);
else
r = xe_bo_validate(bo, NULL, false, exec);
@@ -128,7 +121,7 @@ static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach,
if (IS_ERR(sgt))
return sgt;

- if (dma_map_sgtable(attach->dev, sgt, dir,
+ if (dma_map_sgtable(dma_dev, sgt, dir,
DMA_ATTR_SKIP_CPU_SYNC))
goto error_free;
break;
@@ -137,7 +130,7 @@ static struct sg_table *xe_dma_buf_map(struct dma_buf_attachment *attach,
case XE_PL_VRAM1:
r = xe_ttm_vram_mgr_alloc_sgt(xe_bo_device(bo),
bo->ttm.resource, 0,
- bo->ttm.base.size, attach->dev,
+ bo->ttm.base.size, dma_dev,
dir, &sgt);
if (r)
return ERR_PTR(r);
@@ -158,12 +151,14 @@ static void xe_dma_buf_unmap(struct dma_buf_attachment *attach,
struct sg_table *sgt,
enum dma_data_direction dir)
{
+ struct device *dma_dev = dma_buf_sgt_dma_device(attach);
+
if (sg_page(sgt->sgl)) {
- dma_unmap_sgtable(attach->dev, sgt, dir, 0);
+ dma_unmap_sgtable(dma_dev, sgt, dir, 0);
sg_free_table(sgt);
kfree(sgt);
} else {
- xe_ttm_vram_mgr_free_sgt(attach->dev, dir, sgt);
+ xe_ttm_vram_mgr_free_sgt(dma_dev, dir, sgt);
}
}

@@ -197,18 +192,39 @@ static int xe_dma_buf_begin_cpu_access(struct dma_buf *dma_buf,
return 0;
}

+static const struct dma_buf_mapping_sgt_exp_ops xe_dma_buf_sgt_ops = {
+ .map_dma_buf = xe_dma_buf_map,
+ .unmap_dma_buf = xe_dma_buf_unmap,
+};
+
+static int xe_dma_buf_match_mapping(struct dma_buf_match_args *args)
+{
+ struct drm_gem_object *obj = args->dmabuf->priv;
+ struct dma_buf_mapping_match sgt_match[2];
+ unsigned int num_match = 0;
+
+ if (IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY))
+ sgt_match[num_match++] = DMA_BUF_EMAPPING_SGT_P2P(
+ &xe_dma_buf_sgt_ops, to_pci_dev(obj->dev->dev));
+
+ if (xe_bo_can_migrate(gem_to_xe_bo(obj), XE_PL_TT))
+ sgt_match[num_match++] =
+ DMA_BUF_EMAPPING_SGT(&xe_dma_buf_sgt_ops);
+
+ return dma_buf_match_mapping(args, sgt_match, ARRAY_SIZE(sgt_match));
+}
+
static const struct dma_buf_ops xe_dmabuf_ops = {
.attach = xe_dma_buf_attach,
.detach = xe_dma_buf_detach,
.pin = xe_dma_buf_pin,
.unpin = xe_dma_buf_unpin,
- .map_dma_buf = xe_dma_buf_map,
- .unmap_dma_buf = xe_dma_buf_unmap,
.release = drm_gem_dmabuf_release,
.begin_cpu_access = xe_dma_buf_begin_cpu_access,
.mmap = drm_gem_dmabuf_mmap,
.vmap = drm_gem_dmabuf_vmap,
.vunmap = drm_gem_dmabuf_vunmap,
+ .match_mapping = xe_dma_buf_match_mapping,
};

struct dma_buf *xe_gem_prime_export(struct drm_gem_object *obj, int flags)
--
2.43.0