[Linaro-mm-sig] Re: [PATCH v3 2/7] dma-buf: Always build with DMABUF_MOVE_NOTIFY

On 1/20/26 15:07, Leon Romanovsky wrote:

From: Leon Romanovsky leonro@nvidia.com

DMABUF_MOVE_NOTIFY was introduced in 2018 and has been marked as experimental and disabled by default ever since. Six years later, all new importers implement this callback.

It is therefore reasonable to drop CONFIG_DMABUF_MOVE_NOTIFY and always build DMABUF with support for it enabled.

Suggested-by: Christian König christian.koenig@amd.com Signed-off-by: Leon Romanovsky leonro@nvidia.com

---

drivers/dma-buf/Kconfig | 12 ------------ drivers/dma-buf/dma-buf.c | 12 ++---------- drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 10 +++------- drivers/gpu/drm/amd/amdkfd/Kconfig | 2 +- drivers/gpu/drm/xe/tests/xe_dma_buf.c | 3 +-- drivers/gpu/drm/xe/xe_dma_buf.c | 12 ++++-------- 6 files changed, 11 insertions(+), 40 deletions(-)

diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig index b46eb8a552d7..84d5e9b24e20 100644 --- a/drivers/dma-buf/Kconfig +++ b/drivers/dma-buf/Kconfig @@ -40,18 +40,6 @@ config UDMABUF A driver to let userspace turn memfd regions into dma-bufs. Qemu can use this to create host dmabufs for guest framebuffers. -config DMABUF_MOVE_NOTIFY

• bool "Move notify between drivers (EXPERIMENTAL)"
• default n
• depends on DMA_SHARED_BUFFER
• help

•  Don't pin buffers if the dynamic DMA-buf interface is available on
  

•  both the exporter as well as the importer. This fixes a security
  

•  problem where userspace is able to pin unrestricted amounts of memory
  

•  through DMA-buf.
  

•  This is marked experimental because we don't yet have a consistent
  

•  execution context and memory management between drivers.
  

config DMABUF_DEBUG bool "DMA-BUF debug checks" depends on DMA_SHARED_BUFFER diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 59cc647bf40e..cd3b60ce4863 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -837,18 +837,10 @@ static void mangle_sg_table(struct sg_table *sg_table) } -static inline bool -dma_buf_attachment_is_dynamic(struct dma_buf_attachment *attach)

I would rather like to keep the wrapper and even add some explanation what it means when true is returned.

Apart from that looks good to me.

Regards, Christian.

-{

• return !!attach->importer_ops;

-}

static bool dma_buf_pin_on_map(struct dma_buf_attachment *attach) {

• return attach->dmabuf->ops->pin &&

• (!dma_buf_attachment_is_dynamic(attach) ||
  

•  !IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY));
  

• return attach->dmabuf->ops->pin && !attach->importer_ops;

} /** @@ -1124,7 +1116,7 @@ struct sg_table *dma_buf_map_attachment(struct dma_buf_attachment *attach, /* * Importers with static attachments don't wait for fences. */

• if (!dma_buf_attachment_is_dynamic(attach)) {

• if (!attach->importer_ops) { ret = dma_resv_wait_timeout(attach->dmabuf->resv, DMA_RESV_USAGE_KERNEL, true, MAX_SCHEDULE_TIMEOUT);

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c index 863454148b28..349215549e8f 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c @@ -145,13 +145,9 @@ static int amdgpu_dma_buf_pin(struct dma_buf_attachment *attach) * notifiers are disabled, only allow pinning in VRAM when move * notiers are enabled. */

• if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {

• domains &= ~AMDGPU_GEM_DOMAIN_VRAM;
  

• } else {

• list_for_each_entry(attach, &dmabuf->attachments, node)
  

• 	if (!attach->peer2peer)
  

• 		domains &= ~AMDGPU_GEM_DOMAIN_VRAM;
  

• }

• list_for_each_entry(attach, &dmabuf->attachments, node)

• if (!attach->peer2peer)
  

• 	domains &= ~AMDGPU_GEM_DOMAIN_VRAM;
  

if (domains & AMDGPU_GEM_DOMAIN_VRAM) bo->flags |= AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED; diff --git a/drivers/gpu/drm/amd/amdkfd/Kconfig b/drivers/gpu/drm/amd/amdkfd/Kconfig index 16e12c9913f9..a5d7467c2f34 100644 --- a/drivers/gpu/drm/amd/amdkfd/Kconfig +++ b/drivers/gpu/drm/amd/amdkfd/Kconfig @@ -27,7 +27,7 @@ config HSA_AMD_SVM config HSA_AMD_P2P bool "HSA kernel driver support for peer-to-peer for AMD GPU devices"

• depends on HSA_AMD && PCI_P2PDMA && DMABUF_MOVE_NOTIFY

• depends on HSA_AMD && PCI_P2PDMA help Enable peer-to-peer (P2P) communication between AMD GPUs over the PCIe bus. This can improve performance of multi-GPU compute

diff --git a/drivers/gpu/drm/xe/tests/xe_dma_buf.c b/drivers/gpu/drm/xe/tests/xe_dma_buf.c index 1f2cca5c2f81..c107687ef3c0 100644 --- a/drivers/gpu/drm/xe/tests/xe_dma_buf.c +++ b/drivers/gpu/drm/xe/tests/xe_dma_buf.c @@ -22,8 +22,7 @@ static bool p2p_enabled(struct dma_buf_test_params *params) static bool is_dynamic(struct dma_buf_test_params *params) {

• return IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY) && params->attach_ops &&

• params->attach_ops->invalidate_mappings;
  

• return params->attach_ops && params->attach_ops->invalidate_mappings;

} static void check_residency(struct kunit *test, struct xe_bo *exported, diff --git a/drivers/gpu/drm/xe/xe_dma_buf.c b/drivers/gpu/drm/xe/xe_dma_buf.c index 1b9cd043e517..ea370cd373e9 100644 --- a/drivers/gpu/drm/xe/xe_dma_buf.c +++ b/drivers/gpu/drm/xe/xe_dma_buf.c @@ -56,14 +56,10 @@ static int xe_dma_buf_pin(struct dma_buf_attachment *attach) bool allow_vram = true; int ret;

• if (!IS_ENABLED(CONFIG_DMABUF_MOVE_NOTIFY)) {

• allow_vram = false;
  

• } else {

• list_for_each_entry(attach, &dmabuf->attachments, node) {
  

• 	if (!attach->peer2peer) {
  

• 		allow_vram = false;
  

• 		break;
  

• 	}
  

• list_for_each_entry(attach, &dmabuf->attachments, node) {

• if (!attach->peer2peer) {
  

• 	allow_vram = false;
  

• 	break;
  

  } }