Enable userspace to obtain a handle to the kernel-owned MMIO_REMAP
singleton when AMDGPU_GEM_DOMAIN_MMIO_REMAP is requested via
amdgpu_gem_create_ioctl().
Validate the fixed 4K constraint: if PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE
return -EINVAL; when provided, size and alignment must equal
AMDGPU_GPU_PAGE_SIZE.
If the singleton BO is not available, return -ENODEV.
v2:
- Drop READ_ONCE() on adev->mmio_remap.bo (use a plain pointer load).
The pointer is set `bo = adev->mmio_remap.bo;` ie., The pointer is
written once during init and not changed while IOCTLs run. There’s no
concurrent writer in this execution path, so a normal read is safe.
(Alex)
v3:
- Drop early -EINVAL for AMDGPU_GEM_DOMAIN_MMIO_REMAP; let the
MMIO_REMAP fast-path handle it and return the singleton handle.
Cc: Christian König <christian.koe...@amd.com>
Suggested-by: Alex Deucher <alexander.deuc...@amd.com>
Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmu...@amd.com>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 61 ++++++++++++++++++++++++-
1 file changed, 59 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index d3c369742124..7f331c34e581 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -424,6 +424,38 @@ const struct drm_gem_object_funcs amdgpu_gem_object_funcs
= {
.vm_ops = &amdgpu_gem_vm_ops,
};
+/**
+ * amdgpu_gem_get_mmio_remap_handle - Create a GEM handle for the MMIO_REMAP BO
+ * @file_priv: DRM file corresponding to the calling process
+ * @adev: amdgpu device
+ * @handle: returned userspace GEM handle (out)
+ *
+ * Creates a GEM handle to the kernel-owned singleton MMIO_REMAP buffer object
+ * (adev->rmmio_remap.bo). The BO is expected to be allocated during TTM init
+ * when the hardware exposes a remap base and PAGE_SIZE <= 4K.
+ *
+ * drm_gem_handle_create() acquires the handle reference, which will be dropped
+ * by GEM_CLOSE in userspace.
+ *
+ * * Return:
+ * * 0 on success
+ * * -ENODEV if the MMIO_REMAP BO is not available
+ * * A negative errno from drm_gem_handle_create() on failure
+ *
+ */
+static int amdgpu_gem_get_mmio_remap_handle(struct drm_file *file_priv,
+ struct amdgpu_device *adev,
+ u32 *handle)
+{
+ struct amdgpu_bo *bo = adev->rmmio_remap.bo;
+
+ if (!bo)
+ return -ENODEV;
+
+ /* drm_gem_handle_create() gets the ref; GEM_CLOSE drops it */
+ return drm_gem_handle_create(file_priv, &bo->tbo.base, handle);
+}
+
/*
* GEM ioctls.
*/
@@ -465,8 +497,33 @@ int amdgpu_gem_create_ioctl(struct drm_device *dev, void
*data,
/* always clear VRAM */
flags |= AMDGPU_GEM_CREATE_VRAM_CLEARED;
- if (args->in.domains & AMDGPU_GEM_DOMAIN_MMIO_REMAP)
- return -EINVAL;
+ /*
+ * === MMIO remap (HDP flush) fast-path ===
+ * If userspace asks for the MMIO_REMAP domain, don't allocate a new BO.
+ * Return a handle to the singleton BO created at ttm init.
+ */
+ if (args->in.domains & AMDGPU_GEM_DOMAIN_MMIO_REMAP) {
+ /*
+ * The MMIO remap page is fixed 4K on the GPU side. Do not
+ * allow use if the system PAGE_SIZE is larger than the GPU
+ * page size.
+ */
+ if (PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE)
+ return -EINVAL;
+
+ /* Enforce fixed size/alignment when provided by userspace. */
+ if (size && size != AMDGPU_GPU_PAGE_SIZE)
+ return -EINVAL;
+ if (args->in.alignment && args->in.alignment !=
AMDGPU_GPU_PAGE_SIZE)
+ return -EINVAL;
+
+ r = amdgpu_gem_get_mmio_remap_handle(filp, adev, &handle);
+ if (r)
+ return r;
+
+ args->out.handle = handle;
+ return 0;
+ }
/* create a gem object to contain this object in */
if (args->in.domains & (AMDGPU_GEM_DOMAIN_GDS |
--
2.34.1
