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)
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 | 59 +++++++++++++++++++++++++
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 18 +++-----
2 files changed, 66 insertions(+), 11 deletions(-)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index d3c369742124..465f9d4a79d7 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.
*/
@@ -468,6 +500,33 @@ int amdgpu_gem_create_ioctl(struct drm_device *dev, void
*data,
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 |
AMDGPU_GEM_DOMAIN_GWS | AMDGPU_GEM_DOMAIN_OA)) {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index 0e301cab74e0..14af9b0b8673 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1854,14 +1854,13 @@ static void amdgpu_ttm_pools_fini(struct amdgpu_device
*adev)
}
/**
- * amdgpu_ttm_mmio_remap_bo_init - allocate the singleton 4K MMIO_REMAP BO
+ * amdgpu_ttm_mmio_remap_bo_init - Allocate the singleton 4K MMIO_REMAP BO
* @adev: amdgpu device
*
* Allocates a one-page (4K) GEM BO in AMDGPU_GEM_DOMAIN_MMIO_REMAP when the
* hardware exposes a remap base (adev->rmmio_remap.bus_addr) and the host
* PAGE_SIZE is <= AMDGPU_GPU_PAGE_SIZE (4K). The BO is created as a regular
- * GEM object (amdgpu_bo_create), then reserved and kmap’ed once to exercise
- * the io-mem setup path. If prerequisites are not met, this is a no-op.
+ * GEM object (amdgpu_bo_create).
*
* Return:
* * 0 on success or intentional skip (feature not present/unsupported)
@@ -1871,16 +1870,13 @@ static int amdgpu_ttm_mmio_remap_bo_init(struct
amdgpu_device *adev)
{
int r;
struct amdgpu_bo_param bp = { 0 };
- void *kptr;
- /* Skip if HW doesn’t expose remap or system PAGE > GPU 4K */
+ /* Skip if HW doesn’t expose remap or
+ * Hardware remap page is fixed 4K; skip on larger PAGE_SIZE.
+ */
if (!adev->rmmio_remap.bus_addr || PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE)
return 0;
- /* Hardware remap page is fixed 4K; skip on larger PAGE_SIZE. */
- if (PAGE_SIZE > AMDGPU_GPU_PAGE_SIZE)
- return 0;
-
/* Create exactly one GEM BO in the MMIO_REMAP domain. */
bp.type = ttm_bo_type_device; /* userspace-mappable GEM
*/
bp.size = AMDGPU_GPU_PAGE_SIZE; /* 4K */
@@ -1898,7 +1894,7 @@ static int amdgpu_ttm_mmio_remap_bo_init(struct
amdgpu_device *adev)
}
/**
- * amdgpu_ttm_mmio_remap_bo_fini - free the singleton MMIO_REMAP BO
+ * amdgpu_ttm_mmio_remap_bo_fini - Free the singleton MMIO_REMAP BO
* @adev: amdgpu device
*
* Frees the kernel-owned MMIO_REMAP BO if it was allocated by
@@ -1907,7 +1903,7 @@ static int amdgpu_ttm_mmio_remap_bo_init(struct
amdgpu_device *adev)
static void amdgpu_ttm_mmio_remap_bo_fini(struct amdgpu_device *adev)
{
amdgpu_bo_unref(&adev->rmmio_remap.bo);
- adev->mmio_remap.bo = NULL;
+ adev->rmmio_remap.bo = NULL;
}
/*
--
2.34.1
