[PATCH 1/2] drm/amdgpu: Detect if amdgpu in IOMMU isolation mode

[Philip Yang]

If host and amdgpu IOMMU is not enabled or IOMMU is pass through mode,
dma_map_page return address is equal to page physical address, use this
to set adev->iommu_isolation flag which will be used to optimize memory
usage for multi GPU mappings.

Signed-off-by: Philip Yang <Philip.Yang at amd.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  2 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 27 ++++++++++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index c5cfe2926ca1..fbbe8c7b5d0c 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1097,6 +1097,8 @@ struct amdgpu_device {
 
 	struct amdgpu_reset_control     *reset_cntl;
 	uint32_t                        ip_versions[MAX_HWIP][HWIP_MAX_INSTANCE];
+
+	bool				iommu_isolation;
 };
 
 static inline struct amdgpu_device *drm_to_adev(struct drm_device *ddev)
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 3c5afa45173c..6d0f3c477670 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -3364,6 +3364,31 @@ static int amdgpu_device_get_job_timeout_settings(struct amdgpu_device *adev)
 	return ret;
 }
 
+/**
+ * amdgpu_device_check_iommu_isolation - check if IOMMU isolation is enabled
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * device is in IOMMU isolation mode if dma_map_page return address is not equal
+ * to page physical address.
+ */
+static void amdgpu_device_check_iommu_isolation(struct amdgpu_device *adev)
+{
+	struct page *page;
+	dma_addr_t addr;
+
+	page = alloc_page(GFP_KERNEL);
+	if (!page)
+		return;
+	addr = dma_map_page(adev->dev, page, 0, PAGE_SIZE, DMA_BIDIRECTIONAL);
+	if (dma_mapping_error(adev->dev, addr))
+		goto out_free_page;
+	adev->iommu_isolation = (addr != page_to_phys(page));
+	dma_unmap_page(adev->dev, addr, PAGE_SIZE, DMA_BIDIRECTIONAL);
+out_free_page:
+	__free_page(page);
+}
+
 static const struct attribute *amdgpu_dev_attributes[] = {
 	&dev_attr_product_name.attr,
 	&dev_attr_product_number.attr,
@@ -3767,6 +3792,8 @@ int amdgpu_device_init(struct amdgpu_device *adev,
 		queue_delayed_work(system_wq, &mgpu_info.delayed_reset_work,
 				   msecs_to_jiffies(AMDGPU_RESUME_MS));
 
+	amdgpu_device_check_iommu_isolation(adev);
+
 	return 0;
 
 release_ras_con:
-- 
2.17.1