linux-kernel - [PATCH 2/2] drm/msm: Add modparam to allow vram carveout

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Date:   Wed, 30 Dec 2020 17:29:43 +0200
From:   Iskren Chernev <iskren.chernev@...il.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Akhil P Oommen <akhilpo@...eaurora.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Brian Masney <masneyb@...tation.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        Iskren Chernev <iskren.chernev@...il.com>,
        Jonathan Marek <jonathan@...ek.ca>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sean Paul <sean@...rly.run>,
        Sharat Masetty <smasetty@...eaurora.org>,
        Shawn Guo <shawn.guo@...aro.org>,
        Wambui Karuga <wambui.karugax@...il.com>,
        ~postmarketos/upstreaming@...ts.sr.ht
Subject: [PATCH 2/2] drm/msm: Add modparam to allow vram carveout

Using the GPU with a VRAM Carveout is a security vulnerability.
Nevertheless it is sometimes required, especially when no IOMMU
implementation is available for a certain platform.

Signed-off-by: Iskren Chernev <iskren.chernev@...il.com>
---
 drivers/gpu/drm/msm/adreno/a2xx_gpu.c      | 6 ++++--
 drivers/gpu/drm/msm/adreno/a3xx_gpu.c      | 6 ++++--
 drivers/gpu/drm/msm/adreno/a4xx_gpu.c      | 6 ++++--
 drivers/gpu/drm/msm/adreno/adreno_device.c | 4 ++++
 drivers/gpu/drm/msm/adreno/adreno_gpu.h    | 1 +
 5 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/msm/adreno/a2xx_gpu.c b/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
index 7e82c41a85f1a..bdc989183c648 100644
--- a/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a2xx_gpu.c
@@ -534,8 +534,10 @@ struct msm_gpu *a2xx_gpu_init(struct drm_device *dev)
 
 	if (!gpu->aspace) {
 		dev_err(dev->dev, "No memory protection without MMU\n");
-		ret = -ENXIO;
-		goto fail;
+		if (!allow_vram_carveout) {
+			ret = -ENXIO;
+			goto fail;
+		}
 	}
 
 	return gpu;
diff --git a/drivers/gpu/drm/msm/adreno/a3xx_gpu.c b/drivers/gpu/drm/msm/adreno/a3xx_gpu.c
index 93da6683a8661..4534633fe7cdb 100644
--- a/drivers/gpu/drm/msm/adreno/a3xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a3xx_gpu.c
@@ -564,8 +564,10 @@ struct msm_gpu *a3xx_gpu_init(struct drm_device *dev)
 		 * implement a cmdstream validator.
 		 */
 		DRM_DEV_ERROR(dev->dev, "No memory protection without IOMMU\n");
-		ret = -ENXIO;
-		goto fail;
+		if (!allow_vram_carveout) {
+			ret = -ENXIO;
+			goto fail;
+		}
 	}
 
 	icc_path = devm_of_icc_get(&pdev->dev, "gfx-mem");
diff --git a/drivers/gpu/drm/msm/adreno/a4xx_gpu.c b/drivers/gpu/drm/msm/adreno/a4xx_gpu.c
index c0be3a0f36b2c..82bebb40234de 100644
--- a/drivers/gpu/drm/msm/adreno/a4xx_gpu.c
+++ b/drivers/gpu/drm/msm/adreno/a4xx_gpu.c
@@ -692,8 +692,10 @@ struct msm_gpu *a4xx_gpu_init(struct drm_device *dev)
 		 * implement a cmdstream validator.
 		 */
 		DRM_DEV_ERROR(dev->dev, "No memory protection without IOMMU\n");
-		ret = -ENXIO;
-		goto fail;
+		if (!allow_vram_carveout) {
+			ret = -ENXIO;
+			goto fail;
+		}
 	}
 
 	icc_path = devm_of_icc_get(&pdev->dev, "gfx-mem");
diff --git a/drivers/gpu/drm/msm/adreno/adreno_device.c b/drivers/gpu/drm/msm/adreno/adreno_device.c
index 87c8b033ad1a6..12e75ba360f95 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_device.c
+++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
@@ -18,6 +18,10 @@ bool snapshot_debugbus = false;
 MODULE_PARM_DESC(snapshot_debugbus, "Include debugbus sections in GPU devcoredump (if not fused off)");
 module_param_named(snapshot_debugbus, snapshot_debugbus, bool, 0600);
 
+bool allow_vram_carveout = false;
+MODULE_PARM_DESC(allow_vram_carveout, "Allow using VRAM Carveout, in place of IOMMU");
+module_param_named(allow_vram_carveout, allow_vram_carveout, bool, 0600);
+
 static const struct adreno_info gpulist[] = {
 	{
 		.rev   = ADRENO_REV(2, 0, 0, 0),
diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.h b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
index c3775f79525a7..fe5444a1482ae 100644
--- a/drivers/gpu/drm/msm/adreno/adreno_gpu.h
+++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
@@ -18,6 +18,7 @@
 #include "adreno_pm4.xml.h"
 
 extern bool snapshot_debugbus;
+extern bool allow_vram_carveout;
 
 enum {
 	ADRENO_FW_PM4 = 0,
-- 
2.29.2