[PATCH v4 4/4] drm/amdgpu: do not pass AMDGPU_FENCE_FLAG_64BIT to media rings

[jbmoore <jbmoore61@gmail.com>]

From: "John B. Moore" <jbmoore61@gmail.com>

amdgpu_ib_schedule() unconditionally ORs AMDGPU_FENCE_FLAG_64BIT into
the flags when emitting the user fence for every ring type:

  amdgpu_ring_emit_fence(ring, job->uf_addr, job->uf_sequence,
                         fence_flags | AMDGPU_FENCE_FLAG_64BIT);

VCN, UVD, VCE, and JPEG encoder/decoder rings only support 32-bit
fence values.  Their emit_fence callbacks contain bare WARN_ON()
assertions for this flag, but the flag should never reach them in
the first place.

The VCN_ENC_CMD_FENCE hardware packet writes a single 32-bit
sequence value to a 64-bit GPU address.  There is no 64-bit fence
variant in the VCN/UVD/VCE/JPEG command sets.

Filter AMDGPU_FENCE_FLAG_64BIT at the call site in
amdgpu_ib_schedule(), only setting it for ring types whose hardware
supports 64-bit fence writes: GFX, compute, SDMA, KIQ, MES, and VPE.

Also convert the bare WARN_ON() guards in the five affected VCN
callbacks to WARN_ON_ONCE() to prevent kernel log flooding if
the condition is somehow triggered via another path.

Found by a custom amdgpu DRM ioctl fuzzer.

Fixes: c660f40b1ef3 ("drm/amdgpu: fix user fence write race condition")
Signed-off-by: John B. Moore <jbmoore61@gmail.com>
Cc: stable@vger.kernel.org
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c   | 18 +++++++++++++++++-
 drivers/gpu/drm/amd/amdgpu/vcn_sw_ring.c |  2 +-
 drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c    |  4 ++--
 drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c    |  4 ++--
 4 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
index f1ed4a436..3c32a6197 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
@@ -297,8 +297,24 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned int num_ibs,
 
 	/* wrap the last IB with fence */
 	if (job && job->uf_addr) {
+		unsigned int uf_flags = fence_flags;
+
+		/*
+		 * Only request 64-bit fence writes on rings whose hardware
+		 * supports them.  VCN/UVD/VCE/JPEG rings only support 32-bit
+		 * fence values; passing AMDGPU_FENCE_FLAG_64BIT causes their
+		 * emit_fence callbacks to WARN and emit a truncated fence.
+		 */
+		if (ring->funcs->type == AMDGPU_RING_TYPE_GFX ||
+		    ring->funcs->type == AMDGPU_RING_TYPE_COMPUTE ||
+		    ring->funcs->type == AMDGPU_RING_TYPE_SDMA ||
+		    ring->funcs->type == AMDGPU_RING_TYPE_KIQ ||
+		    ring->funcs->type == AMDGPU_RING_TYPE_MES ||
+		    ring->funcs->type == AMDGPU_RING_TYPE_VPE)
+			uf_flags |= AMDGPU_FENCE_FLAG_64BIT;
+
 		amdgpu_ring_emit_fence(ring, job->uf_addr, job->uf_sequence,
-				       fence_flags | AMDGPU_FENCE_FLAG_64BIT);
+				       uf_flags);
 	}
 
 	if (ring->funcs->emit_gfx_shadow && ring->funcs->init_cond_exec &&
diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_sw_ring.c b/drivers/gpu/drm/amd/amdgpu/vcn_sw_ring.c
index 2b9ddb3d2..9adc7607c 100644
--- a/drivers/gpu/drm/amd/amdgpu/vcn_sw_ring.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_sw_ring.c
@@ -27,7 +27,7 @@
 void vcn_dec_sw_ring_emit_fence(struct amdgpu_ring *ring, u64 addr,
 	u64 seq, uint32_t flags)
 {
-	WARN_ON(flags & AMDGPU_FENCE_FLAG_64BIT);
+	WARN_ON_ONCE(flags & AMDGPU_FENCE_FLAG_64BIT);
 
 	amdgpu_ring_write(ring, VCN_DEC_SW_CMD_FENCE);
 	amdgpu_ring_write(ring, addr);
diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
index e9d790914..729c1c378 100644
--- a/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_v1_0.c
@@ -1548,7 +1548,7 @@ static void vcn_v1_0_dec_ring_emit_fence(struct amdgpu_ring *ring, u64 addr, u64
 {
 	struct amdgpu_device *adev = ring->adev;
 
-	WARN_ON(flags & AMDGPU_FENCE_FLAG_64BIT);
+	WARN_ON_ONCE(flags & AMDGPU_FENCE_FLAG_64BIT);
 
 	amdgpu_ring_write(ring,
 		PACKET0(SOC15_REG_OFFSET(UVD, 0, mmUVD_CONTEXT_ID), 0));
@@ -1724,7 +1724,7 @@ static void vcn_v1_0_enc_ring_set_wptr(struct amdgpu_ring *ring)
 static void vcn_v1_0_enc_ring_emit_fence(struct amdgpu_ring *ring, u64 addr,
 			u64 seq, unsigned flags)
 {
-	WARN_ON(flags & AMDGPU_FENCE_FLAG_64BIT);
+	WARN_ON_ONCE(flags & AMDGPU_FENCE_FLAG_64BIT);
 
 	amdgpu_ring_write(ring, VCN_ENC_CMD_FENCE);
 	amdgpu_ring_write(ring, addr);
diff --git a/drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c b/drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c
index e35fae9cd..a020140fb 100644
--- a/drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c
+++ b/drivers/gpu/drm/amd/amdgpu/vcn_v2_0.c
@@ -1537,7 +1537,7 @@ void vcn_v2_0_dec_ring_emit_fence(struct amdgpu_ring *ring, u64 addr, u64 seq,
 {
 	struct amdgpu_device *adev = ring->adev;
 
-	WARN_ON(flags & AMDGPU_FENCE_FLAG_64BIT);
+	WARN_ON_ONCE(flags & AMDGPU_FENCE_FLAG_64BIT);
 	amdgpu_ring_write(ring, PACKET0(adev->vcn.inst[ring->me].internal.context_id, 0));
 	amdgpu_ring_write(ring, seq);
 
@@ -1722,7 +1722,7 @@ static void vcn_v2_0_enc_ring_set_wptr(struct amdgpu_ring *ring)
 void vcn_v2_0_enc_ring_emit_fence(struct amdgpu_ring *ring, u64 addr,
 				u64 seq, unsigned flags)
 {
-	WARN_ON(flags & AMDGPU_FENCE_FLAG_64BIT);
+	WARN_ON_ONCE(flags & AMDGPU_FENCE_FLAG_64BIT);
 
 	amdgpu_ring_write(ring, VCN_ENC_CMD_FENCE);
 	amdgpu_ring_write(ring, addr);
-- 
2.43.0