drm/amd/amdgpu:save psp ring wptr to avoid attack

[Why]
When some tools performing psp mailbox attack, the readback value
of register can be a random value which may break psp.

[How]
Use a psp wptr cache machanism to aovid the change made by attack.

v2: unify change and add detailed reason

Signed-off-by: Victor Zhao <Victor.Zhao@amd.com>
Signed-off-by: Jingwen Chen <Jingwen.Chen2@amd.com>
Reviewed-by: Monk Liu <monk.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_psp.h

@@ -76,6 +76,7 @@ struct psp_ring
 	uint64_t			ring_mem_mc_addr;
 	void				*ring_mem_handle;
 	uint32_t			ring_size;
+	uint32_t			ring_wptr;
 };
 
 /* More registers may will be supported */

drivers/gpu/drm/amd/amdgpu/psp_v11_0.c

@@ -720,7 +720,7 @@ static uint32_t psp_v11_0_ring_get_wptr(struct psp_context *psp)
 	struct amdgpu_device *adev = psp->adev;
 
 	if (amdgpu_sriov_vf(adev))
-		data = RREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_102);
+		data = psp->km_ring.ring_wptr;
 	else
 		data = RREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_67);
 
@@ -734,6 +734,7 @@ static void psp_v11_0_ring_set_wptr(struct psp_context *psp, uint32_t value)
 	if (amdgpu_sriov_vf(adev)) {
 		WREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_102, value);
 		WREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_101, GFX_CTRL_CMD_ID_CONSUME_CMD);
+		psp->km_ring.ring_wptr = value;
 	} else
 		WREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_67, value);
 }

drivers/gpu/drm/amd/amdgpu/psp_v3_1.c

@@ -379,7 +379,7 @@ static uint32_t psp_v3_1_ring_get_wptr(struct psp_context *psp)
 	struct amdgpu_device *adev = psp->adev;
 
 	if (amdgpu_sriov_vf(adev))
-		data = RREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_102);
+		data = psp->km_ring.ring_wptr;
 	else
 		data = RREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_67);
 	return data;
@@ -394,6 +394,7 @@ static void psp_v3_1_ring_set_wptr(struct psp_context *psp, uint32_t value)
 		/* send interrupt to PSP for SRIOV ring write pointer update */
 		WREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_101,
 			GFX_CTRL_CMD_ID_CONSUME_CMD);
+		psp->km_ring.ring_wptr = value;
 	} else
 		WREG32_SOC15(MP0, 0, mmMP0_SMN_C2PMSG_67, value);
 }