EDAC/amd64: Check return value of amd_smn_read()

Check the return value of amd_smn_read() before saving a value. This
ensures invalid values aren't saved. The struct umc instance is
initialized to 0 during memory allocation. Therefore, a bad read will
keep the value as 0 providing the expected Read-as-Zero behavior.

Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://lore.kernel.org/r/20240606-fix-smn-bad-read-v4-2-ffde21931c3f@amd.com

Author: yghannam

drivers/edac/amd64_edac.c

@@ -1438,6 +1438,7 @@ static void umc_read_base_mask(struct amd64_pvt *pvt)
 	u32 *base, *base_sec;
 	u32 *mask, *mask_sec;
 	int cs, umc;
+	u32 tmp;
 
 	for_each_umc(umc) {
 		umc_base_reg = get_umc_base(umc) + UMCCH_BASE_ADDR;
@@ -1450,13 +1451,17 @@ static void umc_read_base_mask(struct amd64_pvt *pvt)
 			base_reg = umc_base_reg + (cs * 4);
 			base_reg_sec = umc_base_reg_sec + (cs * 4);
 
-			if (!amd_smn_read(pvt->mc_node_id, base_reg, base))
+			if (!amd_smn_read(pvt->mc_node_id, base_reg, &tmp)) {
+				*base = tmp;
 				edac_dbg(0, "  DCSB%d[%d]=0x%08x reg: 0x%x\n",
 					 umc, cs, *base, base_reg);
+			}
 
-			if (!amd_smn_read(pvt->mc_node_id, base_reg_sec, base_sec))
+			if (!amd_smn_read(pvt->mc_node_id, base_reg_sec, &tmp)) {
+				*base_sec = tmp;
 				edac_dbg(0, "    DCSB_SEC%d[%d]=0x%08x reg: 0x%x\n",
 					 umc, cs, *base_sec, base_reg_sec);
+			}
 		}
 
 		umc_mask_reg = get_umc_base(umc) + UMCCH_ADDR_MASK;
@@ -1469,13 +1474,17 @@ static void umc_read_base_mask(struct amd64_pvt *pvt)
 			mask_reg = umc_mask_reg + (cs * 4);
 			mask_reg_sec = umc_mask_reg_sec + (cs * 4);
 
-			if (!amd_smn_read(pvt->mc_node_id, mask_reg, mask))
+			if (!amd_smn_read(pvt->mc_node_id, mask_reg, &tmp)) {
+				*mask = tmp;
 				edac_dbg(0, "  DCSM%d[%d]=0x%08x reg: 0x%x\n",
 					 umc, cs, *mask, mask_reg);
+			}
 
-			if (!amd_smn_read(pvt->mc_node_id, mask_reg_sec, mask_sec))
+			if (!amd_smn_read(pvt->mc_node_id, mask_reg_sec, &tmp)) {
+				*mask_sec = tmp;
 				edac_dbg(0, "    DCSM_SEC%d[%d]=0x%08x reg: 0x%x\n",
 					 umc, cs, *mask_sec, mask_reg_sec);
+			}
 		}
 	}
 }
@@ -2894,19 +2903,28 @@ static void umc_read_mc_regs(struct amd64_pvt *pvt)
 {
 	u8 nid = pvt->mc_node_id;
 	struct amd64_umc *umc;
-	u32 i, umc_base;
+	u32 i, tmp, umc_base;
 
 	/* Read registers from each UMC */
 	for_each_umc(i) {
 
 		umc_base = get_umc_base(i);
 		umc = &pvt->umc[i];
 
-		amd_smn_read(nid, umc_base + get_umc_reg(pvt, UMCCH_DIMM_CFG), &umc->dimm_cfg);
-		amd_smn_read(nid, umc_base + UMCCH_UMC_CFG, &umc->umc_cfg);
-		amd_smn_read(nid, umc_base + UMCCH_SDP_CTRL, &umc->sdp_ctrl);
-		amd_smn_read(nid, umc_base + UMCCH_ECC_CTRL, &umc->ecc_ctrl);
-		amd_smn_read(nid, umc_base + UMCCH_UMC_CAP_HI, &umc->umc_cap_hi);
+		if (!amd_smn_read(nid, umc_base + get_umc_reg(pvt, UMCCH_DIMM_CFG), &tmp))
+			umc->dimm_cfg = tmp;
+
+		if (!amd_smn_read(nid, umc_base + UMCCH_UMC_CFG, &tmp))
+			umc->umc_cfg = tmp;
+
+		if (!amd_smn_read(nid, umc_base + UMCCH_SDP_CTRL, &tmp))
+			umc->sdp_ctrl = tmp;
+
+		if (!amd_smn_read(nid, umc_base + UMCCH_ECC_CTRL, &tmp))
+			umc->ecc_ctrl = tmp;
+
+		if (!amd_smn_read(nid, umc_base + UMCCH_UMC_CAP_HI, &tmp))
+			umc->umc_cap_hi = tmp;
 	}
 }
 
@@ -3635,16 +3653,21 @@ static void gpu_read_mc_regs(struct amd64_pvt *pvt)
 {
 	u8 nid = pvt->mc_node_id;
 	struct amd64_umc *umc;
-	u32 i, umc_base;
+	u32 i, tmp, umc_base;
 
 	/* Read registers from each UMC */
 	for_each_umc(i) {
 		umc_base = gpu_get_umc_base(pvt, i, 0);
 		umc = &pvt->umc[i];
 
-		amd_smn_read(nid, umc_base + UMCCH_UMC_CFG, &umc->umc_cfg);
-		amd_smn_read(nid, umc_base + UMCCH_SDP_CTRL, &umc->sdp_ctrl);
-		amd_smn_read(nid, umc_base + UMCCH_ECC_CTRL, &umc->ecc_ctrl);
+		if (!amd_smn_read(nid, umc_base + UMCCH_UMC_CFG, &tmp))
+			umc->umc_cfg = tmp;
+
+		if (!amd_smn_read(nid, umc_base + UMCCH_SDP_CTRL, &tmp))
+			umc->sdp_ctrl = tmp;
+
+		if (!amd_smn_read(nid, umc_base + UMCCH_ECC_CTRL, &tmp))
+			umc->ecc_ctrl = tmp;
 	}
 }