powerpc/powernv: Use the security flags in pnv_setup_rfi_flush()

CVE-2018-3639 (powerpc)

Now that we have the security flags we can significantly simplify the
code in pnv_setup_rfi_flush(), because we can use the flags instead of
checking device tree properties and because the security flags have
pessimistic defaults.

(cherry picked from commit 37c0bdd0)
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>

arch/powerpc/platforms/powernv/setup.c

@@ -65,7 +65,7 @@ static void init_fw_feat_flags(struct device_node *np)
 	if (fw_feature_is("enabled", "fw-bcctrl-serialized", np))
 		security_ftr_set(SEC_FTR_BCCTRL_SERIALISED);
 
-	if (fw_feature_is("enabled", "inst-spec-barrier-ori31,31,0", np))
+	if (fw_feature_is("enabled", "inst-l1d-flush-ori30,30,0", np))
 		security_ftr_set(SEC_FTR_L1D_FLUSH_ORI30);
 
 	if (fw_feature_is("enabled", "inst-l1d-flush-trig2", np))
@@ -98,11 +98,10 @@ static void pnv_setup_rfi_flush(void)
 {
 	struct device_node *np, *fw_features;
 	enum l1d_flush_type type;
-	int enable;
+	bool enable;
 
 	/* Default to fallback in case fw-features are not available */
 	type = L1D_FLUSH_FALLBACK;
-	enable = 1;
 
 	np = of_find_node_by_name(NULL, "ibm,opal");
 	fw_features = of_get_child_by_name(np, "fw-features");
@@ -110,40 +109,20 @@ static void pnv_setup_rfi_flush(void)
 
 	if (fw_features) {
 		init_fw_feat_flags(fw_features);
+		of_node_put(fw_features);
 
-		np = of_get_child_by_name(fw_features, "inst-l1d-flush-trig2");
-		if (np && of_property_read_bool(np, "enabled"))
+		if (security_ftr_enabled(SEC_FTR_L1D_FLUSH_TRIG2))
 			type = L1D_FLUSH_MTTRIG;
 
-		of_node_put(np);
-
-		np = of_get_child_by_name(fw_features, "inst-l1d-flush-ori30,30,0");
-		if (np && of_property_read_bool(np, "enabled"))
+		if (security_ftr_enabled(SEC_FTR_L1D_FLUSH_ORI30))
 			type = L1D_FLUSH_ORI;
-
-		of_node_put(np);
-
-		/* Enable unless firmware says NOT to */
-		enable = 2;
-		np = of_get_child_by_name(fw_features, "needs-l1d-flush-msr-hv-1-to-0");
-		if (np && of_property_read_bool(np, "disabled"))
-			enable--;
-
-		of_node_put(np);
-
-		np = of_get_child_by_name(fw_features, "needs-l1d-flush-msr-pr-0-to-1");
-		if (np && of_property_read_bool(np, "disabled"))
-			enable--;
-
-		np = of_get_child_by_name(fw_features, "speculation-policy-favor-security");
-		if (np && of_property_read_bool(np, "disabled"))
-			enable = 0;
-
-		of_node_put(np);
-		of_node_put(fw_features);
 	}
 
-	setup_rfi_flush(type, enable > 0);
+	enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) && \
+		 (security_ftr_enabled(SEC_FTR_L1D_FLUSH_PR)   || \
+		  security_ftr_enabled(SEC_FTR_L1D_FLUSH_HV));
+
+	setup_rfi_flush(type, enable);
 }
 
 static void __init pnv_setup_arch(void)