target/arm: Don't change pauth features when changing algorithm

We have cpu properties to adjust the pauth algorithm for the
purpose of speed of emulation.  Retain the set of pauth features
supported by the cpu even as the algorithm changes.

This already affects the neoverse-v1 cpu, which has FEAT_EPAC.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230829232335.965414-5-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/cpu64.c

@@ -473,37 +473,57 @@ void aarch64_add_sme_properties(Object *obj)
 
 void arm_cpu_pauth_finalize(ARMCPU *cpu, Error **errp)
 {
-    int arch_val = 0, impdef_val = 0;
-    uint64_t t;
+    ARMPauthFeature features = cpu_isar_feature(pauth_feature, cpu);
+    uint64_t isar1;
 
-    /* Exit early if PAuth is enabled, and fall through to disable it */
-    if ((kvm_enabled() || hvf_enabled()) && cpu->prop_pauth) {
-        if (!cpu_isar_feature(aa64_pauth, cpu)) {
-            error_setg(errp, "'pauth' feature not supported by %s on this host",
-                       kvm_enabled() ? "KVM" : "hvf");
-        }
+    /*
+     * These properties enable or disable Pauth as a whole, or change
+     * the pauth algorithm, but do not change the set of features that
+     * are present.  We have saved a copy of those features above and
+     * will now place it into the field that chooses the algorithm.
+     *
+     * Begin by disabling all fields.
+     */
+    isar1 = cpu->isar.id_aa64isar1;
+    isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, APA, 0);
+    isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, GPA, 0);
+    isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, API, 0);
+    isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, GPI, 0);
 
-        return;
-    }
+    if (kvm_enabled() || hvf_enabled()) {
+        /*
+         * Exit early if PAuth is enabled and fall through to disable it.
+         * The algorithm selection properties are not present.
+         */
+        if (cpu->prop_pauth) {
+            if (features == 0) {
+                error_setg(errp, "'pauth' feature not supported by "
+                           "%s on this host", current_accel_name());
+            }
+            return;
+        }
+    } else {
+        /* Pauth properties are only present when the model supports it. */
+        if (features == 0) {
+            assert(!cpu->prop_pauth);
+            return;
+        }
 
-    /* TODO: Handle HaveEnhancedPAC, HaveEnhancedPAC2, HaveFPAC. */
-    if (cpu->prop_pauth) {
-        if (cpu->prop_pauth_impdef) {
-            impdef_val = 1;
-        } else {
-            arch_val = 1;
+        if (cpu->prop_pauth) {
+            if (cpu->prop_pauth_impdef) {
+                isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, API, features);
+                isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, GPI, 1);
+            } else {
+                isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, APA, features);
+                isar1 = FIELD_DP64(isar1, ID_AA64ISAR1, GPA, 1);
+            }
+        } else if (cpu->prop_pauth_impdef) {
+            error_setg(errp, "cannot enable pauth-impdef without pauth");
+            error_append_hint(errp, "Add pauth=on to the CPU property list.\n");
         }
-    } else if (cpu->prop_pauth_impdef) {
-        error_setg(errp, "cannot enable pauth-impdef without pauth");
-        error_append_hint(errp, "Add pauth=on to the CPU property list.\n");
     }
 
-    t = cpu->isar.id_aa64isar1;
-    t = FIELD_DP64(t, ID_AA64ISAR1, APA, arch_val);
-    t = FIELD_DP64(t, ID_AA64ISAR1, GPA, arch_val);
-    t = FIELD_DP64(t, ID_AA64ISAR1, API, impdef_val);
-    t = FIELD_DP64(t, ID_AA64ISAR1, GPI, impdef_val);
-    cpu->isar.id_aa64isar1 = t;
+    cpu->isar.id_aa64isar1 = isar1;
 }
 
 static Property arm_cpu_pauth_property =

target/arm/tcg/cpu64.c

@@ -803,6 +803,8 @@ void aarch64_max_tcg_initfn(Object *obj)
 
     t = cpu->isar.id_aa64isar1;
     t = FIELD_DP64(t, ID_AA64ISAR1, DPB, 2);      /* FEAT_DPB2 */
+    t = FIELD_DP64(t, ID_AA64ISAR1, APA, PauthFeat_1);
+    t = FIELD_DP64(t, ID_AA64ISAR1, API, 1);
     t = FIELD_DP64(t, ID_AA64ISAR1, JSCVT, 1);    /* FEAT_JSCVT */
     t = FIELD_DP64(t, ID_AA64ISAR1, FCMA, 1);     /* FEAT_FCMA */
     t = FIELD_DP64(t, ID_AA64ISAR1, LRCPC, 2);    /* FEAT_LRCPC2 */