target/arm: Enable FEAT_Spec_FPACC for -cpu max

FEAT_Spec_FPACC is a feature describing speculative behaviour in the
event of a PAC authontication failure when FEAT_FPACCOMBINE is
implemented.  FEAT_Spec_FPACC means that the speculative use of
pointers processed by a PAC Authentication is not materially
different in terms of the impact on cached microarchitectural state
(caches, TLBs, etc) between passing and failing of the PAC
Authentication.

QEMU doesn't do speculative execution, so we can advertise
this feature.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20240418152004.2106516-6-peter.maydell@linaro.org

diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
index 307539cff919e8636349cd03aa5a9534689e715a..7fcea54d8dbe882efa2cd934c16c6ab5d7888b58 100644 (file)
--- a/docs/system/arm/emulation.rst
+++ b/docs/system/arm/emulation.rst
@@ -61,6 +61,7 @@ the following architecture extensions:
 - FEAT_FP16 (Half-precision floating-point data processing)
 - FEAT_FPAC (Faulting on AUT* instructions)
 - FEAT_FPACCOMBINE (Faulting on combined pointer authentication instructions)
+- FEAT_FPACC_SPEC (Speculative behavior of combined pointer authentication instructions)
 - FEAT_FRINTTS (Floating-point to integer instructions)
 - FEAT_FlagM (Flag manipulation instructions v2)
 - FEAT_FlagM2 (Enhancements to flag manipulation instructions)

diff --git a/target/arm/tcg/cpu64.c b/target/arm/tcg/cpu64.c
index ebb585afd85cbdf3717f358e7954644f6ab0dc79..443cffe3a857d0743aa6d4f60828374472a63251 100644 (file)
--- a/target/arm/tcg/cpu64.c
+++ b/target/arm/tcg/cpu64.c
@@ -1217,6 +1217,10 @@ void aarch64_max_tcg_initfn(Object *obj)
     t = FIELD_DP64(t, ID_AA64MMFR2, E0PD, 1);     /* FEAT_E0PD */
     cpu->isar.id_aa64mmfr2 = t;
 
+    t = cpu->isar.id_aa64mmfr3;
+    t = FIELD_DP64(t, ID_AA64MMFR3, SPEC_FPACC, 1); /* FEAT_FPACC_SPEC */
+    cpu->isar.id_aa64mmfr3 = t;
+
     t = cpu->isar.id_aa64zfr0;
     t = FIELD_DP64(t, ID_AA64ZFR0, SVEVER, 1);
     t = FIELD_DP64(t, ID_AA64ZFR0, AES, 2);       /* FEAT_SVE_PMULL128 */