FEAT_HPMN0 is a small feature which defines that it is valid for
MDCR_EL2.HPMN to be set to 0, meaning "no PMU event counters provided
to an EL1 guest" (previously this setting was reserved). QEMU's
implementation almost gets HPMN == 0 right, but we need to fix
one check in pmevcntr_is_64_bit(). That is enough for us to
advertise the feature in the 'max' CPU.
(We don't need to make the behaviour conditional on feature
presence, because the FEAT_HPMN0 behaviour is within the range
of permitted UNPREDICTABLE behaviour for a non-FEAT_HPMN0
implementation.)
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230921185445.3339214-1-peter.maydell@linaro.org
---
docs/system/arm/emulation.rst | 1 +
target/arm/helper.c | 2 +-
target/arm/tcg/cpu32.c | 4 ++++
target/arm/tcg/cpu64.c | 1 +
4 files changed, 7 insertions(+), 1 deletion(-)
diff --git a/docs/system/arm/emulation.rst b/docs/system/arm/emulation.rst
index 965cbf84c51..47fd648035f 100644
--- a/docs/system/arm/emulation.rst
+++ b/docs/system/arm/emulation.rst
@@ -46,6 +46,7 @@ the following architecture extensions:
- FEAT_HCX (Support for the HCRX_EL2 register)
- FEAT_HPDS (Hierarchical permission disables)
- FEAT_HPDS2 (Translation table page-based hardware attributes)
+- FEAT_HPMN0 (Setting of MDCR_EL2.HPMN to zero)
- FEAT_I8MM (AArch64 Int8 matrix multiplication instructions)
- FEAT_IDST (ID space trap handling)
- FEAT_IESB (Implicit error synchronization event)
diff --git a/target/arm/helper.c b/target/arm/helper.c
index 01cd1474565..b29edb26af8 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -1283,7 +1283,7 @@ static bool pmevcntr_is_64_bit(CPUARMState *env, int counter)
bool hlp = env->cp15.mdcr_el2 & MDCR_HLP;
int hpmn = env->cp15.mdcr_el2 & MDCR_HPMN;
- if (hpmn != 0 && counter >= hpmn) {
+ if (counter >= hpmn) {
return hlp;
}
}
diff --git a/target/arm/tcg/cpu32.c b/target/arm/tcg/cpu32.c
index 1f918ff5375..0d5d8e307dd 100644
--- a/target/arm/tcg/cpu32.c
+++ b/target/arm/tcg/cpu32.c
@@ -89,6 +89,10 @@ void aa32_max_features(ARMCPU *cpu)
t = FIELD_DP32(t, ID_DFR0, COPSDBG, 9); /* FEAT_Debugv8p4 */
t = FIELD_DP32(t, ID_DFR0, PERFMON, 6); /* FEAT_PMUv3p5 */
cpu->isar.id_dfr0 = t;
+
+ t = cpu->isar.id_dfr1;
+ t = FIELD_DP32(t, ID_DFR1, HPMN0, 1); /* FEAT_HPMN0 */
+ cpu->isar.id_dfr1 = t;
}
/* CPU models. These are not needed for the AArch64 linux-user build. */
diff --git a/target/arm/tcg/cpu64.c b/target/arm/tcg/cpu64.c
index 68928e51272..d978aa5f7ad 100644
--- a/target/arm/tcg/cpu64.c
+++ b/target/arm/tcg/cpu64.c
@@ -1109,6 +1109,7 @@ void aarch64_max_tcg_initfn(Object *obj)
t = cpu->isar.id_aa64dfr0;
t = FIELD_DP64(t, ID_AA64DFR0, DEBUGVER, 9); /* FEAT_Debugv8p4 */
t = FIELD_DP64(t, ID_AA64DFR0, PMUVER, 6); /* FEAT_PMUv3p5 */
+ t = FIELD_DP64(t, ID_AA64DFR0, HPMN0, 1); /* FEAT_HPMN0 */
cpu->isar.id_aa64dfr0 = t;
t = cpu->isar.id_aa64smfr0;
--
2.34.1