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target/arm: Implement FEAT_HPMN0

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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
This commit is contained in:
Peter Maydell 2023-09-21 19:54:45 +01:00
parent 4cdd146d8b
commit 3d80bbf1f6
4 changed files with 7 additions and 1 deletions
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4
target/arm/tcg/cpu32.c
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@ -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. */