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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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docs/system/arm/emulation.rst
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@ -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)