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KVM: arm64: Specify hypercall ABI for retrieving target implementations
If the Guest requires migration to multiple targets, these hypercalls will provide a way to retrieve the target CPU implementations from the user space VMM. Subsequent patch will use this to enable the associated errata. Suggested-by: Oliver Upton <oliver.upton@linux.dev> Suggested-by: Marc Zyngier <maz@kernel.org> Reviewed-by: Cornelia Huck <cohuck@redhat.com> Reviewed-by: Sebastian Ott <sebott@redhat.com> Signed-off-by: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com> Link: https://lore.kernel.org/r/20250221140229.12588-3-shameerali.kolothum.thodi@huawei.com Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
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‎Documentation/virt/kvm/arm/hypercalls.rst

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@@ -142,3 +142,62 @@ region is equal to the memory protection granule advertised by
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| | | +---------------------------------------------+
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| | | | ``INVALID_PARAMETER (-3)`` |
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+---------------------+----------+----+---------------------------------------------+
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``ARM_SMCCC_VENDOR_HYP_KVM_DISCOVER_IMPL_VER_FUNC_ID``
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-------------------------------------------------------
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Request the target CPU implementation version information and the number of target
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implementations for the Guest VM.
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+---------------------+-------------------------------------------------------------+
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| Presence: | Optional; KVM/ARM64 Guests only |
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+---------------------+-------------------------------------------------------------+
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| Calling convention: | HVC64 |
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+---------------------+----------+--------------------------------------------------+
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| Function ID: | (uint32) | 0xC6000040 |
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+---------------------+----------+--------------------------------------------------+
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| Arguments: | None |
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+---------------------+----------+----+---------------------------------------------+
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| Return Values: | (int64) | R0 | ``SUCCESS (0)`` |
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| | | +---------------------------------------------+
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| | | | ``NOT_SUPPORTED (-1)`` |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R1 | Bits [63:32] Reserved/Must be zero |
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| | | +---------------------------------------------+
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| | | | Bits [31:16] Major version |
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| | | +---------------------------------------------+
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| | | | Bits [15:0] Minor version |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R2 | Number of target implementations |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R3 | Reserved / Must be zero |
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+---------------------+----------+----+---------------------------------------------+
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``ARM_SMCCC_VENDOR_HYP_KVM_DISCOVER_IMPL_CPUS_FUNC_ID``
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-------------------------------------------------------
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Request the target CPU implementation information for the Guest VM. The Guest kernel
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will use this information to enable the associated errata.
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+---------------------+-------------------------------------------------------------+
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| Presence: | Optional; KVM/ARM64 Guests only |
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+---------------------+-------------------------------------------------------------+
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| Calling convention: | HVC64 |
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+---------------------+----------+--------------------------------------------------+
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| Function ID: | (uint32) | 0xC6000041 |
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+---------------------+----------+----+---------------------------------------------+
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| Arguments: | (uint64) | R1 | selected implementation index |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R2 | Reserved / Must be zero |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R3 | Reserved / Must be zero |
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+---------------------+----------+----+---------------------------------------------+
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| Return Values: | (int64) | R0 | ``SUCCESS (0)`` |
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| | | +---------------------------------------------+
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| | | | ``INVALID_PARAMETER (-3)`` |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R1 | MIDR_EL1 of the selected implementation |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R2 | REVIDR_EL1 of the selected implementation |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R3 | AIDR_EL1 of the selected implementation |
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+---------------------+----------+----+---------------------------------------------+

‎include/linux/arm-smccc.h

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#define ARM_SMCCC_KVM_FUNC_PKVM_RESV_62 62
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#define ARM_SMCCC_KVM_FUNC_PKVM_RESV_63 63
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/* End of pKVM hypercall range */
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#define ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_VER 64
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#define ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_CPUS 65
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#define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
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#define ARM_SMCCC_KVM_NUM_FUNCS 128
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ARM_SMCCC_OWNER_VENDOR_HYP, \
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ARM_SMCCC_KVM_FUNC_MMIO_GUARD)
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#define ARM_SMCCC_VENDOR_HYP_KVM_DISCOVER_IMPL_VER_FUNC_ID \
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ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
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ARM_SMCCC_SMC_64, \
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ARM_SMCCC_OWNER_VENDOR_HYP, \
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ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_VER)
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#define ARM_SMCCC_VENDOR_HYP_KVM_DISCOVER_IMPL_CPUS_FUNC_ID \
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ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
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ARM_SMCCC_SMC_64, \
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ARM_SMCCC_OWNER_VENDOR_HYP, \
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ARM_SMCCC_KVM_FUNC_DISCOVER_IMPL_CPUS)
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/* ptp_kvm counter type ID */
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#define KVM_PTP_VIRT_COUNTER 0
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#define KVM_PTP_PHYS_COUNTER 1

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