kvm/arm/fw-pseudo-registers.rst

1 .. SPDX-License-Identifier: GPL-2.0
4 ARM firmware pseudo-registers interface
12 two different "firmware" revisions. This could cause issues if a given guest
17 In order to remedy this situation, KVM exposes a set of "firmware
18 pseudo-registers" that can be manipulated using the GET/SET_ONE_REG
28   and power-off to the guest.
30   - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set
31     (and thus has already been initialized)
32   - Returns the current PSCI version on GET_ONE_REG (defaulting to the
34   - Allows any PSCI version implemented by KVM and compatible with
36   - Affects the whole VM (even if the register view is per-vcpu)
39     Holds the state of the firmware support to mitigate CVE-2017-5715, as
47       firmware support for the workaround. The mitigation status for the
57     Holds the state of the firmware support to mitigate CVE-2018-3639, as
65       available. KVM does not offer firmware support for the workaround.
68       unknown. KVM does not offer firmware support for the workaround.
78 Bitmap Feature Firmware Registers
79 ---------------------------------
82 hypercall services in the form of a feature-bitmap to the userspace. This
89 hypercall services via GET_ONE_REG. The user-space can write-back the
96 return a -EBUSY.
98 The pseudo-firmware bitmap register are as follows:
105     Bit-0: KVM_REG_ARM_STD_BIT_TRNG_V1_0:
114     Bit-0: KVM_REG_ARM_STD_HYP_BIT_PV_TIME:
123     Bit-0: KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT
125       and ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID function-ids.
127     Bit-1: KVM_REG_ARM_VENDOR_HYP_BIT_PTP:
133     -ENOENT   Unknown register accessed.
134     -EBUSY    Attempt a 'write' to the register after the VM has started.
135     -EINVAL   Invalid bitmap written to the register.
138 .. [1] https://developer.arm.com/-/media/developer/pdf/ARM_DEN_0070A_Firmware_interfaces_for_mitiga…