system/arm/cpu-features.rst

1 Arm CPU Features
4 CPU features are optional features that a CPU of supporting type may
5 choose to implement or not.  In QEMU, optional CPU features have
16 As not all CPU types support all optional CPU features, then whether or
23 QEMU's support may be limited for some CPU features, only partially
29 it could work with TCG.  CPU features that are specific to KVM are
30 prefixed with "kvm-" and are described in "KVM VCPU Features".
35 Determining which CPU features are available and functional for a given
40 1. Determine which CPU features are available for the ``max`` CPU type
55 ``sve<N>`` CPU features.  We also see that all the CPU features are
56 enabled, as they are all ``true``.  (The ``sve<N>`` CPU features are all
102 (5) Let's try probing CPU features for the Cortex-A15 CPU type::
112 It's possible for features to have dependencies on other features. I.e.
114 when attempting to change all features at once an error could occur
117 are satisfied with other features, but the same feature cannot be changed
128 used.  This means the guest is provided all the same CPU features as the
130 enable all CPU features that the host has by default.  Indeed it's even
131 a bit strange to allow disabling CPU features that the host has when using
133 do if we want to launch guests without all the host's CPU features enabled.
136 affect is not only limited to specific features, as pointed out in example
151 Using CPU Features
154 After determining which CPU features are available and supported for a
170 KVM VCPU Features
173 KVM VCPU features are CPU features that are specific to KVM, such as
174 paravirt features or features that enable CPU virtualization extensions.
175 The features' CPU properties are only available when KVM is enabled and
176 are named with the prefix "kvm-".  KVM VCPU features may be probed,
177 enabled, and disabled in the same way as other CPU features.  Below is
178 the list of KVM VCPU features and their descriptions.
207 TCG VCPU Features
210 TCG VCPU features are CPU features that are specific to TCG.
211 Below is the list of TCG VCPU features and their descriptions.