system/arm/cpu-features.rst

16 As not all CPU types support all optional CPU features, then whether or
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
58 all SVE vector lengths can be supported, when KVM is in use it's more
60 all.)
87 (4) Let's disable ``sve`` and see what happens to all the optional SVE
100 As expected they are now all ``false``.
114 when attempting to change all features at once an error could occur
116 all at once doesn't generate an error, because a feature's dependencies
119 attempt to make their desired changes all at once in order to ensure the
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
133 do if we want to launch guests without all the host's CPU features enabled.
139 expanded.  This restriction is necessary as it's not possible to know all
189   the virtual and physical counters diverging.  All timekeeping based
240 Constraints" below.  Additionally, as we want all supported vector lengths
242 lines (command lines full of ``sve<N>=off``, for all ``N`` not wanted), we
251   2) If a vector length ``N`` is enabled, then, when KVM is enabled, all
253      KVM is not enabled, then only all the smaller, power-of-two vector
254      lengths must be enabled.  E.g. with KVM if the host supports all
269      SVE feature is disabled and that disables all vector lengths for
277      provided, then all supported vector lengths are enabled, which when
279      when KVM is in use, it means all vector lengths supported by the host
304      disables all vector lengths larger than the power-of-two length.
306      disables all larger vector lengths (see constraint (2) of "SVE CPU
310      are enabled and all unspecified lengths default to disabled, except
315   9) If SVE was disabled (``sve=off``), allowing all vector lengths to be
328   2) Implicitly enable all vector lengths for the ``max`` CPU type::
332   3) When KVM is enabled, implicitly enable all host CPU supported vector
341   5) Disable the 512-bit vector length and all larger vector lengths,
342      since 512 is a power-of-two.  This results in all the smaller,
382   2) Implicitly enable all vector lengths for the ``max`` CPU type::
394   4) Disable the 512-bit vector length.  This results in all the other
429 and all vector lengths must be powers of 2.  The maximum vector