system/arm/cpu-features.rst

57 optional SVE vector lengths (see "SVE CPU Properties").  While with TCG
58 all SVE vector lengths can be supported, when KVM is in use it's more
88     vector lengths::
160 The example above disables the PMU and enables the first two SVE vector
164 defaults, it would seem we need to disable many SVE vector lengths, rather
166 disabling many SVE vector lengths would be quite verbose, the ``sve<N>`` CPU
234 is used to enable or disable specific vector lengths, where ``N`` is the
237 Constraints" below.  Additionally, as we want all supported vector lengths
246   1) At least one vector length must be enabled when ``sve`` is enabled.
248   2) If a vector length ``N`` is enabled, then, when KVM is enabled, all
249      smaller, host supported vector lengths must also be enabled.  If
250      KVM is not enabled, then only all the smaller, power-of-two vector
252      vector lengths up to 512-bits (128, 256, 384, 512), then if ``sve512``
253      is enabled, the 128-bit vector length, 256-bit vector length, and
254      384-bit vector length must also be enabled. Without KVM, the 384-bit
255      vector length would not be required.
257   3) If KVM is enabled then only vector lengths that the host CPU type
264   1) If SVE is disabled (``sve=off``), then which SVE vector lengths
266      SVE feature is disabled and that disables all vector lengths for
270      is provided and there are explicitly enabled vector lengths, then
274      provided, then all supported vector lengths are enabled, which when
276      when KVM is in use, it means all vector lengths supported by the host
280      disable the last enabled vector length (see constraint (1) of "SVE
283   4) If one or more vector lengths have been explicitly enabled and at
293      generated when attempting to enable any vector lengths not supported
298      CPU properties are set ``on``, then the specified vector lengths are
300      When KVM is not enabled, disabling a power-of-two vector length also
301      disables all vector lengths larger than the power-of-two length.
302      When KVM is enabled, then disabling any supported vector length also
303      disables all larger vector lengths (see constraint (2) of "SVE CPU
312   9) If SVE was disabled (``sve=off``), allowing all vector lengths to be
316      enable at least one vector length prior to enabling SVE.
325   2) Implicitly enable all vector lengths for the ``max`` CPU type::
329   3) When KVM is enabled, implicitly enable all host CPU supported vector
334   4) Only enable the 128-bit vector length::
338   5) Disable the 512-bit vector length and all larger vector lengths,
344   6) Enable the 128-bit, 256-bit, and 512-bit vector lengths::
348   7) The same as (6), but since the 128-bit and 256-bit vector
349      lengths are required for the 512-bit vector length to be enabled,
358   9) Force errors regarding the last vector length::
367 vector lengths which developers may find useful in order to avoid overly
368 verbose command lines.  However, the recommended way to select vector
379   2) Implicitly enable all vector lengths for the ``max`` CPU type::
383   3) Only enable the 256-bit vector length::
387   3) Enable the 256-bit and 1024-bit vector lengths::
391   4) Disable the 512-bit vector length.  This results in all the other
397 SVE User-mode Default Vector Length Property
400 For qemu-aarch64, the cpu property ``sve-default-vector-length=N`` is
404 If not specified, the default vector length is 64.
406 If the default length is larger than the maximum vector length enabled,
407 the actual vector length will be reduced.  Note that the maximum vector
410 If this property is set to ``-1`` then the default vector length
418 used to enable or disable specific vector lengths.  Finally,
425 At least one vector length must be enabled when ``sme`` is enabled,
426 and all vector lengths must be powers of 2.  The maximum vector
428 additional constraints on the set of vector lengths supported by SME.
430 SME User-mode Default Vector Length Property
433 For qemu-aarch64, the cpu property ``sme-default-vector-length=N`` is
437 If not specified, the default vector length is 32.
439 As with ``sve-default-vector-length``, if the default length is larger
440 than the maximum vector length enabled, the actual vector length will
441 be reduced.  If this property is set to ``-1`` then the default vector