tree 7566d580e8dee5400b5815dd88dbb28e55385f9f
parent 4ba37e52b2ec920c5b8beb1f1ea200254f8c7546
author Andre Przywara <andre.przywara@arm.com> 1723219462 +0100
committer André Przywara <andre.przywara@arm.com> 1730908332 +0100

feat(cpufeat): add ENABLE_FEAT_LS64_ACCDATA

Armv8.6 introduced the FEAT_LS64 extension, which provides a 64 *byte*
store instruction. A related instruction is ST64BV0, which will replace
the lowest 32 bits of the data with a value taken from the ACCDATA_EL1
system register (so that EL0 cannot alter them).
Using that ST64BV0 instruction and accessing the ACCDATA_EL1 system
register is guarded by two SCR_EL3 bits, which we should set to avoid a
trap into EL3, when lower ELs use one of those.

Add the required bits and pieces to make this feature usable:
- Add the ENABLE_FEAT_LS64_ACCDATA build option (defaulting to 0).
- Add the CPUID and SCR_EL3 bit definitions associated with FEAT_LS64.
- Add a feature check to check for the existing four variants of the
  LS64 feature and detect future extensions.
- Add code to save and restore the ACCDATA_EL1 register on
  secure/non-secure context switches.
- Enable the feature with runtime detection for FVP and Arm FPGA.

Please note that the *basic* FEAT_LS64 feature does not feature any trap
bits, it's only the addition of the ACCDATA_EL1 system register that
adds these traps and the SCR_EL3 bits.

Change-Id: Ie3e2ca2d9c4fbbd45c0cc6089accbb825579138a
Signed-off-by: Andre Przywara <andre.przywara@arm.com>