Commit d198c77b authored by Mark Brown's avatar Mark Brown Committed by Will Deacon
Browse files

arm64: Document boot requirements for FEAT_SME_FA64 



The EAC1 release of the SME specification adds the FA64 feature which
requires enablement at higher ELs before lower ELs can use it. Document
what we require from higher ELs in our boot requirements.

Signed-off-by: default avatarMark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20211026111802.12853-1-broonie@kernel.org


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent de56379f

Documentation/arm64/booting.rst

+10 −0
Original line number Diff line number Diff line
@@ -340,6 +340,16 @@ Before jumping into the kernel, the following conditions must be met: 
    - SMCR_EL2.LEN must be initialised to the same value for all CPUs the

      kernel will execute on.



  For CPUs with the Scalable Matrix Extension FA64 feature (FEAT_SME_FA64)



  - If EL3 is present:



    - SMCR_EL3.FA64 (bit 31) must be initialised to 0b1.



 - If the kernel is entered at EL1 and EL2 is present:



    - SMCR_EL2.FA64 (bit 31) must be initialised to 0b1.



The requirements described above for CPU mode, caches, MMUs, architected

timers, coherency and system registers apply to all CPUs.  All CPUs must

enter the kernel in the same exception level.  Where the values documented