From d198c77b7fab13d4def83c038807f6967f857acc Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Tue, 26 Oct 2021 12:18:02 +0100 Subject: 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: Mark Brown Link: https://lore.kernel.org/r/20211026111802.12853-1-broonie@kernel.org Signed-off-by: Will Deacon --- Documentation/arm64/booting.rst | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'Documentation/arm64') diff --git a/Documentation/arm64/booting.rst b/Documentation/arm64/booting.rst index 3f9d86557c5e..52d060caf8bb 100644 --- a/Documentation/arm64/booting.rst +++ b/Documentation/arm64/booting.rst @@ -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 -- cgit v1.2.3-59-g8ed1b