tree f5c437cd6e6c4cd3f0f5a8d7c0e690d5b358f6a2
parent af7167d6d2675f3343eff3ad6c9b4a8e30122e2c
author Mark Brown <broonie@kernel.org> 1650367343 +0100
committer Catalin Marinas <catalin.marinas@arm.com> 1650649862 +0100

arm64/sme: Implement ZA context switching

Allocate space for storing ZA on first access to SME and use that to save
and restore ZA state when context switching. We do this by using the vector
form of the LDR and STR ZA instructions, these do not require streaming
mode and have implementation recommendations that they avoid contention
issues in shared SMCU implementations.

Since ZA is architecturally guaranteed to be zeroed when enabled we do not
need to explicitly zero ZA, either we will be restoring from a saved copy
or trapping on first use of SME so we know that ZA must be disabled.

Signed-off-by: Mark Brown <broonie@kernel.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/20220419112247.711548-16-broonie@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>