[PATCH v11 17/40] arm64/sme: Implement ZA context switching

[Catalin Marinas]

On Mon, Feb 07, 2022 at 03:20:46PM +0000, Mark Brown wrote:
> 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 at kernel.org>

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>