Subject: Re: [PATCH v11 16/40] arm64/sme: Implement streaming SVE context switching

From: Catalin Marinas <[email-masked]>
Date: Tue, 22 Feb 2022 12:53:11 +0000

On Mon, Feb 07, 2022 at 03:20:45PM +0000, Mark Brown wrote:
> When in streaming mode we need to save and restore the streaming mode
> SVE register state rather than the regular SVE register state. This uses
> the streaming mode vector length and omits FFR but is otherwise identical,
> if TIF_SVE is enabled when we are in streaming mode then streaming mode
> takes precedence.
> 
> This does not handle use of streaming SVE state with KVM, ptrace or
> signals. This will be updated in further patches.

I think I get this but a state diagram somewhere would help ;).

IIUC you don't disable SM on a context switch, you just leave it in
place until a task_fpsimd_load(). It shouldn't be a problem as
kernel_neon_begin() disables it anyway.

Reviewed-by: Catalin Marinas <[email-masked]>

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