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Re: [PATCH v3 12/21] linux-user/aarch64: Implement PR_TAGGED_ADDR_ENABLE


From: Peter Maydell
Subject: Re: [PATCH v3 12/21] linux-user/aarch64: Implement PR_TAGGED_ADDR_ENABLE
Date: Fri, 22 Jan 2021 12:02:07 +0000

On Fri, 22 Jan 2021 at 11:53, Peter Maydell <peter.maydell@linaro.org> wrote:
> The kernel's "untagged_addr()" implementation:
> https://elixir.bootlin.com/linux/latest/source/arch/arm64/include/asm/memory.h#L203
> slightly confusingly does "untag the addr if it's in the userspace
> half, leave the tag bits alone if in the kernel half".

...and a kernel person has just explained to me the rationale:
TBI is always enabled for userspace and never for the kernel,
so "always clear tag bits for a userspace address, never clear
them for a kernel address" is the right behaviour. I think we
should have the same logic.

-- PMM



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