Re: [PATCH v8 1/3] arm64: mte: make the per-task SCTLR_EL1 field usable elsewhere

On Wed, Apr 14, 2021 at 3:10 AM Catalin Marinas [off-list ref] wrote:

On Thu, 18 Mar 2021 20:10:52 -0700, Peter Collingbourne wrote:

quoted

In an upcoming change we are going to introduce per-task SCTLR_EL1
bits for PAC. Move the existing per-task SCTLR_EL1 field out of the
MTE-specific code so that we will be able to use it from both the
PAC and MTE code paths and make the task switching code more efficient.

Applied to arm64 (for-next/pac-set-get-enabled-keys).

Peter, can you please have a look and give it a try as part of the arm64
for-next/core branch? I rebased your patches on top of the
for-next/mte-async-kernel-mode branch as this was adding more code to
mte_thread_switch(), so I kept the function for now.

Thanks.

[1/3] arm64: mte: make the per-task SCTLR_EL1 field usable elsewhere
      https://git.kernel.org/arm64/c/2f79d2fc391e
[2/3] arm64: Introduce prctl(PR_PAC_{SET,GET}_ENABLED_KEYS)
      https://git.kernel.org/arm64/c/201698626fbc
[3/3] arm64: pac: Optimize kernel entry/exit key installation code paths
      https://git.kernel.org/arm64/c/b90e483938ce

Hi Catalin,

I tested the rebased patch series on an Apple M1 under a hypervisor
with my Android forward-edge PAC prototype and it seems to work.

I think it should be possible to get rid of at least one of the ISBs
that are now on the task switch path, but let's leave that to a later
patch. The patch series looks good otherwise.

Peter