Re: [PATCH 0/3] arm64: cpufeature: Add filter function to control

Hi Srinivas,

On 2021-01-09 00:29, Srinivas Ramana wrote:

This patchset adds a control function for cpufeature framework
so that the feature can be controlled at runtime.

Defer PAC on boot core and use the filter function added to disable
PAC from command line. This will help toggling the feature on systems
that do not support PAC or where PAC needs to be disabled at runtime,
without modifying the core kernel.

The idea of adding the filter function for cpufeature is taken from
https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-25-catalin.marinas@arm.com/ (local)
https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-24-catalin.marinas@arm.com/ (local)

Srinivas Ramana (3):
  arm64: Defer enabling pointer authentication on boot core
  arm64: cpufeature: Add a filter function to cpufeature
  arm64: Enable control of pointer authentication using early param

 Documentation/admin-guide/kernel-parameters.txt |  6 +++
 arch/arm64/include/asm/cpufeature.h             |  8 +++-
 arch/arm64/include/asm/pointer_auth.h           | 10 +++++
 arch/arm64/include/asm/stackprotector.h         |  1 +
 arch/arm64/kernel/cpufeature.c                  | 53 
+++++++++++++++++++------
 arch/arm64/kernel/head.S                        |  4 --
 6 files changed, 64 insertions(+), 18 deletions(-)

I've been working for some time on a similar series to allow a feature
set to be disabled during the early boot phase, initially to prevent
booting a kernel with VHE, but the mechanism is generic enough to
deal with most architectural features.

I took the liberty to lift your first patch and to add it to my 
series[1],
further allowing PAuth to be disabled at boot time on top of BTI and 
VHE.

I'd appreciate your comments on this.

Thanks,

         M.

[1] https://lore.kernel.org/r/20210111132811.2455113-1-maz@kernel.org (local)
-- 
Jazz is not dead. It just smells funny...

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