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Message-ID: <c028d65d-27c3-826a-b16c-407e9cf48aac@codeaurora.org>
Date: Wed, 13 Jan 2021 23:15:47 -0800
From: Srinivas Ramana <sramana@...eaurora.org>
To: Marc Zyngier <maz@...nel.org>
Cc: catalin.marinas@....com, will@...nel.org, pajay@....qualcomm.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 0/3] arm64: cpufeature: Add filter function to control
Hi Marc,
On 1/11/2021 5:40 AM, Marc Zyngier wrote:
> 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/
>>
>> https://lore.kernel.org/linux-arm-kernel/20200515171612.1020-24-catalin.marinas@arm.com/
>>
>>
>> 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 for sending this series. It seems to be more flexible compared
you what we did.
Following your discussion on allowing EXACT ftr_reg values.
Btw, do you have plan to add MTE in similar lines to control the feature?
We may be needing this on some systems.
>
> Thanks,
>
> M.
>
> [1] https://lore.kernel.org/r/20210111132811.2455113-1-maz@kernel.org
Thanks,
-- Srinivas R
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