linux-kernel - Re: [PATCH 0/3] arm64:msr: Add MSR driver

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Message-Id: <82A9ACCC-9A2A-48A7-939A-6E13E13EA465@linux.alibaba.com>
Date:   Thu, 3 Dec 2020 20:22:43 +0800
From:   Rongwei Wang <rongwei.wang@...ux.alibaba.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     catalin.marinas@....com, Will Deacon <will@...nel.org>,
        bjorn.andersson@...aro.org, shawnguo@...nel.org, gshan@...hat.com,
        geert+renesas@...der.be, Anson.Huang@....com, masahiroy@...nel.org,
        michael@...le.cc, krzk@...nel.org, linux-kernel@...r.kernel.org,
        vkoul@...nel.org, olof@...om.net, vincenzo.frascino@....com,
        ardb@...nel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/3] arm64:msr: Add MSR driver



> On Dec 3, 2020, at 7:45 PM, Marc Zyngier <maz@...nel.org> wrote:
> 
> On 2020-12-03 11:25, Rongwei Wang wrote:
>>> 2020年12月3日 下午4:35，Marc Zyngier <maz@...nel.org> 写道：
> 
> [...]
> 
>>> But what does it mean to change random system registers while the kernel
>>> itself is using them in parallel? All you are introducing is a bunch of
>>> uncontrolled, unexpected, and possibly fatal side effects.
>> This problem exists when writing to a register, but it does not exist
>> when reading a register.
> 
> If you're not aware that the ARM architecture does have system registers
> with read side-effects, you really shouldn't be writing this code.
Thanks, Does it make sense to put this feature in the drivers/ directory, likes misc drivers? Whether it can exist as a debugging tool in kernel or not?
When debugging, then enables CONFIG_ARM64_MSR or CONFIG_ARM64_MSR_DEBUG.
> 
>        M.
> -- 
> Jazz is not dead. It just smells funny…
Thanks,
Rongwei Wang.