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

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Date:   Thu, 03 Dec 2020 11:45:24 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Rongwei Wang <rongwei.wang@...ux.alibaba.com>
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 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.

         M.
-- 
Jazz is not dead. It just smells funny...