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

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Date:   Mon, 30 Nov 2020 10:20:04 -0800
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Marc Zyngier <maz@...nel.org>,
        Rongwei Wang <rongwei.wang@...ux.alibaba.com>
Cc:     catalin.marinas@....com, 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 11/30/20 10:05 AM, Marc Zyngier wrote:
> On 2020-11-30 17:48, Rongwei Wang wrote:
> 
>> The interfaces of this module is same as MSR module in user space, and to solve
>> the problem that ARM platform has no similar MSR module. Using this interface,
>> we did some pressure tests to test the stability and security of MSR driver. The
>> test results show that the driver will not cause system panic if various
>> illegal values and multithreading concurrent access are passed through the
>> interface.
> 
> It would certainly help if you described what problem you are trying
> to solve here. In general, giving userspace access to random system
> registers is a pretty bad idea.
> 
> Are you trying to validate a CPU? a hypervisor? Or is it just a fun way
> to check how many things you can poke before something catches fire?

I agree with the requests for justification.

Rongwei mentions that this driver functions the same as the
x86 platform MSR driver.  This one uses /dev.
I thought that the x86 driver used /sys, but I could be wrong.

Do we (or not) want cross-platform compatabilities?

Regarding permissions, /dev or /sys files have permission settings.
They don't have to be world-readable.


-- 
~Randy