linux-kernel - Re: [RFC v4][PATCH part-1 0/7] ASI - Part I (ASI Infrastructure and PTI)

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Message-Id: <7F322031-034E-4B36-A60F-663EAA4C99C9@amacapital.net>
Date:   Tue, 12 May 2020 13:07:28 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Alexandre Chartre <alexandre.chartre@...cle.com>,
        rkrcmar@...hat.com, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, hpa@...or.com, dave.hansen@...ux.intel.com,
        luto@...nel.org, peterz@...radead.org, x86@...nel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, konrad.wilk@...cle.com,
        jan.setjeeilers@...cle.com, liran.alon@...cle.com,
        junaids@...gle.com, graf@...zon.de, rppt@...ux.vnet.ibm.com,
        kuzuno@...il.com, mgross@...ux.intel.com
Subject: Re: [RFC v4][PATCH part-1 0/7] ASI - Part I (ASI Infrastructure and PTI)


> On May 12, 2020, at 10:45 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
> On 5/4/20 7:49 AM, Alexandre Chartre wrote:
>> This version 4 of the kernel Address Space Isolation (ASI) RFC. I have
>> broken it down into three distinct parts:
>> 
>> - Part I: ASI Infrastructure and PTI (this part)
>> - Part II: Decorated Page-Table
>> - Part III: ASI Test Driver and CLI
>> 
>> Part I is similar to RFCv3 [3] with some small bug fixes. Parts II and III
>> extend the initial patchset: part II introduces decorated page-table in
>> order to provide convenient page-table management functions, and part III
>> provides a driver and CLI for testing ASI (using parts I and II).
> 
> These look interesting.  I haven't found any holes in your methods,
> although the interrupt depth tracking worries me a bit.  I tried and
> failed to do a similar thing with PTI in the NMI path, but you might
> have just bested me there. :)
> 
> It's very interesting that you've been able to implement PTI underneath
> all of this, and the "test driver" is really entertaining!
> 
> That said, this is working in some of the nastiest corners of the x86
> code and this is going to take quite an investment to get reviewed.  I'm
> not *quite* sure it's all worth it.
> 
> So, this isn't being ignored, I'm just not quite sure what to do with
> it, yet.

I’m going to wait until the dust settles on tglx’s big entry rework before I look at this.