linux-kernel - Re: [PATCH 25/43] x86/mm/kaiser: Unmap kernel from userspace page tables (core patch)

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Date:   Fri, 24 Nov 2017 08:33:09 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 25/43] x86/mm/kaiser: Unmap kernel from userspace page
 tables (core patch)

On 11/24/2017 04:16 AM, Peter Zijlstra wrote:
> On Fri, Nov 24, 2017 at 10:14:30AM +0100, Ingo Molnar wrote:
>> +The minimalistic kernel portion of the user page tables try to
>> +map only what is needed to enter/exit the kernel such as the
>> +entry/exit functions themselves and the interrupt descriptor
>> +table (IDT).  
> 
>                 There are a few unnecessary things that get mapped
>> +such as the first C function when entering an interrupt (see
>> +comments in kaiser.c).
> 
> If I understood Andy's patches correctly, this should no longer be
> required. Is this text still correct?

It is out of date.  We were able to remove the irq handler mappings.