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Date:   Fri, 12 Jul 2019 21:06:20 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Alexandre Chartre <alexandre.chartre@oracle.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Dave Hansen <dave.hansen@intel.com>, pbonzini@redhat.com,
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        konrad.wilk@oracle.com, jan.setjeeilers@oracle.com,
        liran.alon@oracle.com, jwadams@google.com, graf@amazon.de,
        rppt@linux.vnet.ibm.com, Paul Turner <pjt@google.com>
Subject: Re: [RFC v2 00/27] Kernel Address Space Isolation
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On Fri, Jul 12, 2019 at 06:37:47PM +0200, Alexandre Chartre wrote:
> On 7/12/19 5:16 PM, Thomas Gleixner wrote:

> > Right. If we decide to expose more parts of the kernel mappings then that's
> > just adding more stuff to the existing user (PTI) map mechanics.
> 
> If we expose more parts of the kernel mapping by adding them to the existing
> user (PTI) map, then we only control the mapping of kernel sensitive data but
> we don't control user mapping (with ASI, we exclude all user mappings).
> 
> How would you control the mapping of userland sensitive data and exclude them
> from the user map? Would you have the application explicitly identify sensitive
> data (like Andy suggested with a /dev/xpfo device)?

To what purpose do you want to exclude userspace from the kernel
mapping; that is, what are you mitigating against with that?