linux-kernel - Re: [RFC 00/10] Process-local memory allocations for hiding KVM secrets

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Date:   Wed, 12 Jun 2019 12:55:38 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Marius Hillenbrand <mhillenb@...zon.de>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        linux-mm@...ck.org, Alexander Graf <graf@...zon.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        the arch/x86 maintainers <x86@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [RFC 00/10] Process-local memory allocations for hiding KVM
 secrets

On 6/12/19 10:08 AM, Marius Hillenbrand wrote:
> This patch series proposes to introduce a region for what we call
> process-local memory into the kernel's virtual address space. 

It might be fun to cc some x86 folks on this series.  They might have
some relevant opinions. ;)

A few high-level questions:

Why go to all this trouble to hide guest state like registers if all the
guest data itself is still mapped?

Where's the context-switching code?  Did I just miss it?

We've discussed having per-cpu page tables where a given PGD is only in
use from one CPU at a time.  I *think* this scheme still works in such a
case, it just adds one more PGD entry that would have to context-switched.