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

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Message-Id: <A542C98B-486C-4849-9DAC-2355F0F89A20@amacapital.net>
Date:   Wed, 12 Jun 2019 13:27:04 -0700
From:   Andy Lutomirski <luto@...capital.net>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Marius Hillenbrand <mhillenb@...zon.de>, kvm@...r.kernel.org,
        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 Jun 12, 2019, at 12:55 PM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
>> 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.

Fair warning: Linus is on record as absolutely hating this idea. He might change his mind, but it’s an uphill battle.