linux-kernel - Re: [PATCH 00/31 v2] PTI support for x86

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Message-ID: <1518387160.3979.10.camel@HansenPartnership.com>
Date:   Sun, 11 Feb 2018 14:12:40 -0800
From:   James Bottomley <James.Bottomley@...senPartnership.com>
To:     Andy Lutomirski <luto@...capital.net>,
        Mark D Rustad <mrustad@...il.com>
Cc:     Adam Borowski <kilobyte@...band.pl>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>, Jiri Kosina <jkosina@...e.cz>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Brian Gerst <brgerst@...il.com>,
        David Laight <David.Laight@...lab.com>,
        Denys Vlasenko <dvlasenk@...hat.com>,
        Eduardo Valentin <eduval@...zon.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Will Deacon <will.deacon@....com>,
        "Liguori, Anthony" <aliguori@...zon.com>,
        Daniel Gruss <daniel.gruss@...k.tugraz.at>,
        Hugh Dickins <hughd@...gle.com>,
        Kees Cook <keescook@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH 00/31 v2] PTI support for x86_32

On Sun, 2018-02-11 at 11:42 -0800, Andy Lutomirski wrote:
> 
> On Feb 11, 2018, at 9:40 AM, Mark D Rustad <mrustad@...il.com> wrote:
> 
> > 
> > > 
> > > On Feb 11, 2018, at 2:59 AM, Adam Borowski <kilobyte@...band.pl>
> > > wrote:
> > > 
> > > > 
> > > > Does Debian make it easy to upgrade to a 64-bit kernel if you
> > > > have a
> > > > 32-bit install?
> > > 
> > > Quite easy, yeah.  Crossgrading userspace is not for the faint of
> > > the heart,
> > > but changing just the kernel is fine.
> > 
> > ISTR that iscsi doesn't work when running a 64-bit kernel with a
> > 32-bit userspace. I remember someone offered kernel patches to fix
> > it, but I think they were rejected. I haven't messed with that
> > stuff in many years, so perhaps the userspace side now has
> > accommodation for it. It might be something to check on.
> > 
> 
> At the risk of suggesting heresy, should we consider removing x86_32
> support at some point?

Hey, my cloud server is 32 bit:

bedivere:~# cat /proc/cpuinfo 
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 15
model		: 2
model name	: Intel(R) Pentium(R) 4 CPU 2.80GHz
stepping	: 9
microcode	: 0x2e
cpu MHz		: 2813.464
[...]

I suspect a lot of people are in the same position: grandfathered in on
an old hosting plan, but not really willing to switch to a new 64 bit
box because the monthly cost about doubles and nothing it does is
currently anywhere up to (let alone over) the capacity of the single
686 processor.

The thing which is making me consider it is actually getting a TPM to
protect the private keys, but doubling the monthly cost is still a huge
disincentive.

James