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

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Date:   Fri, 9 Feb 2018 14:35:07 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Josh Poimboeuf <jpoimboe@...hat.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>, aliguori@...zon.com,
        daniel.gruss@...k.tugraz.at, hughd@...gle.com, keescook@...gle.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Waiman Long <llong@...hat.com>, Pavel Machek <pavel@....cz>,
        jroedel@...e.de
Subject: Re: [PATCH 00/31 v2] PTI support for x86_32

Hi Juergen,

On Fri, Feb 09, 2018 at 01:11:42PM +0100, Juergen Gross wrote:
> On 09/02/18 10:25, Joerg Roedel wrote:
> > XENPV is also untested from my side, but I added checks to
> > not do the stack switches in the entry-code when XENPV is
> > enabled, so hopefully it works. But someone should test it,
> > of course.
> 
> That's unfortunate. 32 bit XENPV kernel is vulnerable to Meltdown, too.
> I'll have a look whether 32 bit XENPV is still working, though.
> 
> Adding support for KPTI with Xen PV should probably be done later. :-)

Not sure how much is missing to make it work there, one point is
certainly to write the right stack into tss.sp0 for xenpv on 32bit. This
write has a check to only happen for !xenpv.

But let's first test the code as-is on XENPV and see if it still boots
:)


Thanks,

	Joerg