linux-kernel - Re: [RFC PATCH v3 6/8] x86/pti: don't mark the user PGD with _PAGE

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Message-ID: <c23cc663-9bbf-f5a1-7182-7995b4528403@linux.intel.com>
Date:   Fri, 23 Feb 2018 11:30:58 -0800
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        "Woodhouse, David" <dwmw@...zon.co.uk>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Willy Tarreau <w@....eu>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Brian Gerst <brgerst@...il.com>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Kees Cook <keescook@...omium.org>
Subject: Re: [RFC PATCH v3 6/8] x86/pti: don't mark the user PGD with
 _PAGE_NX.

On 02/23/2018 09:58 AM, Konrad Rzeszutek Wilk wrote:
>> We also need to clear the RSB on vmexit, as documented. And if we
>> really want 100% support for retpoline on SKL+ instead of saying "use
>> IBRS if you're paranoid", then there are a few more cases where we need
>> to stuff it to avoid underflow (which is the same operation, but Arjan
>> insists we should differentiate the two, which is reasonable enough).
> Are these cases documented somewhere along with what approaches are taken?

Some of them are documented here: https://goo.gl/pXbvBE