linux-kernel - RE: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Wed, 10 Jan 2018 02:47:01 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     "Van De Ven, Arjan" <arjan.van.de.ven@...el.com>
cc:     "Hansen, Dave" <dave.hansen@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...e.de>,
        "Raj, Ashok" <ashok.raj@...el.com>
Subject: RE: [patch RFC 1/5] x86/CPU: Sync CPU feature flags late

On Wed, 10 Jan 2018, Van De Ven, Arjan wrote:
> > In other words, if you use late microcode loading for getting IBRS, you
> > don't get ALTERNATIVE patching and its benefits?
> > 
> > I'll also profess some microcode ignorance here.  Is "late microcode
> > patching" *all* of the stuff we do from the OS, or do we have early and
> > late Linux loading in addition to what the BIOS can do?
> 
> the early boot loader level stuff is much better generally (but does not
> work when the microcode comes out after the system booted... like really
> long uptimes)

That stuff indeed would be way simpler w/o the late support, but the fact
that the microcode for this might reach the user way later than the kernel
support makes it almost a must to support the late loading.

Thanks,

	tglx