Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752292AbbKKQFU (ORCPT ); Wed, 11 Nov 2015 11:05:20 -0500 Received: from mail.skyhub.de ([78.46.96.112]:49128 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752176AbbKKQFT (ORCPT ); Wed, 11 Nov 2015 11:05:19 -0500 Date: Wed, 11 Nov 2015 17:05:15 +0100 From: Borislav Petkov To: Andy Lutomirski Cc: LKML , Andy Lutomirski , "H. Peter Anvin" , Ingo Molnar , Linus Torvalds , Peter Zijlstra , Thomas Gleixner Subject: Re: [RFC PATCH] x86/cpu: Fix MSR value truncation issue Message-ID: <20151111160515.GH22512@pd.tnic> References: <1446226105-13384-1-git-send-email-bp@alien8.de> <20151111123158.GF22512@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1280 Lines: 36 On Wed, Nov 11, 2015 at 07:50:04AM -0800, Andy Lutomirski wrote: > Not terribly surprising :) Someone (I forget who) told me that 32-bit > SYSCALL (native 32-bit, not compat) was so full of errata that it was > unusable. Even without errata, I don't really see how it would work > well No, showstopper appears much earlier: it is only supported on AMD. Which would mean, yet another vendor special-handling. And I don't think it's worth it. Yeah, yeah, it might still be faster than SYSENTER, but 32-bit?! Srsly?! I'm surprised that thing still builds even. :-) > -- there's no MSR_SYSCALL_MASK, Of course there is: MSRC000_0084 SYSCALL Flag Mask (SYSCALL_FLAG_MASK): 31:0 - Mask: SYSCALL flag mask. Read-write. Reset: 0000_0000h. This register holds the EFLAGS mask used by the SYSCALL instruction. 1=Clear the corresponding EFLAGS bit when executing the SYSCALL instruction. Intel has that too, except again, no SYSCALL in legacy mode on Intel. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/