Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752279AbdHZIQz (ORCPT ); Sat, 26 Aug 2017 04:16:55 -0400 Received: from Galois.linutronix.de ([146.0.238.70]:43567 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751203AbdHZIQy (ORCPT ); Sat, 26 Aug 2017 04:16:54 -0400 Date: Sat, 26 Aug 2017 10:16:43 +0200 (CEST) From: Thomas Gleixner To: Boris Ostrovsky cc: LKML , Ingo Molnar , Peter Anvin , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Steven Rostedt , Juergen Gross Subject: Re: [patch V2 35/44] x86/idt: Switch early trap init to IDT tables In-Reply-To: <7e182f46-d27b-9414-fb6d-ee48906a4180@oracle.com> Message-ID: References: <20170825214648.264521964@linutronix.de> <20170825214942.983480384@linutronix.de> <7e182f46-d27b-9414-fb6d-ee48906a4180@oracle.com> User-Agent: Alpine 2.20 (DEB 67 2015-01-07) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1744 Lines: 52 On Fri, 25 Aug 2017, Boris Ostrovsky wrote: > On 08/25/2017 05:47 PM, Thomas Gleixner wrote: > > > > -/* Set of traps needed for early debugging. */ > > -void __init early_trap_init(void) > > -{ > > - /* > > - * Don't use IST to set DEBUG_STACK as it doesn't work until TSS > > - * is ready in cpu_init() <-- trap_init(). Before trap_init(), > > - * CPU runs at ring 0 so it is impossible to hit an invalid > > - * stack. Using the original stack works well enough at this > > - * early stage. DEBUG_STACK will be equipped after cpu_init() in > > - * trap_init(). > > - */ > > - set_intr_gate(X86_TRAP_DB, debug); > > - /* int3 can be called from all */ > > - set_system_intr_gate(X86_TRAP_BP, &int3); > > -#ifdef CONFIG_X86_32 > > - set_intr_gate(X86_TRAP_PF, page_fault); > > -#endif > > - load_idt(&idt_descr); > > This breaks 64-bit Xen PV guests: idt_setup_early_handler() is called > from x86_64_start_kernel(), which is not executed on those guests. early_trap_init() is called from setup_arch(), not from x86_64_start_kernel(). This patch merily renames the function and moves the code into a different source file. So it's not changing the behaviour in any way. > The patch below fixes it. I doubt that :) Thanks, tglx > diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c > index 03fb07d..ed0fb8a 100644 > --- a/arch/x86/xen/enlighten_pv.c > +++ b/arch/x86/xen/enlighten_pv.c > @@ -1374,6 +1374,7 @@ asmlinkage __visible void __init > xen_start_kernel(void) > i386_start_kernel(); > #else > cr4_init_shadow(); /* 32b kernel does this in i386_start_kernel() */ > + load_idt(&idt_descr); > x86_64_start_reservations((char *)__pa_symbol(&boot_params)); > #endif > }