From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754603AbdHZK7I (ORCPT ); Sat, 26 Aug 2017 06:59:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:49272 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754548AbdHZK7H (ORCPT ); Sat, 26 Aug 2017 06:59:07 -0400 Subject: Re: [patch V2 35/44] x86/idt: Switch early trap init to IDT tables To: Thomas Gleixner , Boris Ostrovsky Cc: LKML , Ingo Molnar , Peter Anvin , Peter Zijlstra , Andy Lutomirski , Borislav Petkov , Steven Rostedt References: <20170825214648.264521964@linutronix.de> <20170825214942.983480384@linutronix.de> <7e182f46-d27b-9414-fb6d-ee48906a4180@oracle.com> From: Juergen Gross Message-ID: Date: Sat, 26 Aug 2017 12:59:03 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26/08/17 10:16, Thomas Gleixner wrote: > 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. It does: the IDT entries are now statically defined. Before that any call of set_intr_gate() would have registered the trap handler with the hypervisor, now this is done only when the IDT is being activated. Boris' patch is doing that. > >> The patch below fixes it. > > I doubt that :) Me not. :-) Juergen > > 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 >> } > >