From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EB8FAC47257 for ; Tue, 5 May 2020 14:17:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D6918207DD for ; Tue, 5 May 2020 14:17:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730222AbgEEORE (ORCPT ); Tue, 5 May 2020 10:17:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1730207AbgEEOQ6 (ORCPT ); Tue, 5 May 2020 10:16:58 -0400 Received: from Galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62F71C0610D6 for ; Tue, 5 May 2020 07:16:58 -0700 (PDT) Received: from p5de0bf0b.dip0.t-ipconnect.de ([93.224.191.11] helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1jVyN7-0002N6-F3; Tue, 05 May 2020 16:16:33 +0200 Received: from nanos.tec.linutronix.de (localhost [IPv6:::1]) by nanos.tec.linutronix.de (Postfix) with ESMTP id E6C69FFC8D; Tue, 5 May 2020 16:16:32 +0200 (CEST) Message-Id: <20200505135829.108410360@linutronix.de> User-Agent: quilt/0.65 Date: Tue, 05 May 2020 15:53:51 +0200 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, "Paul E. McKenney" , Andy Lutomirski , Alexandre Chartre , Frederic Weisbecker , Paolo Bonzini , Sean Christopherson , Masami Hiramatsu , Petr Mladek , Steven Rostedt , Joel Fernandes , Boris Ostrovsky , Juergen Gross , Brian Gerst , Mathieu Desnoyers , Josh Poimboeuf , Will Deacon Subject: [patch V4 part 5 10/31] x86/entry: Change exit path of xen_failsafe_callback References: <20200505135341.730586321@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org xen_failsafe_callback is invoked from XEN for two cases: 1. Fault while reloading DS, ES, FS or GS 2. Fault while executing IRET #1 retries the IRET after XEN has fixed up the segments. #2 injects a #GP which kills the task For #1 there is no reason to go through the full exception return path because the tasks TIF state is still the same. So just going straight to the IRET path is good enough. Signed-off-by: Thomas Gleixner Cc: Boris Ostrovsky Cc: Juergen Gross --- arch/x86/entry/entry_32.S | 2 +- arch/x86/entry/entry_64.S | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1352,7 +1352,7 @@ SYM_FUNC_START(xen_failsafe_callback) 5: pushl $-1 /* orig_ax = -1 => not a system call */ SAVE_ALL ENCODE_FRAME_POINTER - jmp ret_from_exception + jmp handle_exception_return .section .fixup, "ax" 6: xorl %eax, %eax --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1137,7 +1137,7 @@ SYM_CODE_START(xen_failsafe_callback) pushq $-1 /* orig_ax = -1 => not a system call */ PUSH_AND_CLEAR_REGS ENCODE_FRAME_POINTER - jmp error_exit + jmp error_return SYM_CODE_END(xen_failsafe_callback) #endif /* CONFIG_XEN_PV */