From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754426AbdJILiU (ORCPT ); Mon, 9 Oct 2017 07:38:20 -0400 Received: from terminus.zytor.com ([65.50.211.136]:38019 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751834AbdJILiS (ORCPT ); Mon, 9 Oct 2017 07:38:18 -0400 Date: Mon, 9 Oct 2017 04:36:01 -0700 From: tip-bot for Andy Lutomirski Message-ID: Cc: bp@alien8.de, tglx@linutronix.de, linux-kernel@vger.kernel.org, mingo@kernel.org, hpa@zytor.com, rostedt@goodmis.org, luto@kernel.org Reply-To: luto@kernel.org, rostedt@goodmis.org, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@kernel.org, tglx@linutronix.de, bp@alien8.de In-Reply-To: References: To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/mm/64: Fix reboot interaction with CR4.PCIDE Git-Commit-ID: 924c6b900cfdf376b07bccfd80e62b21914f8a5a X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 924c6b900cfdf376b07bccfd80e62b21914f8a5a Gitweb: https://git.kernel.org/tip/924c6b900cfdf376b07bccfd80e62b21914f8a5a Author: Andy Lutomirski AuthorDate: Sun, 8 Oct 2017 21:53:05 -0700 Committer: Thomas Gleixner CommitDate: Mon, 9 Oct 2017 13:31:04 +0200 x86/mm/64: Fix reboot interaction with CR4.PCIDE Trying to reboot via real mode fails with PCID on: long mode cannot be exited while CR4.PCIDE is set. (No, I have no idea why, but the SDM and actual CPUs are in agreement here.) The result is a GPF and a hang instead of a reboot. I didn't catch this in testing because neither my computer nor my VM reboots this way. I can trigger it with reboot=bios, though. Fixes: 660da7c9228f ("x86/mm: Enable CR4.PCIDE on supported systems") Reported-and-tested-by: Steven Rostedt (VMware) Signed-off-by: Andy Lutomirski Signed-off-by: Thomas Gleixner Cc: Borislav Petkov Link: https://lkml.kernel.org/r/f1e7d965998018450a7a70c2823873686a8b21c0.1507524746.git.luto@kernel.org --- arch/x86/kernel/reboot.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index 54180fa..add33f6 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -105,6 +105,10 @@ void __noreturn machine_real_restart(unsigned int type) load_cr3(initial_page_table); #else write_cr3(real_mode_header->trampoline_pgd); + + /* Exiting long mode will fail if CR4.PCIDE is set. */ + if (static_cpu_has(X86_FEATURE_PCID)) + cr4_clear_bits(X86_CR4_PCIDE); #endif /* Jump to the identity-mapped low memory code */