Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751129AbaLPJ6q (ORCPT ); Tue, 16 Dec 2014 04:58:46 -0500 Received: from cantor2.suse.de ([195.135.220.15]:46668 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750935AbaLPJ6n (ORCPT ); Tue, 16 Dec 2014 04:58:43 -0500 From: Juergen Gross To: hpa@zytor.com, x86@kernel.org, tglx@linutronix.de, mingo@redhat.com, linux-kernel@vger.kernel.org, akataria@vmware.com, jongman.heo@samsung.com Cc: Juergen Gross Subject: [PATCH] x86: don't rely on VMWare emulating PAT MSR correctly Date: Tue, 16 Dec 2014 10:58:34 +0100 Message-Id: <1418723914-9736-1-git-send-email-jgross@suse.com> X-Mailer: git-send-email 2.1.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org VMWare seems not to emulate the PAT MSR correctly: reaeding MSR_IA32_CR_PAT returns 0 even after writing another value to it. Detect this bug and don't use the read value if it is 0. Commit bd809af16e3ab1f8d55b3e2928c47c67e2a865d2 ("x86: Enable PAT to use cache mode translation tables") triggers this VMWare bug when the kernel is booted as a VMWare guest. Reported-by: Jongman Heo Signed-off-by: Juergen Gross Tested-by: Jongman Heo --- arch/x86/mm/pat.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index edf299c..7ac6869 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -234,8 +234,13 @@ void pat_init(void) PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); /* Boot CPU check */ - if (!boot_pat_state) + if (!boot_pat_state) { rdmsrl(MSR_IA32_CR_PAT, boot_pat_state); + if (!boot_pat_state) { + pat_disable("PAT read returns always zero, disabled."); + return; + } + } wrmsrl(MSR_IA32_CR_PAT, pat); -- 2.1.2 -- 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/