From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751440AbeECOpy (ORCPT ); Thu, 3 May 2018 10:45:54 -0400 Received: from smtp.ctxuk.citrix.com ([185.25.65.24]:63202 "EHLO SMTP.EU.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751050AbeECOpw (ORCPT ); Thu, 3 May 2018 10:45:52 -0400 X-IronPort-AV: E=Sophos;i="5.49,358,1520899200"; d="scan'208";a="72566471" From: Roger Pau Monne To: CC: Roger Pau Monne , Boris Ostrovsky , Juergen Gross , Subject: [PATCH 1/3] xen/pvh: enable and set default MTRR type Date: Thu, 3 May 2018 15:44:59 +0100 Message-ID: <20180503144459.61007-1-roger.pau@citrix.com> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180503143646.60747-1-roger.pau@citrix.com> References: <20180503143646.60747-1-roger.pau@citrix.com> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On PVH MTRR is not initialized by the firmware (because there's no firmware), so the kernel is started with MTRR disabled which means all memory accesses are UC. So far there have been no issues (ie: slowdowns) caused by this because PVH only supported DomU mode without passed-through devices, so Xen was using WB as the default memory type instead of UC. Fix this by enabling MTRR and setting the default type to WB. Linux will use PAT to set the actual memory cache attributes. Signed-off-by: Boris Ostrovsky Signed-off-by: Roger Pau Monné --- Cc: Boris Ostrovsky Cc: Juergen Gross Cc: xen-devel@lists.xenproject.org --- arch/x86/xen/enlighten_pvh.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c index aa1c6a6831a9..e039d1809809 100644 --- a/arch/x86/xen/enlighten_pvh.c +++ b/arch/x86/xen/enlighten_pvh.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include @@ -98,6 +99,8 @@ void __init xen_prepare_pvh(void) xen_pvh = 1; + wrmsr_safe(MSR_MTRRdefType, 0x800 | MTRR_TYPE_WRBACK, 0); + msr = cpuid_ebx(xen_cpuid_base() + 2); pfn = __pa(hypercall_page); wrmsr_safe(msr, (u32)pfn, (u32)(pfn >> 32)); -- 2.17.0