From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id E54AE280300 for ; Wed, 2 Aug 2017 03:44:58 -0400 (EDT) Received: by mail-wr0-f197.google.com with SMTP id u89so5044356wrc.1 for ; Wed, 02 Aug 2017 00:44:58 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id d36si27280720wrd.455.2017.08.02.00.44.57 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 02 Aug 2017 00:44:57 -0700 (PDT) Subject: Re: [PATCHv2 08/10] x86/mm: Replace compile-time checks for 5-level with runtime-time References: <20170718141517.52202-1-kirill.shutemov@linux.intel.com> <20170718141517.52202-9-kirill.shutemov@linux.intel.com> <6841c4f3-6794-f0ac-9af9-0ceb56e49653@suse.com> <20170725090538.26sbgb4npkztsqj3@black.fi.intel.com> <39cb1e36-f94e-32ea-c94a-2daddcbf3408@suse.com> <20170726164335.xaajz5ltzhncju26@node.shutemov.name> <20170801144414.rd67k2g2cz46nlow@black.fi.intel.com> <20170801191144.k333twdie52arpwt@black.fi.intel.com> From: Juergen Gross Message-ID: <2c425437-f887-8a7e-9bce-36338c0979d0@suse.com> Date: Wed, 2 Aug 2017 09:44:54 +0200 MIME-Version: 1.0 In-Reply-To: <20170801191144.k333twdie52arpwt@black.fi.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: "Kirill A. Shutemov" , Linus Torvalds , Andrew Morton , x86@kernel.org, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Andi Kleen , Dave Hansen , Andy Lutomirski , Michal Hocko , linux-mm@kvack.org, linux-kernel@vger.kernel.org On 01/08/17 21:11, Kirill A. Shutemov wrote: > On Tue, Aug 01, 2017 at 07:14:57PM +0200, Juergen Gross wrote: >> On 01/08/17 16:44, Kirill A. Shutemov wrote: >>> On Tue, Aug 01, 2017 at 09:46:56AM +0200, Juergen Gross wrote: >>>> On 26/07/17 18:43, Kirill A. Shutemov wrote: >>>>> On Wed, Jul 26, 2017 at 09:28:16AM +0200, Juergen Gross wrote: >>>>>> On 25/07/17 11:05, Kirill A. Shutemov wrote: >>>>>>> On Tue, Jul 18, 2017 at 04:24:06PM +0200, Juergen Gross wrote: >>>>>>>> Xen PV guests will never run with 5-level-paging enabled. So I guess you >>>>>>>> can drop the complete if (IS_ENABLED(CONFIG_X86_5LEVEL)) {} block. >>>>>>> >>>>>>> There is more code to drop from mmu_pv.c. >>>>>>> >>>>>>> But while there, I thought if with boot-time 5-level paging switching we >>>>>>> can allow kernel to compile with XEN_PV and XEN_PVH, so the kernel image >>>>>>> can be used in these XEN modes with 4-level paging. >>>>>>> >>>>>>> Could you check if with the patch below we can boot in XEN_PV and XEN_PVH >>>>>>> modes? >>>>>> >>>>>> We can't. I have used your branch: >>>>>> >>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/kas/linux.git >>>>>> la57/boot-switching/v2 >>>>>> >>>>>> with this patch applied on top. >>>>>> >>>>>> Doesn't boot PV guest with X86_5LEVEL configured (very early crash). >>>>> >>>>> Hm. Okay. >>>>> >>>>> Have you tried PVH? >>>>> >>>>>> Doesn't build with X86_5LEVEL not configured: >>>>>> >>>>>> AS arch/x86/kernel/head_64.o >>>>> >>>>> I've fixed the patch and split the patch into two parts: cleanup and >>>>> re-enabling XEN_PV and XEN_PVH for X86_5LEVEL. >>>>> >>>>> There's chance that I screw somthing up in clenaup part. Could you check >>>>> that? >>>> >>>> Build is working with and without X86_5LEVEL configured. >>>> >>>> PV domU boots without X86_5LEVEL configured. >>>> >>>> PV domU crashes with X86_5LEVEL configured: >>>> >>>> xen_start_kernel() >>>> x86_64_start_reservations() >>>> start_kernel() >>>> setup_arch() >>>> early_ioremap_init() >>>> early_ioremap_pmd() >>>> >>>> In early_ioremap_pmd() there seems to be a call to p4d_val() which is an >>>> uninitialized paravirt operation in the Xen pv case. >>> >>> Thanks for testing. >>> >>> Could you check if patch below makes a difference? >> >> A little bit better. I get a panic message with backtrace now: > > Are you running with 512m of ram or so? Yes. :-) > There's known issue with sparse mem: it still allocate data structures as > if there's 52-bit phys address space even for p4d_folded case. > > I'm looking this. > > Try to bump memory size to 2g or so for now. That did the trick! PV domU is coming up now with a 5-level paging enabled kernel. Juergen -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org