From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f198.google.com (mail-wr0-f198.google.com [209.85.128.198]) by kanga.kvack.org (Postfix) with ESMTP id 9F3086B0033 for ; Wed, 29 Nov 2017 11:40:45 -0500 (EST) Received: by mail-wr0-f198.google.com with SMTP id o20so2242112wro.8 for ; Wed, 29 Nov 2017 08:40:45 -0800 (PST) Received: from Galois.linutronix.de (Galois.linutronix.de. [2a01:7a0:2:106d:700::1]) by mx.google.com with ESMTPS id q127si1674357wmb.20.2017.11.29.08.40.43 for (version=TLS1_2 cipher=AES128-SHA bits=128/128); Wed, 29 Nov 2017 08:40:44 -0800 (PST) Date: Wed, 29 Nov 2017 17:40:32 +0100 (CET) From: Thomas Gleixner Subject: Re: [PATCHv2 0/4] x86: 5-level related changes into decompression code In-Reply-To: <20171129161349.d7ksuhwhdamloty6@node.shutemov.name> Message-ID: References: <20171110220645.59944-1-kirill.shutemov@linux.intel.com> <20171129154908.6y4st6xc7hbsey2v@pd.tnic> <20171129161349.d7ksuhwhdamloty6@node.shutemov.name> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: "Kirill A. Shutemov" Cc: Borislav Petkov , "Kirill A. Shutemov" , Ingo Molnar , x86@kernel.org, "H. Peter Anvin" , Linus Torvalds , Andy Lutomirski , Cyrill Gorcunov , Andi Kleen , linux-mm@kvack.org, linux-kernel@vger.kernel.org On Wed, 29 Nov 2017, Kirill A. Shutemov wrote: > On Wed, Nov 29, 2017 at 04:49:08PM +0100, Borislav Petkov wrote: > > On Sat, Nov 11, 2017 at 01:06:41AM +0300, Kirill A. Shutemov wrote: > > > Hi Ingo, > > > > > > Here's updated changes that prepare the code to boot-time switching between > > > paging modes and handle booting in 5-level mode when bootloader put kernel > > > image above 4G, but haven't enabled 5-level paging for us. > > > > Btw, if I enable CONFIG_X86_5LEVEL with 4.15-rc1 on an AMD box, the box > > triple-faults and ends up spinning in a reboot loop. Even though it > > should say: > > > > early console in setup code > > This kernel requires the following features not present on the CPU: > > la57 > > Unable to boot - please use a kernel appropriate for your CPU. > > > > and halt. > > > > A kvm guest still does that but baremetal triple-faults. > > > > Ideas? > > Looks like we call check_cpuflags() too late. 5-level paging gets enabled > before image decompression started. > > For qemu/kvm it works because it's supported in softmmu, even if not > advertised in cpuid. > > I'm not sure if it worth fixing on its own. I would rather get boot-time > switching code upstream sooner. It will get problem go away naturally. It needs to be fixed now. Because that problem exists in 4.14 Thanks, tglx -- 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