From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1g54ew-0001nm-Ag for kexec@lists.infradead.org; Wed, 26 Sep 2018 07:54:59 +0000 Date: Wed, 26 Sep 2018 15:54:33 +0800 From: Baoquan He Subject: Re: [PATCH 1/3] x86/boot: Add bit fields into xloadflags for 5-level kernel checking Message-ID: <20180926075433.GD2555@MiWiFi-R3L-srv> References: <20180829141624.13985-1-bhe@redhat.com> <20180829141624.13985-2-bhe@redhat.com> <6ea94875-ae07-6220-eb3e-d3f830cdac03@zytor.com> <20180904034414.GI1740@192.168.1.3> <4546fc39-4982-4c91-c812-0df1e9bc9e20@zytor.com> <20180904052036.GJ1740@192.168.1.3> <20180904084231.ubyjaqp4xhqcnper@kshutemo-mobl1> <7a1147d7-05af-98fe-3a14-b18ea445c2b5@zytor.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Thomas Gleixner , mingo@kernel.org, "H. Peter Anvin" Cc: "Kirill A. Shutemov" , x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kirill.shutemov@linux.intel.com On 09/05/18 at 10:02am, Thomas Gleixner wrote: > On Tue, 4 Sep 2018, H. Peter Anvin wrote: > > > On 09/04/18 01:42, Kirill A. Shutemov wrote: > > > > > > Switching between 4- and 5-level paging modes (in either direction) > > > requires paing disabling. It means the code that does the switching has to > > > be under 4G otherwise we would lose control. > > > > > > We handle the switching correctly in kernel decompression code, but not on > > > kexec caller side. > > > > > > XLF_5LEVEL indicates that kernel decompression code can deal with > > > switching between paging modes and it's safe to jump there in 5-level > > > paging mode. > > > > > > As an alternative we can change kexec to switch to 4-level paging mode > > > before starting the new kernel. Not sure how hard it will be. > > > > > > > Have a flag saying entering in 5-level mode is fine. However, you really > > should support returning to 4-level mode in kexec. It is *much* easier to do > > on the caller side as you have total control of memory allocation there. > > Works for a regular kexec, but not for starting a crash kernel.... Agree, it's not appropriate to do this after normal kernel crashed and prepare to jump to 2nd kernel. Can this patchset be merged? I will post patches to kexec-tools utility since it will make use of these flags. Thanks Baoquan _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec