From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH 11/12] kexec: allow architectures to override boot mapping Date: Fri, 29 Apr 2016 19:08:28 +0100 Message-ID: <20160429180828.GU19428@n2100.arm.linux.org.uk> References: <20160428092644.GX19428@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-doc-owner@vger.kernel.org To: Pratyush Anand Cc: linux-arm-kernel@lists.infradead.org, Mark Rutland , devicetree@vger.kernel.org, Tony Luck , linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org, Pawel Moll , Jonathan Corbet , Ian Campbell , kexec@lists.infradead.org, Fenghua Yu , Haren Myneni , Rob Herring , Eric Biederman , Santosh Shilimkar , Kumar Gala , Vivek Goyal List-Id: devicetree@vger.kernel.org On Fri, Apr 29, 2016 at 08:44:29PM +0530, Pratyush Anand wrote: > On Thu, Apr 28, 2016 at 2:58 PM, Russell King > wrote: > > kexec physical addresses are the boot-time view of the system. For > > certain ARM systems (such as Keystone 2), the boot view of the system > > does not match the kernel's view of the system: the boot view uses a > > special alias in the lower 4GB of the physical address space. > > > > To cater for these kinds of setups, we need to translate between the > > boot view physical addresses and the normal kernel view physical > > addresses. This patch extracts the current transation points into > > linux/kexec.h, and allows an architecture to override the functions. > > > > Due to the translations required, we unfortunately end up with six > > translation functions, which are reduced down to four that the > > architecture can override. > > > > Signed-off-by: Russell King > > I must be missing something when I am thinking that, had we passed > arch_phys_to_idmap_offset to user space, this patch would not have > been needed, and things would have been more simpler. Please help me > to understand why passing arch_phys_to_idmap_offset to user space > would not be a good idea. Sorry, I disagree. Even if we thought that passing the offset to userspace would be a good idea, it does nothing to solve each site in this patch. This patch would still be necessary. -- RMK's Patch system: http://www.arm.linux.org.uk/developer/patches/ FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up according to speedtest.net.