From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from pandora.armlinux.org.uk (pandora.armlinux.org.uk [IPv6:2001:4d48:ad52:3201:214:fdff:fe10:1be6]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 40BsL35SdZzF1TR for ; Fri, 30 Mar 2018 04:33:47 +1100 (AEDT) Date: Thu, 29 Mar 2018 18:32:47 +0100 From: Russell King - ARM Linux To: Marc Zyngier Cc: Geert Uytterhoeven , Oliver , Rob Landley , Shea Levy , linux-riscv@lists.infradead.org, Linux Kernel Mailing List , Christoph Hellwig , Richard Henderson , Ivan Kokshaysky , Matt Turner , Vineet Gupta , Catalin Marinas , Will Deacon , Mark Salter , Aurelien Jacquiot , Mikael Starvik , Jesper Nilsson , Yoshinori Sato , Richard Kuo , Tony Luck , Fenghua Yu , James Hogan , Michal Simek , Ralf Baechle , David Howells , Ley Foon Tan , Jonas Bonn , Stefan Kristiansson , Stafford Horne , "James E.J. Bottomley" , Helge Deller , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Palmer Dabbelt , Albert Ou , Martin Schwidefsky , Heiko Carstens , Chen Liqin , Lennox Wu , Rich Felker , "David S. Miller" , Jeff Dike , Richard Weinberger , Guan Xuetao , Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , the arch/x86 maintainers , Chris Zankel , Max Filippov , Kate Stewart , Greg Kroah-Hartman , Philippe Ombredanne , Eugeniy Paltsev , Al Viro , Vladimir Murzin , Linus Walleij , Michal Hocko , Andrew Morton , Sudip Mukherjee , Rob Herring , Kees Cook , Vlastimil Babka , Balbir Singh , Christophe Leroy , Joe Perches , Dan Williams , Wei Yang , Christian =?iso-8859-1?Q?K=F6nig?= , Arnd Bergmann , Deepa Dinamani , Daniel Thompson , Florian Fainelli , alpha , arcml , Linux ARM , adi-buildroot-devel@lists.sourceforge.net, linux-c6x-dev@linux-c6x.org, Cris , "moderated list:H8/300 ARCHITECTURE" , "open list:QUALCOMM HEXAGON..." , linux-ia64@vger.kernel.org, linux-m68k , "open list:METAG ARCHITECTURE" , Linux MIPS Mailing List , "moderated list:PANASONIC MN10300..." , nios2-dev@lists.rocketboards.org, Openrisc , Parisc List , linuxppc-dev , linux-s390 , Linux-sh list , sparclinux , uml-devel , uml-user , linux-xtensa@linux-xtensa.org, Nicholas Piggin Subject: Re: [PATCH] Extract initrd free logic from arch-specific code. Message-ID: <20180329173247.GF16141@n2100.armlinux.org.uk> References: <20180328152714.6103-1-shea@shealevy.com> <05620fee-e8b5-0668-77b8-da073dc78c40@landley.net> <20180328164813.GA3888@n2100.armlinux.org.uk> <20180328221401.GA14084@n2100.armlinux.org.uk> <20180329152749.GC16141@n2100.armlinux.org.uk> <20180329155827.GD16141@n2100.armlinux.org.uk> <86zi2qrfgl.wl-marc.zyngier@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <86zi2qrfgl.wl-marc.zyngier@arm.com> Sender: Russell King - ARM Linux List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, Mar 29, 2018 at 05:53:14PM +0100, Marc Zyngier wrote: > On Thu, 29 Mar 2018 16:58:27 +0100, > Russell King - ARM Linux wrote: > > > > On Thu, Mar 29, 2018 at 05:43:47PM +0200, Geert Uytterhoeven wrote: > > > On Thu, Mar 29, 2018 at 5:27 PM, Russell King - ARM Linux > > > wrote: > > > > On Thu, Mar 29, 2018 at 09:37:52AM +1100, Oliver wrote: > > > >> On Thu, Mar 29, 2018 at 9:14 AM, Russell King - ARM Linux > > > >> wrote: > > > >> > On Wed, Mar 28, 2018 at 02:04:22PM -0500, Rob Landley wrote: > > > >> >> On 03/28/2018 11:48 AM, Russell King - ARM Linux wrote: > > > >> >> > On Wed, Mar 28, 2018 at 10:58:51AM -0500, Rob Landley wrote: > > > >> >> >> On 03/28/2018 10:26 AM, Shea Levy wrote: > > > >> >> >>> Now only those architectures that have custom initrd free requirements > > > >> >> >>> need to define free_initrd_mem. > > > >> >> >> ... > > > >> >> >>> --- a/arch/arc/mm/init.c > > > >> >> >>> +++ b/arch/arc/mm/init.c > > > >> >> >>> @@ -229,10 +229,3 @@ void __ref free_initmem(void) > > > >> >> >>> { > > > >> >> >>> free_initmem_default(-1); > > > >> >> >>> } > > > >> >> >>> - > > > >> >> >>> -#ifdef CONFIG_BLK_DEV_INITRD > > > >> >> >>> -void __init free_initrd_mem(unsigned long start, unsigned long end) > > > >> >> >>> -{ > > > >> >> >>> - free_reserved_area((void *)start, (void *)end, -1, "initrd"); > > > >> >> >>> -} > > > >> >> >>> -#endif > > > >> >> >>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > > > >> >> >>> index 3f972e83909b..19d1c5594e2d 100644 > > > >> >> >>> --- a/arch/arm/Kconfig > > > >> >> >>> +++ b/arch/arm/Kconfig > > > >> >> >>> @@ -47,6 +47,7 @@ config ARM > > > >> >> >>> select HARDIRQS_SW_RESEND > > > >> >> >>> select HAVE_ARCH_AUDITSYSCALL if (AEABI && !OABI_COMPAT) > > > >> >> >>> select HAVE_ARCH_BITREVERSE if (CPU_32v7M || CPU_32v7) && !CPU_32v6 > > > >> >> >>> + select HAVE_ARCH_FREE_INITRD_MEM > > > >> >> >>> select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU > > > >> >> >>> select HAVE_ARCH_KGDB if !CPU_ENDIAN_BE32 && MMU > > > >> >> >>> select HAVE_ARCH_MMAP_RND_BITS if MMU > > > >> >> >> > > > >> >> >> Isn't this why weak symbols were invented? > > > >> >> > > > > >> >> > Weak symbols means that we end up with both the weakly-referenced code > > > >> >> > and the arch code in the kernel image. That's fine if the weak code > > > >> >> > is small. > > > >> >> > > > >> >> The kernel's been able to build with link time garbage collection since 2016: > > > >> >> > > > >> >> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b67067f1176d > > > >> >> > > > >> >> Wouldn't that remove the unused one? > > > >> > > > > >> > Probably, if anyone bothered to use that, which they don't. > > > >> > > > > >> > LD_DEAD_CODE_DATA_ELIMINATION is a symbol without a prompt, and from > > > >> > what I can see, nothing selects it. Therefore, the symbol is always > > > >> > disabled, and so the feature never gets used in mainline kernels. > > > >> > > > > >> > Brings up the obvious question - why is it there if it's completely > > > >> > unused? (Maybe to cause confusion, and allowing a justification > > > >> > for __weak ?) > > > >> > > > >> IIRC Nick had some patches to do the arch enablement for powerpc, but > > > >> I'm not sure what happened to them though. I suspect it just fell down > > > >> Nick's ever growing TODO list. > > > > > > > > I've given it a go on ARM, marking every linker-built table with KEEP() > > > > and comparing the System.map files. The resulting kernel is around > > > > 150k smaller, which seems good. > > > > > > > > However, it doesn't boot - and I don't know why. Booting the kernel > > > > under kvmtool in a VM using virtio-console, I can find no way to get > > > > any kernel messages out of it. Using lkvm debug, I can see that the > > > > PC is stuck inside die(), and that's the only information I have. > > > > It dies before bringing up the other CPUs, so it's a very early death. > > > > > > > > I don't think other console types are available under ARM64. > > > > > > earlycon? > > > > Through what - as I say above, I think the only thing that's present is > > virtio-console, and the virtio stack only get initialised much later in > > boot. > > > > Eg, there's the memory-based virtio driver which interfaces any virtio > > driver to a memory-based ring structures for communication with the host > > (drivers/virtio/virtio_mmio.c) which is initialised at module_init() > > time, and so isn't available for earlycon. > > > > I don't think merely changing the module_init() calls in the appropriate > > virtio bits will suffice - it's why I pointed out that it dies before > > SMP initialisation, which also means that it dies before we start > > running the initcalls for subsystems and drivers. > > > > I'm not aware of there being an emulated UART in the guest's address > > space, so serial based stuff doesn't work. > > "earlycon=uart,mmio,0x3f8" is what you're looking for: Does that also mean that we have a RTC at the standard PC IO addresses as well, but in mmio space? -- RMK's Patch system: http://www.armlinux.org.uk/developer/patches/ FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up According to speedtest.net: 8.21Mbps down 510kbps up