linux-kernel - Re: Trying to kexec on Allwinner A80

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Date:   Tue, 7 Apr 2020 08:31:17 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Corentin Labbe <clabbe.montjoie@...il.com>
Cc:     ebiederm@...ssion.com, kexec@...ts.infradead.org, wens@...e.org,
        linux-arm-kernel@...ts.infradead.org, mripard@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: Trying to kexec on Allwinner A80

On Mon, Apr 06, 2020 at 10:10:53PM +0200, Corentin Labbe wrote:
> On Mon, Apr 06, 2020 at 10:37:29AM +0100, Russell King - ARM Linux admin wrote:
> > On Mon, Apr 06, 2020 at 11:25:40AM +0200, Corentin Labbe wrote:
> > > On Mon, Apr 06, 2020 at 10:16:00AM +0100, Russell King - ARM Linux admin wrote:
> > > > On Mon, Apr 06, 2020 at 10:27:20AM +0200, Corentin Labbe wrote:
> > > > > Hello
> > > > > 
> > > > > I am trying to add the last missing Allwinner Soc in kernelci: the A80.
> > > > > But this SoC does not have any way to be used in kernelci, no USB nor network in uboot.
> > > > > So I have tried to fake uboot since the kernel has network support and run the new kernel via kexec.
> > > > > 
> > > > > But kexec 2.0.18 fail to work:
> > > > > kexec --force /tmp/kernel --initrd /tmp/ramdisk --dtb /tmp/dtb --command-line='console=ttyS0,115200n8 root=/dev/ram0 earlycon=uart,mmio32,0x7000000 ip=dhcp'
> > > > 
> > > > What happens if you omit the dtb argument?
> > > > 
> > > 
> > > No change without dtb
> > > 
> > > I have also tried to add --mem-mim and --mem-max without any change.
> > > I given mem according to what I saw in /proc/iomem
> > > 20000000-9fffffff : System RAM
> > >   20008000-207fffff : Kernel code
> > >   20900000-209a0c87 : Kernel data
> > > So I gave --mem-min 0x30000000 --mem-max 0x9fffffff
> > > Anyway, the result is always the same.
> > 
> > The next step is to enable the early debugging - first in the
> > decompressor - add #define DEBUG to the top of
> > arch/arm/boot/compressed/head.S
> > 
> > Also enable DEBUG_LL in the kernel and use earlyprintk to see if you can
> > get anything from the new kernel.
> > 
> 
> I dont know what happened, but now I always get "Could not find a free area of memory of 0x86c1c0 bytes..." (even with kexec 2.0.18)
> Furthermore, I have added crashkernel=128M to the cmdlist
> I have verified that the reservation is working:
> 20000000-9fffffff : System RAM
>   20008000-207fffff : Kernel code
>   20900000-209a0c87 : Kernel data
>   40000000-47ffffff : Crash kernel
> But even with this reservation, no change.

crashkernel is only necessary if you're loading a kenrel image to be
booted when the existing one has crashed. For the problem you're
seeing, it's an unnecessary additional change; please drop that.

You could try running kexec with debug enabled to see more information.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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