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Bug#834505: arm64 boot failure with large physical memory range



On Tue, Aug 16, 2016 at 04:39:15PM +0200, Hector Oron wrote:
> On Tue, Aug 16, 2016 at 01:13:28PM +0100, Leif Lindholm wrote:
> > Package: linux
> > Version: 4.6.4-1
> > X-Debbugs-CC: steve@einval.com, wookey@wookware.org, zheng.xu@linaro.org
> > 
> > Upstream commit 211102d85 ("arm64: defconfig: enable 48-bit virtual
> > addresses") changed the default configuration for arm64 to be 48-bit
> > VA (CONFIG_ARM64_VA_BITS_48). This is required in order to be able to
> > access the full amount of RAM available on some current arm64 systems
> > (currently with large memory holes, but could apply to any system with
> > >512GB of RAM). Without this, on these systems, the kernel will fail
> > to access the initrd, which will have been located near top of RAM by
> > GRUB. Error message given is:
> > ---
> > initrd not fully accessible via the linear mapping -- please check
> > your bootloader ...
> > ---
> > 
> > So please enable CONFIG_ARM64_VA_BITS_48 for arm64 kernels.
> > 
> > Note: this change _will_ cause breakage in certain userland software
> > making non-portable assumptions about available of top address bits
> > for pointer tagging - including luajit and mozilla-js (and hence
> > everything using mozilla-js).
> 
> FTR, this is an issue DSA is having booting arm64 machine donated by
> Gigabyte MR30-AR1. I am currently building a kernel, to get a d-i image
> and test this proposed fix.
> 
> I'll follow up with the results.

Ok, that worked fine, in addition to:
CONFIG_ARM64_VA_BITS_48=y
we also need to set on arm64
CONFIG_ACPI=y

As we are using ACPI for booting MR30-AR1 device.

Regards,
-- 
  Hector Oron

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