Boot issues with custom 64-bit kernel v3.19

[Greg KH]

On Mon, May 22, 2017 at 11:29:29AM -0400, Aditya Basu wrote:
> 
>     On Fri, May 05, 2017 at 04:58:27PM -0400, Aditya Basu wrote:
>     > I am trying to compile and boot Linux Kernel v3.19 (64-bit version) using
>     -
>     >
>     > make defconfig
>     > make kvmconfig
>     > make -j8
>     >
>     > The compilation works out without any errors but it doesn't boot
>     > inside qemu or my host machine.
>     > I use the following command line parameters to linux: "debug
>     > earlyprintk loglevel=7"
>     >
>     > # The boot hangs at the point -
>     > ####################################
>     > Booting from ROM...
>     > early console in setup code
>     > early console in decompress_kernel
>     >
>     > Decompressing Linux... Parking ELF... done.
>     > Booting the kernel .
>     > ####################################
>     >
>     > # Things I have tried so far:
>     > - Interestingly if I uncheck the 64-bit build in config (from make
>     > menuconfig), the resulting 32-bit kernel boots correctly.
>     >
>     > - Have tried running qemu with different cpus (host) + with & without
>     kvm.
>     >
>     > sudo qemu-system-x86_64 -m 4G -append 'debug earlyprintk loglevel=7'
>     > -kernel arch/x86/boot/bzImage -cpu host -enable-kvm
>     >
>     > I know the kernel will panic because of no root filesystem, but it
>     > happens later in the boot process. I am basing this from booting the
>     > 32 bit version of the kernel which prints out a lot of stuff and then
>     > panics due to no vfs_root.
>     >
>     > - The 64-bit versions of kernel v4.2 and above don't have this issue -
>     > meaning they boot correctly.
> 
>     Great!  Stick with newer kernels, 3.19 is really old, as is 4.2, lots
>     and lots of things have been fixed since then, you aren't going to be
>     able to get any help from anyone in the community if you use old kernels
>     like that, sorry.
> 
> 
> My primary goal is to build and boot LLVM Linux (http://
> llvm.linuxfoundation.org/index.php/Main_Page). This project has patches
> available only till kernel v3.19. That's why I am trying to use the older
> version 3.19.

4.11 should build/boot using llvm, or if not, I think 4.12-rc1 can, as
the remaining changes went in then.

No need to stick with an obsolete kernel version just to try out an
alternative compiler :)

good luck!

greg k-h