Comment 214 for bug 930447

On 2013-11-24 11:13, roland aus köln wrote:
> i did a comparison of the installer`s kernel .config with the kernel
> .config of my working system - and they appear nearly identical:
>
> 3c3
> < # Linux/i386 3.11.0-12-generic Kernel Configuration
> ---
>> # Linux/i386 3.11.0-13-generic Kernel Configuration
> 68c68
> < CONFIG_VERSION_SIGNATURE="Ubuntu 3.11.0-12.19-generic 3.11.3"
> ---
>> CONFIG_VERSION_SIGNATURE="Ubuntu 3.11.0-13.20-generic 3.11.6"
> 5435c5435
> < CONFIG_USB_OTG=y
> ---
>> # CONFIG_USB_OTG is not set
> 5703d5702
> < CONFIG_USB_ZERO_HNPTEST=y
> 6717a6717
>> CONFIG_DM_RAID45=m
>
> so i would confirm the suspicion that the problem must be related to the
> bootloader somehow.
>
> but the question is if syslinux makes the kernel fail boot or if grub
> has something "inside" which avoids the kernel fail to boot.
>
> if PAE cpu flag is not available in some processor`s CPUID, i wonder why
> the kernel can boot. does linux kernel not check for cpu flags and does
> it detect pae capability differently (i.e. more reliable?)
>
The flag is only an indicator, that is used by other programs to decide
what to do. Most Celeron M and Pentium M computers have PAE capability,
at least they can manage to run PAE kernels without problems. But there
is no PAE flag.

There are at least two checks,

- in syslinux that prevents installation if there is no PAE flag

- in the system for upgrading, that prevents upgrading to a new kernel.
I guess more precisely it prevents upgrading to a PAE kernel, if there
is no PAE flag.

But there is no check in grub, so that way we can boot the kernel.

-o-

If you have the time and insight to fix these issues, we are many people
who would be happy :-)

Best regards
Nio