Hi.

We've recompiled a 2.4.20-19.8smp kernel with a larger VMALLOC value in page.h:
#define ___VMALLOC_RESERVE (256 << 20)

This makes the kernel panic with "VFS: Unable to mount root FS on 00:00".

mem=640m boots fine, anything above crashes. Lilo has no problem with it.

Any ideas? Cheers.

Not sure, but I know grub insists on loading to a certain portion of ram,i.e. a specific memory address. If something else is trying to use it it won't work, i.e. another hardware device might also insist on that memory address. You may have reserved that sector of ram that grub and something else both need. Lilo is not as picky.

I am almost afraid to ask.

What is the best workaround here?

Should I reserver a different vmalloc address space? Or is there another option to grub that would allow it to load alsewhere in RAM space?

Thanks.

My speculation is based on the well documented problems that grub has with the nforce chipsets with onboard grapics adapter. The grapics adapter insisted on grabbing the low memory addresses that grub needed resulting in a memory allocation error or out of mem condition when you attempted to boot. Apparently grub needs those low memory addresses. The posted solution was always to use lilo.
What sparked my interest is that for you lilo was working and grub would not. You appear fairly knowledgable so I assumed lilo and grub were both properly configured. I thought something may be overwriting the low mem addresses when you do not set mem=640m; it may also be a memory mapping problem peculiar to grub.
I don't really know enough about it to give you any meaningful help beyond the above. However, if lilo is working, I'd just stick with it.

But the kernel panics way before any graphics driver modules get loaded.

Would you be so kind as sending me the link to the thread you were referring to?

You are also right about looking to another forum for my problem, since we are recompiling a kernel with some custom values for vmalloc.

Regards

It isn't the graphics driver; it occurs at the bios level. The bios reserves a portion of ram for the onboard graphics that grub needs. If you google "grub nforce ram" you should find some links on this problem. One thing I noticed digging around on google is the problem was mainly with grub 0.92. The problem was also reported in the gentoo install documents but now has been removed. Some of the newsgroup posts seem to indicate that upgrading to grub 0.93 solved the problem. Since it's been removed from the gentoo forum I suspect that 0.93 may have corrected this problem. If your using 0.92, you might want to try upgrading to 0.93.