[lfs-support] Kernel bug involving physical to virtual remapping

Hazel Russman hazeldebian at googlemail.com
Sat Jul 14 09:56:43 PDT 2018


I was given your contact details by Michael Shell, who has been helping me to troubleshoot this problem via the Linux From Scratch support list.

For some time now I have been unable to boot recent kernels (4.14 or later) on my rather elderly desktop machine. The kernel panics during boot and the problem seems (superficially) to lie in the acpi driver. At least that is where the visible error messages come from. Booting with "acpi=off" works but is hardly an ideal solution.

However a git bisection showed that this is actually a memory management issue. The kernel commit that caused the problem is :
[33c2b803edd13487518a2c7d5002d84d7e9c878f] x86/mm: Remove
phys_to_virt() usage in ioremap().

Reintroducing the code:
"if (is_ISA_range(phys_addr, last_addr))
	return (__force void __iomem *)phys_to_virt(phys_addr);" 
makes the system bootable again. I have also tested this on a 4.15 kernel and it works there too.

If you want me to carry out any further tests, I would be happy to oblige, but do please bear in mind that I am not an expert, so you will need to give fairly basic instructions.

Hazel Russman 


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