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

Frans de Boer frans at fransdb.nl
Tue Jul 17 05:06:09 PDT 2018

On 07/14/2018 06:56 PM, Hazel Russman wrote:
> Gentlemen,
> 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
Hazel, sorry but where should I remove phys_to_virt()? If I delete the 
complete if statement in the iounmap function, and replace that with the 
above code, i get compile errors.

btw: acpi=off does not solve the issue too.


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