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

Frans de Boer frans at fransdb.nl
Thu Jul 19 06:32:46 PDT 2018


On 19-07-18 14:57, Hazel Russman wrote:
> On Thu, 19 Jul 2018 13:54:19 +0200
> Frans de Boer <frans at fransdb.nl> wrote:
>>>>> 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.
>>>>>
>>
>> Hello Hazel,
>>
>> What you inserted is already available as from the 4.13.0 release. But I
>> can't compile 4.13. anymore because I now have gcc 8.1 instead of the
>> former 7 series.
>>
>> I continue my search and go for 4.14 where the check is removed. But i
>> guess that will fail too and this is no solution to my problem with
>> systemd freezing just after it found out that it is on a VM.
>>
>> --- Frans
>>
>> -- 
> Yes, I can boot 4.13 kernels without any problems. But I wanted an LTS kernel that can keep up with the newest exploits (especially meltdown) and the next LTS after 4.9 is 4.14. I'm using bare iron, not a VM (and no systemd!), but it's rather old hardware. The processor is an Intel Core Duo. I can send you the cpuinfo if you want it.
> 
> I suspect that if you did build 4.14, it would behave properly; after all, it does for most people. I have 4.15 on my laptop (which has a Via Nano processor) and no problems there. But I'd be happy to carry out any exploratory tests you like on my desktop, since that's the machine that misbehaves.
> 
Hello Hazel,

I get the impression you have been send to me with the wrong 
info/background. I have no problem running things on bare metal, but it 
is the problem with LFS and having systemd on a VM. As explained in the 
thread 'Booting LFS with Systemd'.
I know that Bruce uses bare metal too, but why not using VM's when one 
can continue developing without having to reboot into an incomplete 
system environment. Also, if one has multiple systems to spare, bare 
metal can be a way. If not, VM's are a welcome solution.

So, I think that I am chasing the wrong ghost and have a talk with the 
systemd developers instead. Despite the lack of interest for using VM's, 
I shall share any positive result with the LFS list.

Discussing closed.

Regards Frans.



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