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ipic
Guru
Joined: 29 Dec 2003
Posts: 412
Location: UK
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 Posted: Wed Jan 08, 2025 10:16 am Post subject: [SOLVED ]qemu - 32 bit vm boot fails from version 8.2.7 |
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Upgraded qemu from 8.2.3 to 8.2.7 (i'm following stable versions in portage).
After this - my 32-bit VM's failed to boot, reason being that the boot drive could not be opened (invalid file system). 64bit VM's boot OK, so this is a 32 bit kernel problem.
After some digging, the blame 'appears' to be with the seabios release that also got updated (sys-firmware/seabios-bin 1.16.0 -> 1.16.3)
I found this post: https://mail.coreboot.org/hyperkitty/list/seabios@seabios.org/message/E6W2C4GZCEQ4KZ3WJUN5HRH54GBRWSQT/
It is an old article, but suggests:
| Code: |
Recommended action: turn off 64-bit support (long mode) in the cpu:
qemu -cpu host,lm=off |
I'd like to try this, but I cannot find a way to set that in libvirt XML.
Anyone know how?
Last edited by ipic on Wed Jan 08, 2025 2:00 pm; edited 1 time in total |
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ipic
Guru
Joined: 29 Dec 2003
Posts: 412
Location: UK
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| Posted: Wed Jan 08, 2025 1:23 pm Post subject: |
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I forced a downgrade of seabios with qemu 8.2.7 installed, and the 32-bit VMs boot with seabios 1.16.0.
So, seabios is definitely the culprit.
I can't figure out what to change to make it work though  |
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grknight
Retired Dev
Joined: 20 Feb 2015
Posts: 1975
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| Posted: Wed Jan 08, 2025 1:36 pm Post subject: |
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To disable 64-bit host detection for libvirt, in the CPU definition, add: | Code: | | <feature policy='disable' name='lm'/> |
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ipic
Guru
Joined: 29 Dec 2003
Posts: 412
Location: UK
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| Posted: Wed Jan 08, 2025 1:57 pm Post subject: |
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| grknight wrote: | To disable 64-bit host detection for libvirt, in the CPU definition, add: | Code: | | <feature policy='disable' name='lm'/> |
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Thank you sir!
I did the upgrade, added that line to the VM XML, and now the 32bit VM's boot.
Just for full reference the XML snippet that libvirt creates is:
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<cpu mode="host-model" check="partial">
<feature policy="disable" name="lm"/>
</cpu>
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Thanks again. |
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