[pve-devel] [PATCH qemu-server] Properly identify the CPU architecture of 32-bit VMs

[Filip Schauer]

On 12/12/2023 12:48, Fiona Ebner wrote:
> Am 12.12.23 um 11:39 schrieb Filip Schauer:
>> It's actually not a different binary. qemu-system-i386 is a symlink that
>> points to qemu-system-x86_64. But still this does indeed break migration
>> between a node that has this patch applied and another node without the
>> patch.
>>
> Oh, okay. But then that's a bit surprising. From a quick glance, we do
> have some logic matching arch 'x86_64' specifically in CPUConfig.pm, so
> that might be it. E.g.:
>
>>      my $pve_forced_flags = {};
>>      $pve_forced_flags->{'enforce'} = {
>>          reason => "error if requested CPU settings not available",
>>      } if $cputype ne 'host' && $kvm && $arch eq 'x86_64';


This check does not make any difference in my case since $kvm is not set
when using a qemu32 CPU.

Not sure what causes this to break migration, not that it matters but
here are my results anyway.

Journal of an unpatched node when migrating a running VM with CPU type
qemu32 from a node with this patch v1 applied:

Dec 13 18:09:28 pve2 QEMU[124616]: KVM: entry failed, hardware error 
0x80000021
Dec 13 18:09:28 pve2 QEMU[124616]: If you're running a guest on an Intel 
machine without unrestricted mode
Dec 13 18:09:28 pve2 QEMU[124616]: support, the failure can be most 
likely due to the guest entering an invalid
Dec 13 18:09:28 pve2 QEMU[124616]: state for Intel VT. For example, the 
guest maybe running in big real mode
Dec 13 18:09:28 pve2 QEMU[124616]: which is not supported on less recent 
Intel processors.
Dec 13 18:09:28 pve2 QEMU[124616]: EAX=00003433 EBX=0006880c 
ECX=00002fa5 EDX=89817860
Dec 13 18:09:28 pve2 QEMU[124616]: ESI=898098c0 EDI=8980f758 
EBP=00183aec ESP=00183ad0
Dec 13 18:09:28 pve2 QEMU[124616]: EIP=00292afa EFL=00200006 [-----P-] 
CPL=0 II=0 A20=1 SMM=0 HLT=0
Dec 13 18:09:28 pve2 QEMU[124616]: ES =0030 00000000 ffffffff 00c09300 
DPL=0 DS   [-WA]
Dec 13 18:09:28 pve2 QEMU[124616]: CS =0020 00000000 ffffffff 00c09b00 
DPL=0 CS32 [-RA]
Dec 13 18:09:28 pve2 QEMU[124616]: SS =0030 00000000 ffffffff 00c09300 
DPL=0 DS   [-WA]
Dec 13 18:09:28 pve2 QEMU[124616]: DS =0030 00000000 ffffffff 00c09300 
DPL=0 DS   [-WA]
Dec 13 18:09:28 pve2 QEMU[124616]: FS =0060 00023de0 0000ffff 00009300 
DPL=0 DS16 [-WA]
Dec 13 18:09:28 pve2 QEMU[124616]: GS =0060 00023de0 0000ffff 00009300 
DPL=0 DS16 [-WA]
Dec 13 18:09:28 pve2 QEMU[124616]: LDT=0000 00000000 00000000 00008200 
DPL=0 LDT
Dec 13 18:09:28 pve2 QEMU[124616]: TR =0040 00025260 00000077 00008900 
DPL=0 TSS32-avl
Dec 13 18:09:28 pve2 QEMU[124616]: GDT=     00184000 0000007f
Dec 13 18:09:28 pve2 QEMU[124616]: IDT=     00184080 000007ff
Dec 13 18:09:28 pve2 QEMU[124616]: CR0=80000011 CR2=00000000 
CR3=00185000 CR4=00000000
Dec 13 18:09:28 pve2 kernel: set kvm_intel.dump_invalid_vmcs=1 to dump 
internal KVM state.
Dec 13 18:09:28 pve2 QEMU[124616]: DR0=0000000000000000 
DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
Dec 13 18:09:28 pve2 QEMU[124616]: DR6=00000000ffff0ff0 DR7=0000000000000400
Dec 13 18:09:28 pve2 QEMU[124616]: EFER=0000000000000000
Dec 13 18:09:28 pve2 QEMU[124616]: Code=0c 89 08 89 7a 0c 8b 45 0c 83 45 
10 02 8b c8 2b cf 23 4a 08 <8b> 3a 8a 1c 0f 88 1c 07 40 41 ff 4d 10 83 
7d 10 00 7f ed 3b 45 f4 8b 7d fc 89 45 0c 0f 8c


Journal of the patched node when migrating the same VM from an unpatched
node:

Dec 13 18:12:17 pve1 QEMU[125150]: qemu-system-i386: Unknown savevm 
section or instance 'kvmclock' 0. Make sure that your current VM setup 
matches your saved VM setup, including any hotplugged devices
Dec 13 18:12:17 pve1 QEMU[125150]: qemu-system-i386: load of migration 
failed: Invalid argument