指令集

qemu64 是 qemu 的默认兼容性 CPU 模型，指令集很基础。但查看它的定义，居然包含 svm 这类虚拟化指令，这背后是 TCG 与 KVM 两种支持场景的差异。 现象 查看 qemu64 CPU 模型定义： cat /usr/share/libvirt/cpu_map/x86_qemu64.xml <cpus> <model name='qemu64'> <decode host='on' guest='on'/> <!-- These are supported only by TCG. KVM supports them only if the host does. So we leave them out: <feature name='abm'/> <feature name='lahf_lm'/> <feature name='popcnt'/> <feature name='sse4a'/> --> <feature name='apic'/> <feature name='clflush'/> <feature name='cmov'/> <feature name='cx16'/> <feature name='cx8'/> <feature name='de'/> <feature name='fpu'/> <feature name='fxsr'/> <feature name='lm'/> <feature name='mca'/> <feature name='mce'/> <feature name='mmx'/> <feature name='msr'/> <feature name='mtrr'/> <feature name='nx'/> <feature name='pae'/> <feature name='pat'/> <feature name='pge'/> <feature name='pni'/> <feature name='pse'/> <feature name='pse36'/> <feature name='sep'/> <feature name='sse'/> <feature name='sse2'/> <feature name='svm'/> <feature name='syscall'/> <feature name='tsc'/> </model> </cpus> 分析 qemu64 是 qemu 为了兼容性提供的默认 CPU 模型，指令集非常基础。 但有意思的是，它居然包含了 svm（AMD 的虚拟化扩展指令）。 ...

新系统跑不起来，报 “CPU does not support x86-64-v2”，根因是现代 OS 默认按较新指令集编译，而默认的 qemu64 模型只提供最基础指令。给虚拟机配上合适的 CPU 指令集就能解决。 现象 一台 primusos2403sp1x64 的虚拟机，没有配置 CPU 指令集的情况下，运行僵死。配置指令集后，就能正常运行了。 排查 用 virsh reset vm-example && virsh console vm-example 可以看到 glibc 打印的错误： [ 1.536627][ T1] Run /init as init process Fatal glibc error: CPU does not support x86-64-v2 [ 1.538855][ T1] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00 [ 1.540681][ T1] CPU: 6 PID: 1 Comm: init Not tainted 6.6.0-103.0.0.106.oe2403sp1.x86_64 #1 [ 1.542633][ T1] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 [ 1.545203][ T1] Call Trace: [ 1.545959][ T1] <TASK> [ 1.546568][ T1] dump_stack_lvl+0x32/0x50 [ 1.547593][ T1] panic+0x304/0x340 [ 1.548411][ T1] do_exit+0x3f4/0x410 [ 1.549284][ T1] do_group_exit+0x2d/0x80 [ 1.550272][ T1] __x64_sys_exit_group+0x14/0x20 [ 1.551151][ T1] do_syscall_64+0x55/0x100 [ 1.551963][ T1] entry_SYSCALL_64_after_hwframe+0x78/0xe2 [ 1.553370][ T1] RIP: 0033:0x7f40667d3db5 [ 1.557729][ T1] RSP: 002b:00007ffcb3db2f68 EFLAGS: 00000202 ORIG_RAX: 00000000000000e7 [ 1.559088][ T1] RAX: ffffffffffffffda RBX: 00007f40667cf490 RCX: 00007f40667d3db5 [ 1.560108][ T1] RDX: 0000000000000000 RSI: 00007ffcb3db2630 RDI: 000000000000007f [ 1.561078][ T1] RBP: 00007ffcb3db3140 R08: 0000000000000010 R09: 0000000000000000 [ 1.562048][ T1] R10: 0000000000000001 R11: 0000000000000202 R12: 00007f40667e2ab0 [ 1.563025][ T1] R13: 0000000000000000 R14: 0000000000000000 R15: 00007f40667b4000 [ 1.563990][ T1] </TASK> [ 1.564790][ T1] Kernel Offset: 0x38c00000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff) [ 1.566210][ T1] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x00007f00 ]--- 根因 这是已知问题：现代操作系统都开启了指令集优化，纯 qemu 的模拟指令无法满足运行的基本要求，必须配上指令集才能运行。 ...