Hi, all I encounterd a bug when I try to migrate a windows vm. Enviroment information: host A: cpu E5620(model WestmereEP without flag xsave) host B: cpu E5-2643(model SandyBridgeEP with xsave)
The reproduce steps is : 1. Start a windows 2008 vm with -cpu host(which means host-passthrough). 2. Migrate the vm to host B when cr4.OSXSAVE=0 (successfully). 3. Vm runs on host B for a while so that cr4.OSXSAVE changes to 1. 4. Then migrate the vm to host A (successfully), but vm was paused, and qemu printed log as followed: KVM: entry failed, hardware error 0x80000021 If you're running a guest on an Intel machine without unrestricted mode support, the failure can be most likely due to the guest entering an invalid state for Intel VT. For example, the guest maybe running in big real mode which is not supported on less recent Intel processors. EAX=019b3bb0 EBX=01a3ae80 ECX=01a61ce8 EDX=00000000 ESI=01a62000 EDI=00000000 EBP=00000000 ESP=01718b20 EIP=0185d982 EFL=00000286 [--S--P-] CPL=0 II=0 A20=1 SMM=0 HLT=0 ES =0000 00000000 0000ffff 00009300 CS =f000 ffff0000 0000ffff 00009b00 SS =0000 00000000 0000ffff 00009300 DS =0000 00000000 0000ffff 00009300 FS =0000 00000000 0000ffff 00009300 GS =0000 00000000 0000ffff 00009300 LDT=0000 00000000 0000ffff 00008200 TR =0000 00000000 0000ffff 00008b00 GDT= 00000000 0000ffff IDT= 00000000 0000ffff CR0=60000010 CR2=00000000 CR3=00000000 CR4=00000000 DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000 DR6=00000000ffff0ff0 DR7=0000000000000400 EFER=0000000000000000 Code=00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 <00> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 I have found that problem happened when kvm_put_sregs returns err -22(called by kvm_arch_put_registers(qemu)). Because kvm_arch_vcpu_ioctl_set_sregs(kvm-mod) checked that guest_cpuid_has no X86_FEATURE_XSAVE but cr4.OSXSAVE=1. So should we cancel migration when kvm_arch_put_registers returns error?