On 11/10/21 11:00, Maxim Levitsky wrote:
+ /*
+ * The vcpu might currently contain L2's IA32_EFER, due to the way
+ * some userspace kvm users (e.g qemu) restore nested state.
+ *
+ * To fix this, restore its IA32_EFER to the value it would have
+ * after VM exit from the nested guest.
+ *
+ */
+
+ vcpu->arch.efer = nested_vmx_get_vmcs12_host_efer(vcpu, vmcs12);
+
In principle the value of LOAD_HOST_EFER on exit need not be the same as
on entry. But you don't need all of EFER, only EFER.LME/EFER.LMA, and
those two bits must match ("the values of the LMA and LME bits in the
field must each be that of the “host address-space size” VM-exit
control" from the "Checks on Host Control Registers, MSRs, and SSP";
plus the "Checks Related to Address-Space Size").
At least it's worth adjusting the comment to explain that. But the root
cause of the issue is just nested_vmx_check_* accessing vcpu->arch. So
you can instead:
- split out of nested_vmx_check_host_state a new function
nested_vmx_check_address_state_size that does
#ifdef CONFIG_X86_64
if (CC(!!(vmcs12->vm_exit_controls & VM_EXIT_HOST_ADDR_SPACE_SIZE) !=
!!(vcpu->arch.efer & EFER_LMA)))
return -EINVAL;
#endif
return 0;
- call it from vmentry but not from migration
- in nested_vmx_check_host_state, assign ia32e from
vmcs12->vm_exit_controls instead of vcpu->arch.efer
Paolo
