KVM: VMX: Fix host MSR_KERNEL_GS_BASE corruption
enter_lmode() and exit_lmode() modify the guest's EFER.LMA before calling
vmx_set_efer(). However, the latter function depends on the value of EFER.LMA
to determine whether MSR_KERNEL_GS_BASE needs reloading, via
vmx_load_host_state(). With EFER.LMA changing under its feet, it took the
wrong choice and corrupted userspace's %gs.
This causes 32-on-64 host userspace to fault.
Fix not touching EFER.LMA; instead ask vmx_set_efer() to change it.
Signed-off-by: Avi Kivity <avi@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 859a01a..ee03679 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1744,18 +1744,15 @@
(guest_tr_ar & ~AR_TYPE_MASK)
| AR_TYPE_BUSY_64_TSS);
}
- vcpu->arch.efer |= EFER_LMA;
- vmx_set_efer(vcpu, vcpu->arch.efer);
+ vmx_set_efer(vcpu, vcpu->arch.efer | EFER_LMA);
}
static void exit_lmode(struct kvm_vcpu *vcpu)
{
- vcpu->arch.efer &= ~EFER_LMA;
-
vmcs_write32(VM_ENTRY_CONTROLS,
vmcs_read32(VM_ENTRY_CONTROLS)
& ~VM_ENTRY_IA32E_MODE);
- vmx_set_efer(vcpu, vcpu->arch.efer);
+ vmx_set_efer(vcpu, vcpu->arch.efer & ~EFER_LMA);
}
#endif