This reverts commit a943ac50d10aac96dca63d0460365a699d41fdd0.
Fine-grained VMX feature enablement in QEMU broke live migration with
nested guest:
(qemu) qemu-kvm: error: failed to set MSR 0x48e to 0xfff9fffe04006172
The problem is that QEMU does KVM_SET_NESTED_STATE before KVM_SET_MSRS,
although it can probably be changed.
RFC. I think the check for vmx->nested.vmxon is legitimate for everything
but restore so removing it (what I do with the revert) is likely a no-go.
I'd like to gather opinions on the proper fix: should we somehow check
that the vCPU is in 'restore' start (has never being run) and make
KVM_SET_MSRS pass or should we actually mandate that KVM_SET_NESTED_STATE
is run after KVM_SET_MSRS by userspace?
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 4aea7d304beb..bb8afe0c5e7f 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -1321,13 +1321,6 @@ int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
- /*
- * Don't allow changes to the VMX capability MSRs while the vCPU
- * is in VMX operation.
- */
- if (vmx->nested.vmxon)
- return -EBUSY;
-
switch (msr_index) {
case MSR_IA32_VMX_BASIC:
return vmx_restore_vmx_basic(vmx, data);
--
2.24.1
