On Fri, Sep 14, 2018 at 12:49 AM, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote: > Jim Mattson <jmattson@xxxxxxxxxx> writes: > >> On Thu, Sep 13, 2018 at 10:05 AM, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> wrote: >>> It is perfectly valid for a guest to do VMXON and not do VMPTRLD. This >>> state needs to be preserved on migration. >>> >>> Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> >>> --- >>> arch/x86/kvm/vmx.c | 15 ++++++++------- >>> 1 file changed, 8 insertions(+), 7 deletions(-) >>> >>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c >>> index d3297fadf7ed..25a25fff8dd9 100644 >>> --- a/arch/x86/kvm/vmx.c >>> +++ b/arch/x86/kvm/vmx.c >>> @@ -14482,13 +14482,6 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu, >>> if (!page_address_valid(vcpu, kvm_state->vmx.vmxon_pa)) >>> return -EINVAL; >>> >>> - if (kvm_state->size < sizeof(kvm_state) + sizeof(*vmcs12)) >>> - return -EINVAL; >>> - >>> - if (kvm_state->vmx.vmcs_pa == kvm_state->vmx.vmxon_pa || >>> - !page_address_valid(vcpu, kvm_state->vmx.vmcs_pa)) >>> - return -EINVAL; >>> - >>> if ((kvm_state->vmx.smm.flags & KVM_STATE_NESTED_SMM_GUEST_MODE) && >>> (kvm_state->flags & KVM_STATE_NESTED_GUEST_MODE)) >>> return -EINVAL; >>> @@ -14510,6 +14503,14 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu, >>> if (ret) >>> return ret; >>> >>> + /* Empty 'VMXON' state is permitted */ >>> + if (kvm_state->size < sizeof(kvm_state) + sizeof(*vmcs12)) >>> + return 0; >> >> In the original version of this code, the early exit is: >> >> if (kvm_state.vmcs_pa == -1ull) >> return 0; > > Time to restore the status quo :-) > > In any case this early exit should be done after enter_vmx_operation() > as even without a valid VMCS we need to preserve VMXON state (e.g. Linux > with loaded KVM but without any guests running). Yes. That's also the way it was originally.
