From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Date: Fri, May 3, 2019 at 3:25 AM To: Aaron Lewis Cc: Peter Shier, <pbonzini@xxxxxxxxxx>, <rkrcmar@xxxxxxxxxx>, <jmattson@xxxxxxxxxx>, <marcorr@xxxxxxxxxx>, <kvm@xxxxxxxxxxxxxxx> > Aaron Lewis <aaronlewis@xxxxxxxxxx> writes: > > > Move call to nested_enable_evmcs until after free_nested() is complete. > > > > Signed-off-by: Aaron Lewis <aaronlewis@xxxxxxxxxx> > > Reviewed-by: Marc Orr <marcorr@xxxxxxxxxx> > > Reviewed-by: Peter Shier <pshier@xxxxxxxxxx> > > --- > > arch/x86/kvm/vmx/nested.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c > > index 081dea6e211a..3b39c60951ac 100644 > > --- a/arch/x86/kvm/vmx/nested.c > > +++ b/arch/x86/kvm/vmx/nested.c > > @@ -5373,9 +5373,6 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu, > > if (kvm_state->format != 0) > > return -EINVAL; > > > > - if (kvm_state->flags & KVM_STATE_NESTED_EVMCS) > > - nested_enable_evmcs(vcpu, NULL); > > - > > if (!nested_vmx_allowed(vcpu)) > > return kvm_state->vmx.vmxon_pa == -1ull ? 0 : -EINVAL; > > > > @@ -5417,6 +5414,9 @@ static int vmx_set_nested_state(struct kvm_vcpu *vcpu, > > if (kvm_state->vmx.vmxon_pa == -1ull) > > return 0; > > > > + if (kvm_state->flags & KVM_STATE_NESTED_EVMCS) > > + nested_enable_evmcs(vcpu, NULL); > > + > > vmx->nested.vmxon_ptr = kvm_state->vmx.vmxon_pa; > > ret = enter_vmx_operation(vcpu); > > if (ret) > > nested_enable_evmcs() doesn't do much, actually, in case it was > previously enabled it doesn't do anything and in case it wasn't ordering > with free_nested() (where you're aiming at nested_release_evmcs() I > would guess) shouldn't matter. So could you please elaborate (better in > the commit message) why do we need this re-ordered? My guess is that > you'd like to perform checks for e.g. 'vmx.vmxon_pa == -1ull' before > we actually start doing any changes but let's clarify that. > > Thanks! > > -- > Vitaly There are two reasons for doing this: 1. We don't want to set new state if we are going to leave nesting and exit the function (ie: vmx.vmxon_pa = -1), like you pointed out. 2. To be more future proof, we don't want to set new state before tearing down state. This could cause conflicts down the road. I can add this to the commit message if there are no objections to these points.
