Paolo Bonzini <pbonzini@xxxxxxxxxx> writes: > On 16/01/2018 14:58, Vitaly Kuznetsov wrote: >>> Haven't looked into the details, but we have to watch out for other >>> VCPUs trying to modify that vmcs12. >>> >>> Basically because other VCPUs could try to modify values in vmcs12 while >>> we are currently building vmcs02. Nasty races could result in us copying >>> stuff (probably unchecked) into vmcs02 and therefore running something >>> that was not intended. >>> >> I don't think we share VMCS among vCPUs, do we? > > VMCS is just memory, so who knows what a malicious L1 guest will do. > But for vmread/vmwrite we can go through hypervisor memory, for > enlightened VMCS we cannot. > True; not sure if Hyper-V actually copies the data to some internal storage, probably it does. TLFS explicitly forbids making the same enlightened VMCS active on several vCPUs simultaneously but again, this is just memory... -- Vitaly
