Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [RFC 0/6] Enlightened VMCS support for KVM on Hyper-V | Date | Tue, 16 Jan 2018 15:43:56 +0100 |
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Paolo Bonzini <pbonzini@redhat.com> 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
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