On Thu, Jul 13, 2023 at 07:48:20AM +0000, Huang, Kai wrote: > I found below comment in KVM code: > > > + * See arch/x86/kvm/vmx/vmenter.S: > > + * > > + * In theory, a L1 cache miss when restoring register from stack > > + * could lead to speculative execution with guest's values. > > And KVM explicitly does XOR for the registers that gets "pop"ed almost > instantly, so I followed. > > But to be honest I don't quite understand this. :-) Urgh, I suppose that actually makes sense. Since pop is a load it might continue speculation with the previous value. Whereas the xor-clear idiom is impossible to speculate through. Oh well...
