kernel: x86/fpu: KVM: Set the base guest FPU uABI size to sizeof(struct kvm_xsave)

In the Linux kernel, the following vulnerability has been resolved: x86/fpu: KVM: Set the base guest FPU uABI size to sizeofstruct kvmxsave Set the starting uABI size of KVM's guest FPU to 'struct kvmxsave', i.e. to KVM's historical uABI size. When saving FPU state for usersapce, KVM well, now th...