It depends on whether it's an attack against HVM hypervisors or not.
If it, like it seems, is just an attack on OS kernels and PV hypervisors, you can simply turn off the mitigation, since nowadays kernel security is mostly useless (and Linux is likely full of exploitable bugs anyway, so memory protection doesn't really do that much other that protecting against accidental crashes, which isn't changed by this).
Even if it's an attack against hypervisors any large deployment can simply use reserved machines and it won't have a significant cost.
If it, like it seems, is just an attack on OS kernels and PV hypervisors, you can simply turn off the mitigation, since nowadays kernel security is mostly useless (and Linux is likely full of exploitable bugs anyway, so memory protection doesn't really do that much other that protecting against accidental crashes, which isn't changed by this).
Even if it's an attack against hypervisors any large deployment can simply use reserved machines and it won't have a significant cost.