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Another thing >>> is that if firmware isn't aware that 1:N interrupts can (or should) >>> wake-up a CPU from sleep, bad things will happen. Given that nobody >>> uses 1:N, you can bet that any bit of privileged SW (TF-A, >>> hypervisors) is likely to be buggy (I've already spotted bugs in KVM >>> around this). >> >> Thierry, do we ever hotplug CPUs on this device? If not, I am wondering if >> something like this, for now, could only be enabled for devices that don't >> hotplug CPUs. Maybe tied to the kernel config (ie. CONFIG_HOTPLUG_CPU)? Just >> a thought ... > > I've only had limited exposure to this, so I don't know all of the use- > cases. People can buy these devices and do anything they want with it, > so I think we have to account for the general case. Yes, but the point I was trying to make that you can prevent this from being used if CPU hotplug is enabled in the kernel and initially limit to configurations where this feature would/could be enabled. So you take CPU hotplug out of the equation (initially). Of course someone can hack the kernel and do what they want, but there is nothing you can do about that. Jon -- nvpublic