Re: Proposed deprecation of N extension

Gernot <gernot.heiser@...>

On 5 Jun 2021, at 12:59, Jonathan Behrens <behrensj@...> wrote:

To the point about Linux letting processes handle interrupts themselves, this is actually already possible today... using KVM. If you create a virtual machine, then you can setup passthrough so that a hardware device and the associated interrupts are handled within it. In fact, if you go through the same exercise of comparing CSRs that I did above, you'll see that a M/S/U + N system is actually very similar to a M/HS/VS/U system with vsatp hardwired to zero.

VMs are more heavyweight than processes, and slipping a hypervisor underneath isn’t always a suitable approach. In terms of security, putting KVM underneath vastly *increases* the size of the trusted computing base.


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