On Wed, Jun 7, 2023 at 3:54 PM Nicholas Piggin <npiggin@xxxxxxxxx> wrote: > > On Mon Jun 5, 2023 at 4:48 PM AEST, Jordan Niethe wrote: > > There is existing support for nested guests on powernv hosts however the > > hcall interface this uses is not support by other PAPR hosts. > > I kind of liked it being called nested-HV v1 and v2 APIs as short and > to the point, but I suppose that's ambiguous with version 2 of the v1 > API, so papr is okay. What's the old API called in this scheme, then? > "Existing API" is not great after patches go upstream. Yes I was trying for a more descriptive name but it is just more confusing and I'm struggling for a better alternative. In the next revision I'll use v1 and v2. For version 2 of v1 we now call it v1.2 or something like that? > > And, you've probably explained it pretty well but slightly more of > a background first up could be helpful. E.g., > > A nested-HV API for PAPR has been developed based on the KVM-specific > nested-HV API that is upstream in Linux/KVM and QEMU. The PAPR API > had to break compatibility to accommodate implementation in other > hypervisors and partitioning firmware. > > And key overall differences > > The control flow and interrupt processing between L0, L1, and L2 > in the new PAPR API are conceptually unchanged. Where the old API > is almost stateless, the PAPR API is stateful, with the L1 registering > L2 virtual machines and vCPUs with the L0. Supervisor-privileged > register switching duty is now the responsibility for the L0, which > holds canonical L2 register state and handles all switching. This > new register handling motivates the "getters and setters" wrappers > ... I'll include something along those lines. Thanks, Jordan > > Thanks, > Nick >
