On Fri, Dec 15, 2023 at 12:54 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > On Fri, Dec 15, 2023, Vineeth Remanan Pillai wrote: > > > You are basically proposing that KVM bounce-buffer data between guest and host. > > > I'm saying there's no _technical_ reason to use a bounce-buffer, just do zero copy. > > > > > I was also meaning zero copy only. The help required from the kvm side is: > > - Pass the address of the shared memory to bpf programs/scheduler once > > the guest sets it up. > > - Invoke scheduler registered callbacks on events like VMEXIT, > > VEMENTRY, interrupt injection etc. Its the job of guest and host > > paravirt scheduler to interpret the shared memory contents and take > > actions. > > > > I admit current RFC doesn't strictly implement hooks and callbacks - > > it calls sched_setscheduler in place of all callbacks that I mentioned > > above. I guess this was your strongest objection. > > Ya, more or less. > > > As you mentioned in the reply to Joel, if it is fine for kvm to allow > > hooks into events (VMEXIT, VMENTRY, interrupt injection etc) then, it > > makes it easier to develop the ABI I was mentioning and have the hooks > > implemented by a paravirt scheduler. We shall re-design the > > architecture based on this for v2. > > Instead of going straight to a full blown re-design, can you instead post slightly > more incremental RFCs? E.g. flesh out enough code to get a BPF program attached > and receiving information, but do NOT wait until you have fully working setup > before posting the next RFC. > Sure, makes sense. > There are essentially four-ish things to sort out: > > 1. Where to insert/modify hooks in KVM > 2. How KVM exposes KVM-internal information through said hooks > 3. How a BPF program can influence the host scheduler > 4. The guest/host ABI > > #1 and #2 are largely KVM-only, and I think/hope we can get a rough idea of how > to address them before moving onto #3 and #4 (assuming #3 isn't already a solved > problem). Agreed. Will start with the kvm side and keep you posted on the progress. Thanks, Vineeth
