On Sun, Mar 10, 2024 at 9:46 PM Oliver Upton <oliver.upton@xxxxxxxxx> wrote: > > Hey, > > Thanks Sean for bringing this up on the list, didn't have time for a lot > of upstream stuffs :) > > On Fri, Mar 08, 2024 at 04:46:32PM -0800, David Matlack wrote: > > On 2024-03-08 02:07 PM, Sean Christopherson wrote: > > > On Thu, Feb 15, 2024, Anish Moorthy wrote: > > > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > > > > index 9f5d45c49e36..bf7bc21d56ac 100644 > > > > --- a/Documentation/virt/kvm/api.rst > > > > +++ b/Documentation/virt/kvm/api.rst > > > > @@ -1353,6 +1353,7 @@ yet and must be cleared on entry. > > > > #define KVM_MEM_LOG_DIRTY_PAGES (1UL << 0) > > > > #define KVM_MEM_READONLY (1UL << 1) > > > > #define KVM_MEM_GUEST_MEMFD (1UL << 2) > > > > + #define KVM_MEM_EXIT_ON_MISSING (1UL << 3) > > > > > > David M., > > > > > > Before this gets queued anywhere, a few questions related to the generic KVM > > > userfault stuff you're working on: > > > > > > 1. Do you anticipate reusing KVM_MEM_EXIT_ON_MISSING to communicate that a vCPU > > > should exit to userspace, even for guest_memfd? Or are you envisioning the > > > "data invalid" gfn attribute as being a superset? > > > > > > We danced very close to this topic in the PUCK call, but I don't _think_ we > > > ever explicitly talked about whether or not KVM_MEM_EXIT_ON_MISSING would > > > effectively be obsoleted by a KVM_SET_MEMORY_ATTRIBUTES-based "invalid data" > > > flag. > > > > > > I was originally thinking that KVM_MEM_EXIT_ON_MISSING would be re-used, > > > but after re-watching parts of the PUCK recording, e.g. about decoupling > > > KVM from userspace page tables, I suspect past me was wrong. > > > > No I don't anticipate reusing KVM_MEM_EXIT_ON_MISSING. > > > > The plan is to introduce a new gfn attribute and exit to userspace based > > on that. I do forsee having an on/off switch for the new attribute, but > > it wouldn't make sense to reuse KVM_MEM_EXIT_ON_MISSING for that. > > With that in mind, unless someone else has a usecase for the > KVM_MEM_EXIT_ON_MISSING behavior my *strong* preference is that we not > take this bit of the series upstream. The "memory fault" UAPI should > still be useful when the KVM userfault stuff comes along. > > Anish, apologies, you must have whiplash from all the bikeshedding, > nitpicking, and other fun you've been put through on this series. Thanks > for being patient. No worries- I got a lot of patient (and much-needed) review as well :). And I understand not wanting to add an eternal feature when something better is coming down the line. On Mon, Mar 11, 2024 at 9:36 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > Oh, and I'll plan on grabbing patches 1-4 for 6.10. I think patches 10/11/12 are useful changes to the selftest that make sense to merge even with KVM_MEM_EXIT_ON_MISSING being mothballed- they should rebase without any issues. And the annotations on the stage-2 fault handlers seem like they should still be added, but I suppose David can do that with his series.
