On Tue, Mar 21, 2023, Sean Christopherson wrote: > On Tue, Mar 21, 2023, Vipin Sharma wrote: > > On Mon, Mar 20, 2023 at 5:41 PM Sean Christopherson <seanjc@xxxxxxxxxx> wrote: > > > > > > On Fri, Mar 17, 2023, Sean Christopherson wrote: > > > > Did a cursory glance, looks good. I'll do a more thorough pass next week and get > > > > it queued up if all goes well. No need for a v4 at this point, I'll fixup David's > > > > various nits when applying. > > > > > > Ooof, that ended up being painful. In hindsight, I should have asked for a v4, > > > but damage done, and it's my fault for throwing you a big blob of code in the > > > first place. > > > > > > I ended up splitting the "interesting" patches into three each: > > > > > > 1. Switch to the atomic-AND > > > 2. Drop the access-tracking / dirty-logging (as appropriate) > > > 3. Drop the call to __handle_changed_spte() > > > > > > because logically they are three different things (although obviously related). > > > > > > I have pushed the result to kvm-x86/mmu, but haven't merged to kvm-x86/next or > > > sent thanks because it's not yet tested. I'll do testing tomorrow, but if you > > > can take a look in the meantime to make sure I didn't do something completely > > > boneheaded, it'd be much appreciated. > > > > > > Thanks for refactoring the patches. I reviewed the commits, no obvious > > red flags from my side. Few small nits I found: > > > > commit e534a94eac07 ("KVM: x86/mmu: Use kvm_ad_enabled() to determine > > if TDP MMU SPTEs need wrprot") > > - kvm_ad_enabled() should be outside the loop. > > Hmm, I deliberately left it inside the loop, but I agree that it would be better > to hoist it out in that commit. > > > commit 69032b5d71ef (" KVM: x86/mmu: Atomically clear SPTE dirty state > > in the clear-dirty-log flow") > > - MMU_WARN_ON(kvm_ad_enabled() && > > spte_ad_need_write_protect(iter.old_spte) should be after > > if(iter.level > PG_LEVEL_4k...) > > Ah, hrm. This was also deliberate, but looking at the diff I agree that relative > to the diff, it's an unnecessary/unrelated change. I think what I'll do is > land the assertion above the "if (iter.level > PG_LEVEL_4K ||" in the above > commit that switches to kvm_ad_enabled(). That way there shouldn't be any change > for the assertion in this commit. Aha! Even better, split this into yet one more patch to dedup the guts before switching to the atomic-AND, and give clear_dirty_gfn_range() the same treatment. That further isolates the changes, provides solid justification for hoisting the kvm_ad_enabled() check out of the loop (it's basically guaranteed to be a single memory read that hits the L1), and keeps clear_dirty_gfn_range() and clear_dirty_pt_masked() as similar as is reasonably possible. Speaking of which, I'll send a patch to remove the redundant is_shadow_present_pte() check in clear_dirty_gfn_range(), that's already handled by tdp_root_for_each_leaf_pte().