Comment 59 for bug 1788098

Juerg Haefliger (juergh) wrote :

Leonardo, can you elaborate on the 'other possible issues'? We're hesitant to pull 18 patches into a stable kernel under the assumption that they *might* fix some *potential* issues, without clear evidence. If you can test the single-patch kernel and report back that there are still issues then that's a much stronger case for the other patches.

Commit 'KVM: PPC: Book3S HV: Avoid crash from THP collapse during radix page fault' that you're asking for requires all these additional backports to apply cleanly. Which makes me wonder if we're not actually introducing a problem with these backports just to fix it again later. Not saying that's the case, just wondering...

Also, the following seem to be totally unrelated and unnecessary:
  - KVM: PPC: Remove unused kvm_unmap_hva callback
  - powerpc/mm/radix: Remove unused code

While looking through the patches I also noticed that the following is the second patch of a series of 11 but it's the only one from the series that you're backporting.
  - powerpc/kvm: Switch kvm pmd allocator to custom allocator
Its commit message mentions subsequent patches of that series so I'm wondering why we need/want only this single patch??

Remember that we have to support this kernel for years and years to come so we only want to backport the absolute necessary.

Lastly and FYI, the following is the minimal subset of your patches that all cherry-pick cleanly:
  - KVM: PPC: Book3S HV: Avoid crash from THP collapse during radix page fault
  - KVM: PPC: Book3S HV: Don't use compound_order to determine host mapping size
  - KVM: PPC: Book3S HV: Use correct pagesize in kvm_unmap_radix()
  - KVM: PPC: Book3S HV: radix: Refine IO region partition scope attributes
  - KVM: PPC: Book3S HV: Use __gfn_to_pfn_memslot() in page fault handler
  - KVM: PPC: Book3S HV: Handle 1GB pages in radix page fault handler
  - KVM: PPC: Book3S HV: Streamline setting of reference and change bits
  - KVM: PPC: Book3S HV: Radix page fault handler optimizations

Please provide some context why we need all the above (and potentially more).