Re: [PATCH 0/4] Fix RCU warnings in TDP MMU

[Paolo Bonzini]

On 12/03/21 00:16, Ben Gardon wrote:
> The Linux Test Robot found a few RCU warnings in the TDP MMU:
> https://www.spinics.net/lists/kernel/msg3845500.html
> https://www.spinics.net/lists/kernel/msg3845521.html
>
> Fix these warnings and cleanup a hack in tdp_mmu_iter_cond_resched.
>
> Tested by compiling as suggested in the test robot report and confirmed that
> the warnings go away with this series applied. Also ran kvm-unit-tests on an
> Intel Skylake machine with the TDP MMU enabled and confirmed that the series
> introduced no new failures.
>
> Ben Gardon (4):
>    KVM: x86/mmu: Fix RCU usage in handle_removed_tdp_mmu_page
>    KVM: x86/mmu: Fix RCU usage for tdp_iter_root_pt
>    KVM: x86/mmu: Fix RCU usage when atomically zapping SPTEs
>    KVM: x86/mmu: Factor out tdp_iter_return_to_root
>
>   arch/x86/kvm/mmu/tdp_iter.c | 34 +++++++++++++++++++++++++---------
>   arch/x86/kvm/mmu/tdp_iter.h |  3 ++-
>   arch/x86/kvm/mmu/tdp_mmu.c  | 19 +++++++++++--------
>   3 files changed, 38 insertions(+), 18 deletions(-)

Mostly good but Sean's suggestion in patch 2 is indeed better.  There's 
enough changes that I'll wait for a v2 from you.  Thanks!

Paolo