On Fri, Apr 12, 2024 at 1:44 PM David Matlack <dmatlack@xxxxxxxxxx> wrote: > > On 2024-04-01 11:29 PM, James Houghton wrote: > > Only handle the TDP MMU case for now. In other cases, if a bitmap was > > not provided, fallback to the slowpath that takes mmu_lock, or, if a > > bitmap was provided, inform the caller that the bitmap is unreliable. > > I think this patch will trigger a lockdep assert in > > kvm_tdp_mmu_age_gfn_range > kvm_tdp_mmu_handle_gfn > for_each_tdp_mmu_root > __for_each_tdp_mmu_root > kvm_lockdep_assert_mmu_lock_held > > ... because it walks tdp_mmu_roots without holding mmu_lock. Indeed, thanks. I'll make sure to build with CONFIG_LOCKDEP for the future versions and check for errors. > > Yu's patch[1] added a lockless walk to the TDP MMU. We'd need something > similar here and also update the comment above tdp_mmu_roots describing > how tdp_mmu_roots can be read locklessly. I'll add the macro / function to do the lockless walk of tdp_mmu_roots and explain why it is safe. Thanks for pointing out this big mistake. > [1] https://lore.kernel.org/kvmarm/ZItX64Bbx5vdjo9M@xxxxxxxxxx/
