On Thu, Apr 1, 2021 at 2:37 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 31/03/21 23:08, Ben Gardon wrote: > > Protect the contents of the TDP MMU roots list with RCU in preparation > > for a future patch which will allow the iterator macro to be used under > > the MMU lock in read mode. > > > > Signed-off-by: Ben Gardon<bgardon@xxxxxxxxxx> > > --- > > arch/x86/kvm/mmu/tdp_mmu.c | 64 +++++++++++++++++++++----------------- > > 1 file changed, 36 insertions(+), 28 deletions(-) > > > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > > + spin_lock(&kvm->arch.tdp_mmu_pages_lock); > > + list_del_rcu(&root->link); > > + spin_unlock(&kvm->arch.tdp_mmu_pages_lock); > > > Please update the comment above tdp_mmu_pages_lock in > arch/x86/include/asm/kvm_host.h as well. Ah yes, thank you for catching that. Will do. > > > /* Only safe under the MMU lock in write mode, without yielding. */ > > #define for_each_tdp_mmu_root(_kvm, _root) \ > > - list_for_each_entry(_root, &_kvm->arch.tdp_mmu_roots, link) > > + list_for_each_entry_rcu(_root, &_kvm->arch.tdp_mmu_roots, link, \ > > + lockdep_is_held_write(&kvm->mmu_lock)) > > This should also add "... || > lockdep_is_help(&kvm->arch.tdp_mmu_pages_lock)", if only for > documentation purposes. Good idea. I hope we never have a function try to protect its loop over the roots with that lock, but it would be correct. > > Paolo >
