Re: [PATCH v4 1/7] KVM: x86/mmu: Track TDP MMU NX huge pages separately

[kernel test robot <lkp@intel.com>]

Hi James,

kernel test robot noticed the following build errors:

[auto build test ERROR on 8046d29dde17002523f94d3e6e0ebe486ce52166]

url:    https://github.com/intel-lab-lkp/linux/commits/James-Houghton/KVM-x86-mmu-Track-TDP-MMU-NX-huge-pages-separately/20250614-042620
base:   8046d29dde17002523f94d3e6e0ebe486ce52166
patch link:    https://lore.kernel.org/r/20250613202315.2790592-2-jthoughton%40google.com
patch subject: [PATCH v4 1/7] KVM: x86/mmu: Track TDP MMU NX huge pages separately
config: i386-randconfig-003-20250614 (https://download.01.org/0day-ci/archive/20250614/202506142050.kfDUdARX-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250614/202506142050.kfDUdARX-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202506142050.kfDUdARX-lkp@intel.com/

All errors (new ones prefixed by >>):

   arch/x86/kvm/mmu/mmu.c: In function 'kvm_recover_nx_huge_pages':
>> arch/x86/kvm/mmu/mmu.c:7609:38: error: 'KVM_TDP_MMU' undeclared (first use in this function)
    7609 |                 else if (mmu_type == KVM_TDP_MMU)
         |                                      ^~~~~~~~~~~
   arch/x86/kvm/mmu/mmu.c:7609:38: note: each undeclared identifier is reported only once for each function it appears in


vim +/KVM_TDP_MMU +7609 arch/x86/kvm/mmu/mmu.c

  7537	
  7538	static void kvm_recover_nx_huge_pages(struct kvm *kvm,
  7539					      enum kvm_mmu_type mmu_type)
  7540	{
  7541		unsigned long to_zap = nx_huge_pages_to_zap(kvm, mmu_type);
  7542		struct list_head *nx_huge_pages;
  7543		struct kvm_memory_slot *slot;
  7544		struct kvm_mmu_page *sp;
  7545		LIST_HEAD(invalid_list);
  7546		bool flush = false;
  7547		int rcu_idx;
  7548	
  7549		nx_huge_pages = &kvm->arch.possible_nx_huge_pages[mmu_type].pages;
  7550	
  7551		rcu_idx = srcu_read_lock(&kvm->srcu);
  7552		write_lock(&kvm->mmu_lock);
  7553	
  7554		/*
  7555		 * Zapping TDP MMU shadow pages, including the remote TLB flush, must
  7556		 * be done under RCU protection, because the pages are freed via RCU
  7557		 * callback.
  7558		 */
  7559		rcu_read_lock();
  7560	
  7561		for ( ; to_zap; --to_zap) {
  7562			if (list_empty(nx_huge_pages))
  7563				break;
  7564	
  7565			/*
  7566			 * We use a separate list instead of just using active_mmu_pages
  7567			 * because the number of shadow pages that be replaced with an
  7568			 * NX huge page is expected to be relatively small compared to
  7569			 * the total number of shadow pages.  And because the TDP MMU
  7570			 * doesn't use active_mmu_pages.
  7571			 */
  7572			sp = list_first_entry(nx_huge_pages,
  7573					      struct kvm_mmu_page,
  7574					      possible_nx_huge_page_link);
  7575			WARN_ON_ONCE(!sp->nx_huge_page_disallowed);
  7576			WARN_ON_ONCE(!sp->role.direct);
  7577	
  7578			/*
  7579			 * Unaccount and do not attempt to recover any NX Huge Pages
  7580			 * that are being dirty tracked, as they would just be faulted
  7581			 * back in as 4KiB pages. The NX Huge Pages in this slot will be
  7582			 * recovered, along with all the other huge pages in the slot,
  7583			 * when dirty logging is disabled.
  7584			 *
  7585			 * Since gfn_to_memslot() is relatively expensive, it helps to
  7586			 * skip it if it the test cannot possibly return true.  On the
  7587			 * other hand, if any memslot has logging enabled, chances are
  7588			 * good that all of them do, in which case unaccount_nx_huge_page()
  7589			 * is much cheaper than zapping the page.
  7590			 *
  7591			 * If a memslot update is in progress, reading an incorrect value
  7592			 * of kvm->nr_memslots_dirty_logging is not a problem: if it is
  7593			 * becoming zero, gfn_to_memslot() will be done unnecessarily; if
  7594			 * it is becoming nonzero, the page will be zapped unnecessarily.
  7595			 * Either way, this only affects efficiency in racy situations,
  7596			 * and not correctness.
  7597			 */
  7598			slot = NULL;
  7599			if (atomic_read(&kvm->nr_memslots_dirty_logging)) {
  7600				struct kvm_memslots *slots;
  7601	
  7602				slots = kvm_memslots_for_spte_role(kvm, sp->role);
  7603				slot = __gfn_to_memslot(slots, sp->gfn);
  7604				WARN_ON_ONCE(!slot);
  7605			}
  7606	
  7607			if (slot && kvm_slot_dirty_track_enabled(slot))
  7608				unaccount_nx_huge_page(kvm, sp);
> 7609			else if (mmu_type == KVM_TDP_MMU)
  7610				flush |= kvm_tdp_mmu_zap_sp(kvm, sp);
  7611			else
  7612				kvm_mmu_prepare_zap_page(kvm, sp, &invalid_list);
  7613			WARN_ON_ONCE(sp->nx_huge_page_disallowed);
  7614	
  7615			if (need_resched() || rwlock_needbreak(&kvm->mmu_lock)) {
  7616				kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
  7617				rcu_read_unlock();
  7618	
  7619				cond_resched_rwlock_write(&kvm->mmu_lock);
  7620				flush = false;
  7621	
  7622				rcu_read_lock();
  7623			}
  7624		}
  7625		kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, flush);
  7626	
  7627		rcu_read_unlock();
  7628	
  7629		write_unlock(&kvm->mmu_lock);
  7630		srcu_read_unlock(&kvm->srcu, rcu_idx);
  7631	}
  7632	

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