Re: [PATCH 2/2] KVM: x86/mmu: Recover NX Huge pages belonging to TDP MMU under MMU read lock

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

Hi Vipin,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 332d2c1d713e232e163386c35a3ba0c1b90df83f]

url:    https://github.com/intel-lab-lkp/linux/commits/Vipin-Sharma/KVM-x86-mmu-Split-NX-hugepage-recovery-flow-into-TDP-and-non-TDP-flow/20240814-091542
base:   332d2c1d713e232e163386c35a3ba0c1b90df83f
patch link:    https://lore.kernel.org/r/20240812171341.1763297-3-vipinsh%40google.com
patch subject: [PATCH 2/2] KVM: x86/mmu: Recover NX Huge pages belonging to TDP MMU under MMU read lock
config: x86_64-randconfig-123-20240814 (https://download.01.org/0day-ci/archive/20240815/202408150646.VV4z8Znl-lkp@intel.com/config)
compiler: clang version 18.1.5 (https://github.com/llvm/llvm-project 617a15a9eac96088ae5e9134248d8236e34b91b1)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240815/202408150646.VV4z8Znl-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/202408150646.VV4z8Znl-lkp@intel.com/

sparse warnings: (new ones prefixed by >>)
>> arch/x86/kvm/mmu/tdp_mmu.c:847:21: sparse: sparse: incompatible types in comparison expression (different address spaces):
   arch/x86/kvm/mmu/tdp_mmu.c:847:21: sparse:    unsigned long long [usertype] *
   arch/x86/kvm/mmu/tdp_mmu.c:847:21: sparse:    unsigned long long [noderef] [usertype] __rcu *
   arch/x86/kvm/mmu/tdp_mmu.c: note: in included file (through include/linux/rbtree.h, include/linux/mm_types.h, include/linux/mmzone.h, ...):
   include/linux/rcupdate.h:812:25: sparse: sparse: context imbalance in '__tdp_mmu_zap_root' - unexpected unlock
   arch/x86/kvm/mmu/tdp_mmu.c:1447:33: sparse: sparse: context imbalance in 'tdp_mmu_split_huge_pages_root' - unexpected unlock

vim +847 arch/x86/kvm/mmu/tdp_mmu.c

   819	
   820	static bool tdp_mmu_zap_sp(struct kvm *kvm, struct kvm_mmu_page *sp)
   821	{
   822		struct tdp_iter iter = {};
   823	
   824		lockdep_assert_held_read(&kvm->mmu_lock);
   825	
   826		/*
   827		 * This helper intentionally doesn't allow zapping a root shadow page,
   828		 * which doesn't have a parent page table and thus no associated entry.
   829		 */
   830		if (WARN_ON_ONCE(!sp->ptep))
   831			return false;
   832	
   833		iter.old_spte = kvm_tdp_mmu_read_spte(sp->ptep);
   834		iter.sptep = sp->ptep;
   835		iter.level = sp->role.level + 1;
   836		iter.gfn = sp->gfn;
   837		iter.as_id = kvm_mmu_page_as_id(sp);
   838	
   839	retry:
   840		/*
   841		 * Since mmu_lock is held in read mode, it's possible to race with
   842		 * another CPU which can remove sp from the page table hierarchy.
   843		 *
   844		 * No need to re-read iter.old_spte as tdp_mmu_set_spte_atomic() will
   845		 * update it in the case of failure.
   846		 */
 > 847		if (sp->spt != spte_to_child_pt(iter.old_spte, iter.level))
   848			return false;
   849	
   850		if (tdp_mmu_set_spte_atomic(kvm, &iter, SHADOW_NONPRESENT_VALUE))
   851			goto retry;
   852	
   853		return true;
   854	}
   855	

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