KVM: x86/mmu: Factor out spte atomic bit clearing routine

This new function, tdp_mmu_clear_spte_bits_atomic(), will be used in a
follow-up patch to enable lockless Accessed bit clearing.

Signed-off-by: James Houghton <jthoughton@google.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Link: https://lore.kernel.org/r/20250204004038.1680123-4-jthoughton@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/mmu/tdp_iter.h b/arch/x86/kvm/mmu/tdp_iter.h
index 047b7833365394c8c7199484831133b64874b1c2..9135b035fa40f6777c9769abb337995a5c62a7cd 100644 (file)
--- a/arch/x86/kvm/mmu/tdp_iter.h
+++ b/arch/x86/kvm/mmu/tdp_iter.h
@@ -25,6 +25,13 @@ static inline u64 kvm_tdp_mmu_write_spte_atomic(tdp_ptep_t sptep, u64 new_spte)
        return xchg(rcu_dereference(sptep), new_spte);
 }
 
+static inline u64 tdp_mmu_clear_spte_bits_atomic(tdp_ptep_t sptep, u64 mask)
+{
+       atomic64_t *sptep_atomic = (atomic64_t *)rcu_dereference(sptep);
+
+       return (u64)atomic64_fetch_and(~mask, sptep_atomic);
+}
+
 static inline void __kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 new_spte)
 {
        KVM_MMU_WARN_ON(is_ept_ve_possible(new_spte));
@@ -63,12 +70,8 @@ static inline u64 kvm_tdp_mmu_write_spte(tdp_ptep_t sptep, u64 old_spte,
 static inline u64 tdp_mmu_clear_spte_bits(tdp_ptep_t sptep, u64 old_spte,
                                          u64 mask, int level)
 {
-       atomic64_t *sptep_atomic;
-
-       if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level)) {
-               sptep_atomic = (atomic64_t *)rcu_dereference(sptep);
-               return (u64)atomic64_fetch_and(~mask, sptep_atomic);
-       }
+       if (kvm_tdp_mmu_spte_need_atomic_write(old_spte, level))
+               return tdp_mmu_clear_spte_bits_atomic(sptep, mask);
 
        __kvm_tdp_mmu_write_spte(sptep, old_spte & ~mask);
        return old_spte;