diff options
| author | Uros Bizjak <ubizjak@gmail.com> | 2022-05-18 15:51:11 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-06-15 08:11:14 -0400 |
| commit | aee98a6838d52d5cca14610d228893e9208f4ed1 (patch) | |
| tree | 79551e55c29d47e91ef351508b21ab314744ce1b /arch/x86/kvm | |
| parent | d895f28ed6da96d7b922bd79977e2b732b103a99 (diff) | |
KVM: x86/mmu: Use try_cmpxchg64 in tdp_mmu_set_spte_atomic
Use try_cmpxchg64 instead of cmpxchg64 (*ptr, old, new) != old in
tdp_mmu_set_spte_atomic. cmpxchg returns success in ZF flag, so this
change saves a compare after cmpxchg (and related move instruction
in front of cmpxchg). Also, remove explicit assignment to iter->old_spte
when cmpxchg fails, this is what try_cmpxchg does implicitly.
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Message-Id: <20220518135111.3535-1-ubizjak@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
| -rw-r--r-- | arch/x86/kvm/mmu/tdp_mmu.c | 12 |
1 files changed, 1 insertions, 11 deletions
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c index 7b9265d67131..2cd060eb34a4 100644 --- a/arch/x86/kvm/mmu/tdp_mmu.c +++ b/arch/x86/kvm/mmu/tdp_mmu.c @@ -633,7 +633,6 @@ static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm, u64 new_spte) { u64 *sptep = rcu_dereference(iter->sptep); - u64 old_spte; /* * The caller is responsible for ensuring the old SPTE is not a REMOVED @@ -649,17 +648,8 @@ static inline int tdp_mmu_set_spte_atomic(struct kvm *kvm, * Note, fast_pf_fix_direct_spte() can also modify TDP MMU SPTEs and * does not hold the mmu_lock. */ - old_spte = cmpxchg64(sptep, iter->old_spte, new_spte); - if (old_spte != iter->old_spte) { - /* - * The page table entry was modified by a different logical - * CPU. Refresh iter->old_spte with the current value so the - * caller operates on fresh data, e.g. if it retries - * tdp_mmu_set_spte_atomic(). - */ - iter->old_spte = old_spte; + if (!try_cmpxchg64(sptep, &iter->old_spte, new_spte)) return -EBUSY; - } __handle_changed_spte(kvm, iter->as_id, iter->gfn, iter->old_spte, new_spte, iter->level, true); |