A removed SPTE is never present, hence the "if" in kvm_tdp_mmu_map
only fails in the exact same conditions that the earlier loop
tested in order to issue a "break". So, instead of checking twice the
condition (upper level SPTEs could not be created or was frozen), just
exit the loop with a goto---the usual poor-man C replacement for RAII
early returns.
While at it, do not use the "ret" variable for return values of
functions that do not return a RET_PF_* enum. This is clearer
and also makes it possible to initialize ret to RET_PF_RETRY.
Suggested-by: Robert Hoo <robert.hu@xxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_mmu.c | 40 ++++++++++++++++++--------------------
1 file changed, 19 insertions(+), 21 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index e08596775427..771210ce5181 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1159,7 +1159,7 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
struct kvm *kvm = vcpu->kvm;
struct tdp_iter iter;
struct kvm_mmu_page *sp;
- int ret;
+ int ret = RET_PF_RETRY;
kvm_mmu_hugepage_adjust(vcpu, fault);
@@ -1168,23 +1168,25 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
rcu_read_lock();
tdp_mmu_for_each_pte(iter, mmu, fault->gfn, fault->gfn + 1) {
+ int r;
+
if (fault->nx_huge_page_workaround_enabled)
disallowed_hugepage_adjust(fault, iter.old_spte, iter.level);
if (iter.level == fault->goal_level)
break;
- /* Step down into the lower level page table if it exists. */
- if (is_shadow_present_pte(iter.old_spte) &&
- !is_large_pte(iter.old_spte))
- continue;
-
/*
* If SPTE has been frozen by another thread, just give up and
* retry, avoiding unnecessary page table allocation and free.
*/
if (is_removed_spte(iter.old_spte))
- break;
+ goto retry;
+
+ /* Step down into the lower level page table if it exists. */
+ if (is_shadow_present_pte(iter.old_spte) &&
+ !is_large_pte(iter.old_spte))
+ continue;
/*
* The SPTE is either non-present or points to a huge page that
@@ -1196,13 +1198,17 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
sp->nx_huge_page_disallowed = fault->huge_page_disallowed;
if (is_shadow_present_pte(iter.old_spte))
- ret = tdp_mmu_split_huge_page(kvm, &iter, sp, true);
+ r = tdp_mmu_split_huge_page(kvm, &iter, sp, true);
else
- ret = tdp_mmu_link_sp(kvm, &iter, sp, true);
+ r = tdp_mmu_link_sp(kvm, &iter, sp, true);
- if (ret) {
+ /*
+ * Also force the guest to retry the access if the upper level SPTEs
+ * aren't in place.
+ */
+ if (r) {
tdp_mmu_free_sp(sp);
- break;
+ goto retry;
}
if (fault->huge_page_disallowed &&
@@ -1213,18 +1219,10 @@ int kvm_tdp_mmu_map(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault)
}
}
- /*
- * Force the guest to retry the access if the upper level SPTEs aren't
- * in place, or if the target leaf SPTE is frozen by another CPU.
- */
- if (iter.level != fault->goal_level || is_removed_spte(iter.old_spte)) {
- rcu_read_unlock();
- return RET_PF_RETRY;
- }
-
ret = tdp_mmu_map_handle_target_level(vcpu, fault, &iter);
- rcu_read_unlock();
+retry:
+ rcu_read_unlock();
return ret;
}
--
2.31.1
