Not stepping down in TDP iterator in `zap_all` case avoids re-reading the
non-leaf SPTEs, thus accelerates the zapping process . But when the number
of SPTEs is too large, we may run out of CPU time and causes a RCU stall
warnings in __handle_changed_pte() in the context of zap_gfn_range().
Revert this patch to allow eliminating RCU stall warning using a two-phase
zapping for `zap_all` case.
This reverts commit 0103098fb4f13b447b26ed514bcd3140f6791047.
Cc: Sean Christopherson <seanjc@xxxxxxxxxx>
Cc: Ben Gardon <bgardon@xxxxxxxxxx>
Cc: David Matlack <dmatlack@xxxxxxxxxx>
Signed-off-by: Mingwei Zhang <mizhang@xxxxxxxxxx>
---
arch/x86/kvm/mmu/tdp_mmu.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 7c5dd83e52de..89d16bb104de 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -706,12 +706,6 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
bool zap_all = (start == 0 && end >= max_gfn_host);
struct tdp_iter iter;
- /*
- * No need to try to step down in the iterator when zapping all SPTEs,
- * zapping the top-level non-leaf SPTEs will recurse on their children.
- */
- int min_level = zap_all ? root->role.level : PG_LEVEL_4K;
-
/*
* Bound the walk at host.MAXPHYADDR, guest accesses beyond that will
* hit a #PF(RSVD) and never get to an EPT Violation/Misconfig / #NPF,
@@ -723,8 +717,7 @@ static bool zap_gfn_range(struct kvm *kvm, struct kvm_mmu_page *root,
rcu_read_lock();
- for_each_tdp_pte_min_level(iter, root->spt, root->role.level,
- min_level, start, end) {
+ tdp_root_for_each_pte(iter, root, start, end) {
retry:
if (can_yield &&
tdp_mmu_iter_cond_resched(kvm, &iter, flush, shared)) {
--
2.34.0.rc2.393.gf8c9666880-goog
