[PATCH] KVM: x86: use again the flush argument of __link_shadow_page()

[Paolo Bonzini]

Except in the case of parentless nested-TDP pages, mmu_page_zap_pte()
clears the SPTE but leaves the invalid_list empty.  In this case, using
kvm_flush_remote_tlbs() as kvm_mmu_remote_flush_or_zap() does is overkill.
Avoid flushing the entirety of the remote TLBs unless the invalid_list
was populated: instead, use a more efficient gfn-targeting flush (if
available) and skip it altogether if the caller guarantees that a TLB
flush is not necessary.

Based-on: <20260503201029.106481-1-pbonzini@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/mmu.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 892246204435..85bec8eeace8 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -2541,8 +2541,10 @@ static void __link_shadow_page(struct kvm *kvm,
 		parent_sp = sptep_to_sp(sptep);
 		WARN_ON_ONCE(parent_sp->role.level == PG_LEVEL_4K);
 
-		mmu_page_zap_pte(kvm, parent_sp, sptep, &invalid_list);
-		kvm_mmu_remote_flush_or_zap(kvm, &invalid_list, true);
+		if (mmu_page_zap_pte(kvm, parent_sp, sptep, &invalid_list))
+			kvm_mmu_commit_zap_page(kvm, &invalid_list);
+		else if (flush)
+			kvm_flush_remote_tlbs_sptep(kvm, sptep);
 	}
 
 	spte = make_nonleaf_spte(sp->spt, sp_ad_disabled(sp));
-- 
2.54.0