KVM: LoongArch: Mark "struct page" pfns accessed only in "slow" page fault path

Mark pages accessed only in the slow path, before dropping mmu_lock when
faulting in guest memory so that LoongArch can convert to
kvm_release_faultin_page() without tripping its lockdep assertion on
mmu_lock being held.

Reviewed-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-67-seanjc@google.com>

Author: sean-jc

arch/loongarch/kvm/mmu.c

@@ -552,12 +552,10 @@ bool kvm_test_age_gfn(struct kvm *kvm, struct kvm_gfn_range *range)
 static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool write)
 {
 	int ret = 0;
-	kvm_pfn_t pfn = 0;
 	kvm_pte_t *ptep, changed, new;
 	gfn_t gfn = gpa >> PAGE_SHIFT;
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_memory_slot *slot;
-	struct page *page;
 
 	spin_lock(&kvm->mmu_lock);
 
@@ -570,8 +568,6 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
 
 	/* Track access to pages marked old */
 	new = kvm_pte_mkyoung(*ptep);
-	/* call kvm_set_pfn_accessed() after unlock */
-
 	if (write && !kvm_pte_dirty(new)) {
 		if (!kvm_pte_write(new)) {
 			ret = -EFAULT;
@@ -595,22 +591,10 @@ static int kvm_map_page_fast(struct kvm_vcpu *vcpu, unsigned long gpa, bool writ
 	}
 
 	changed = new ^ (*ptep);
-	if (changed) {
+	if (changed)
 		kvm_set_pte(ptep, new);
-		pfn = kvm_pte_pfn(new);
-		page = kvm_pfn_to_refcounted_page(pfn);
-		if (page)
-			get_page(page);
-	}
-	spin_unlock(&kvm->mmu_lock);
 
-	if (changed) {
-		if (kvm_pte_young(changed))
-			kvm_set_pfn_accessed(pfn);
-
-		if (page)
-			put_page(page);
-	}
+	spin_unlock(&kvm->mmu_lock);
 
 	if (kvm_pte_dirty(changed))
 		mark_page_dirty(kvm, gfn);