linux-kernel - [PATCH 10/24] kvm: x86/mmu: Factor out handle disconnected pt

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Message-Id: <20210112181041.356734-11-bgardon@google.com>
Date:   Tue, 12 Jan 2021 10:10:27 -0800
From:   Ben Gardon <bgardon@...gle.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Peter Shier <pshier@...gle.com>,
        Peter Feiner <pfeiner@...gle.com>,
        Junaid Shahid <junaids@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        Yulei Zhang <yulei.kernel@...il.com>,
        Wanpeng Li <kernellwp@...il.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 10/24] kvm: x86/mmu: Factor out handle disconnected pt

Factor out the code to handle a disconnected subtree of the TDP paging
structure from the code to handle the change to an individual SPTE.
Future commits will build on this to allow asynchronous page freeing.

No functional change intended.

Reviewed-by: Peter Feiner <pfeiner@...gle.com>

Signed-off-by: Ben Gardon <bgardon@...gle.com>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 75 +++++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 29 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 55df596696c7..e8f35cd46b4c 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -234,6 +234,49 @@ static void handle_changed_spte_dirty_log(struct kvm *kvm, int as_id, gfn_t gfn,
 	}
 }
 
+/**
+ * handle_disconnected_tdp_mmu_page - handle a pt removed from the TDP structure
+ *
+ * @kvm: kvm instance
+ * @pt: the page removed from the paging structure
+ *
+ * Given a page table that has been removed from the TDP paging structure,
+ * iterates through the page table to clear SPTEs and free child page tables.
+ */
+static void handle_disconnected_tdp_mmu_page(struct kvm *kvm, u64 *pt)
+{
+	struct kvm_mmu_page *sp;
+	gfn_t gfn;
+	int level;
+	u64 old_child_spte;
+	int i;
+
+	sp = sptep_to_sp(pt);
+	gfn = sp->gfn;
+	level = sp->role.level;
+
+	trace_kvm_mmu_prepare_zap_page(sp);
+
+	list_del(&sp->link);
+
+	if (sp->lpage_disallowed)
+		unaccount_huge_nx_page(kvm, sp);
+
+	for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
+		old_child_spte = READ_ONCE(*(pt + i));
+		WRITE_ONCE(*(pt + i), 0);
+		handle_changed_spte(kvm, kvm_mmu_page_as_id(sp),
+			gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
+			old_child_spte, 0, level - 1);
+	}
+
+	kvm_flush_remote_tlbs_with_address(kvm, gfn,
+					   KVM_PAGES_PER_HPAGE(level));
+
+	free_page((unsigned long)pt);
+	kmem_cache_free(mmu_page_header_cache, sp);
+}
+
 /**
  * handle_changed_spte - handle bookkeeping associated with an SPTE change
  * @kvm: kvm instance
@@ -254,10 +297,6 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
 	bool was_leaf = was_present && is_last_spte(old_spte, level);
 	bool is_leaf = is_present && is_last_spte(new_spte, level);
 	bool pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
-	u64 *pt;
-	struct kvm_mmu_page *sp;
-	u64 old_child_spte;
-	int i;
 
 	WARN_ON(level > PT64_ROOT_MAX_LEVEL);
 	WARN_ON(level < PG_LEVEL_4K);
@@ -321,31 +360,9 @@ static void __handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
 	 * Recursively handle child PTs if the change removed a subtree from
 	 * the paging structure.
 	 */
-	if (was_present && !was_leaf && (pfn_changed || !is_present)) {
-		pt = spte_to_child_pt(old_spte, level);
-		sp = sptep_to_sp(pt);
-
-		trace_kvm_mmu_prepare_zap_page(sp);
-
-		list_del(&sp->link);
-
-		if (sp->lpage_disallowed)
-			unaccount_huge_nx_page(kvm, sp);
-
-		for (i = 0; i < PT64_ENT_PER_PAGE; i++) {
-			old_child_spte = READ_ONCE(*(pt + i));
-			WRITE_ONCE(*(pt + i), 0);
-			handle_changed_spte(kvm, as_id,
-				gfn + (i * KVM_PAGES_PER_HPAGE(level - 1)),
-				old_child_spte, 0, level - 1);
-		}
-
-		kvm_flush_remote_tlbs_with_address(kvm, gfn,
-						   KVM_PAGES_PER_HPAGE(level));
-
-		free_page((unsigned long)pt);
-		kmem_cache_free(mmu_page_header_cache, sp);
-	}
+	if (was_present && !was_leaf && (pfn_changed || !is_present))
+		handle_disconnected_tdp_mmu_page(kvm,
+				spte_to_child_pt(old_spte, level));
 }
 
 static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
-- 
2.30.0.284.gd98b1dd5eaa7-goog