[PATCH 16/22] kvm: mmu: Add dirty logging handler for changed sptes

[Ben Gardon]

Add a function to handle the dirty logging bookkeeping associated with
SPTE changes. This will be important for future commits which will allow
the TDP MMU to log dirty pages the same way the x86 shadow paging based
MMU does.

Tested by running kvm-unit-tests and KVM selftests on an Intel Haswell
machine. This series introduced no new failures.

This series can be viewed in Gerrit at:
	https://linux-review.googlesource.com/c/virt/kvm/kvm/+/2538

Signed-off-by: Ben Gardon <bgardon@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 21 +++++++++++++++++++++
 include/linux/kvm_host.h   |  1 +
 virt/kvm/kvm_main.c        |  6 ++----
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 3119583409131..bbe973d3f8084 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -236,6 +236,24 @@ static void handle_changed_spte_acc_track(u64 old_spte, u64 new_spte, int level)
 		kvm_set_pfn_accessed(spte_to_pfn(old_spte));
 }
 
+static void handle_changed_spte_dlog(struct kvm *kvm, int as_id, gfn_t gfn,
+				    u64 old_spte, u64 new_spte, int level)
+{
+	bool pfn_changed;
+	struct kvm_memory_slot *slot;
+
+	if (level > PG_LEVEL_4K)
+		return;
+
+	pfn_changed = spte_to_pfn(old_spte) != spte_to_pfn(new_spte);
+
+	if ((!is_writable_pte(old_spte) || pfn_changed) &&
+	    is_writable_pte(new_spte)) {
+		slot = __gfn_to_memslot(__kvm_memslots(kvm, as_id), gfn);
+		mark_page_dirty_in_slot(slot, gfn);
+	}
+}
+
 /**
  * handle_changed_spte - handle bookkeeping associated with an SPTE change
  * @kvm: kvm instance
@@ -348,6 +366,7 @@ static void handle_changed_spte(struct kvm *kvm, int as_id, gfn_t gfn,
 {
 	__handle_changed_spte(kvm, as_id, gfn, old_spte, new_spte, level);
 	handle_changed_spte_acc_track(old_spte, new_spte, level);
+	handle_changed_spte_dlog(kvm, as_id, gfn, old_spte, new_spte, level);
 }
 
 #define for_each_tdp_pte_root(_iter, _root, _start, _end) \
@@ -685,6 +704,8 @@ static int age_gfn_range(struct kvm *kvm, struct kvm_memory_slot *slot,
 		*iter.sptep = new_spte;
 		__handle_changed_spte(kvm, as_id, iter.gfn, iter.old_spte,
 				      new_spte, iter.level);
+		handle_changed_spte_dlog(kvm, as_id, iter.gfn, iter.old_spte,
+					 new_spte, iter.level);
 		young = true;
 	}
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index a460bc712a81c..2f8c3f644d809 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -798,6 +798,7 @@ struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
 bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn);
 bool kvm_vcpu_is_visible_gfn(struct kvm_vcpu *vcpu, gfn_t gfn);
 unsigned long kvm_host_page_size(struct kvm_vcpu *vcpu, gfn_t gfn);
+void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot, gfn_t gfn);
 void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
 
 struct kvm_memslots *kvm_vcpu_memslots(struct kvm_vcpu *vcpu);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f9c80351c9efd..b5082ce60a33f 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -143,8 +143,6 @@ static void hardware_disable_all(void);
 
 static void kvm_io_bus_destroy(struct kvm_io_bus *bus);
 
-static void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot, gfn_t gfn);
-
 __visible bool kvm_rebooting;
 EXPORT_SYMBOL_GPL(kvm_rebooting);
 
@@ -2640,8 +2638,7 @@ int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len)
 }
 EXPORT_SYMBOL_GPL(kvm_clear_guest);
 
-static void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot,
-				    gfn_t gfn)
+void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot, gfn_t gfn)
 {
 	if (memslot && memslot->dirty_bitmap) {
 		unsigned long rel_gfn = gfn - memslot->base_gfn;
@@ -2649,6 +2646,7 @@ static void mark_page_dirty_in_slot(struct kvm_memory_slot *memslot,
 		set_bit_le(rel_gfn, memslot->dirty_bitmap);
 	}
 }
+EXPORT_SYMBOL_GPL(mark_page_dirty_in_slot);
 
 void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
 {
-- 
2.28.0.709.gb0816b6eb0-goog