KVM: PPC: Book3S HV: Unify dirty page map between HPT and radix

Currently, the HPT code in HV KVM maintains a dirty bit per guest page
in the rmap array, whether or not dirty page tracking has been enabled
for the memory slot.  In contrast, the radix code maintains a dirty
bit per guest page in memslot->dirty_bitmap, and only does so when
dirty page tracking has been enabled.

This changes the HPT code to maintain the dirty bits in the memslot
dirty_bitmap like radix does.  This results in slightly less code
overall, and will mean that we do not lose the dirty bits when
transitioning between HPT and radix mode in future.

There is one minor change to behaviour as a result.  With HPT, when
dirty tracking was enabled for a memslot, we would previously clear
all the dirty bits at that point (both in the HPT entries and in the
rmap arrays), meaning that a KVM_GET_DIRTY_LOG ioctl immediately
following would show no pages as dirty (assuming no vcpus have run
in the meantime).  With this change, the dirty bits on HPT entries
are not cleared at the point where dirty tracking is enabled, so
KVM_GET_DIRTY_LOG would show as dirty any guest pages that are
resident in the HPT and dirty.  This is consistent with what happens
on radix.

This also fixes a bug in the mark_pages_dirty() function for radix
(in the sense that the function no longer exists).  In the case where
a large page of 64 normal pages or more is marked dirty, the
addressing of the dirty bitmap was incorrect and could write past
the end of the bitmap.  Fortunately this case was never hit in
practice because a 2MB large page is only 32 x 64kB pages, and we
don't support backing the guest with 1GB huge pages at this point.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

1 files changed, 37 insertions, 23 deletions

diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index cf98f17c1aa6..26c11f678fbf 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -107,23 +107,39 @@ void kvmppc_add_revmap_chain(struct kvm *kvm, struct revmap_entry *rev,
 }
 EXPORT_SYMBOL_GPL(kvmppc_add_revmap_chain);
 
-/* Update the changed page order field of an rmap entry */
-void kvmppc_update_rmap_change(unsigned long *rmap, unsigned long psize)
+/* Update the dirty bitmap of a memslot */
+void kvmppc_update_dirty_map(struct kvm_memory_slot *memslot,
+			     unsigned long gfn, unsigned long psize)
 {
-	unsigned long order;
+	unsigned long npages;
 
-	if (!psize)
+	if (!psize || !memslot->dirty_bitmap)
 		return;
-	order = ilog2(psize);
-	order <<= KVMPPC_RMAP_CHG_SHIFT;
-	if (order > (*rmap & KVMPPC_RMAP_CHG_ORDER))
-		*rmap = (*rmap & ~KVMPPC_RMAP_CHG_ORDER) | order;
+	npages = (psize + PAGE_SIZE - 1) / PAGE_SIZE;
+	gfn -= memslot->base_gfn;
+	set_dirty_bits_atomic(memslot->dirty_bitmap, gfn, npages);
+}
+EXPORT_SYMBOL_GPL(kvmppc_update_dirty_map);
+
+static void kvmppc_set_dirty_from_hpte(struct kvm *kvm,
+				unsigned long hpte_v, unsigned long hpte_gr)
+{
+	struct kvm_memory_slot *memslot;
+	unsigned long gfn;
+	unsigned long psize;
+
+	psize = kvmppc_actual_pgsz(hpte_v, hpte_gr);
+	gfn = hpte_rpn(hpte_gr, psize);
+	memslot = __gfn_to_memslot(kvm_memslots_raw(kvm), gfn);
+	if (memslot && memslot->dirty_bitmap)
+		kvmppc_update_dirty_map(memslot, gfn, psize);
 }
-EXPORT_SYMBOL_GPL(kvmppc_update_rmap_change);
 
 /* Returns a pointer to the revmap entry for the page mapped by a HPTE */
 static unsigned long *revmap_for_hpte(struct kvm *kvm, unsigned long hpte_v,
-				      unsigned long hpte_gr)
+				      unsigned long hpte_gr,
+				      struct kvm_memory_slot **memslotp,
+				      unsigned long *gfnp)
 {
 	struct kvm_memory_slot *memslot;
 	unsigned long *rmap;
@@ -131,6 +147,10 @@ static unsigned long *revmap_for_hpte(struct kvm *kvm, unsigned long hpte_v,
 
 	gfn = hpte_rpn(hpte_gr, kvmppc_actual_pgsz(hpte_v, hpte_gr));
 	memslot = __gfn_to_memslot(kvm_memslots_raw(kvm), gfn);
+	if (memslotp)
+		*memslotp = memslot;
+	if (gfnp)
+		*gfnp = gfn;
 	if (!memslot)
 		return NULL;
 
@@ -147,10 +167,12 @@ static void remove_revmap_chain(struct kvm *kvm, long pte_index,
 	unsigned long ptel, head;
 	unsigned long *rmap;
 	unsigned long rcbits;
+	struct kvm_memory_slot *memslot;
+	unsigned long gfn;
 
 	rcbits = hpte_r & (HPTE_R_R | HPTE_R_C);
 	ptel = rev->guest_rpte |= rcbits;
-	rmap = revmap_for_hpte(kvm, hpte_v, ptel);
+	rmap = revmap_for_hpte(kvm, hpte_v, ptel, &memslot, &gfn);
 	if (!rmap)
 		return;
 	lock_rmap(rmap);
@@ -169,8 +191,8 @@ static void remove_revmap_chain(struct kvm *kvm, long pte_index,
 	}
 	*rmap |= rcbits << KVMPPC_RMAP_RC_SHIFT;
 	if (rcbits & HPTE_R_C)
-		kvmppc_update_rmap_change(rmap,
-					  kvmppc_actual_pgsz(hpte_v, hpte_r));
+		kvmppc_update_dirty_map(memslot, gfn,
+					kvmppc_actual_pgsz(hpte_v, hpte_r));
 	unlock_rmap(rmap);
 }
 
@@ -798,7 +820,7 @@ long kvmppc_h_clear_ref(struct kvm_vcpu *vcpu, unsigned long flags,
 		gr |= r & (HPTE_R_R | HPTE_R_C);
 		if (r & HPTE_R_R) {
 			kvmppc_clear_ref_hpte(kvm, hpte, pte_index);
-			rmap = revmap_for_hpte(kvm, v, gr);
+			rmap = revmap_for_hpte(kvm, v, gr, NULL, NULL);
 			if (rmap) {
 				lock_rmap(rmap);
 				*rmap |= KVMPPC_RMAP_REFERENCED;
@@ -820,7 +842,6 @@ long kvmppc_h_clear_mod(struct kvm_vcpu *vcpu, unsigned long flags,
 	__be64 *hpte;
 	unsigned long v, r, gr;
 	struct revmap_entry *rev;
-	unsigned long *rmap;
 	long ret = H_NOT_FOUND;
 
 	if (kvm_is_radix(kvm))
@@ -849,16 +870,9 @@ long kvmppc_h_clear_mod(struct kvm_vcpu *vcpu, unsigned long flags,
 		r = be64_to_cpu(hpte[1]);
 		gr |= r & (HPTE_R_R | HPTE_R_C);
 		if (r & HPTE_R_C) {
-			unsigned long psize = kvmppc_actual_pgsz(v, r);
 			hpte[1] = cpu_to_be64(r & ~HPTE_R_C);
 			eieio();
-			rmap = revmap_for_hpte(kvm, v, gr);
-			if (rmap) {
-				lock_rmap(rmap);
-				*rmap |= KVMPPC_RMAP_CHANGED;
-				kvmppc_update_rmap_change(rmap, psize);
-				unlock_rmap(rmap);
-			}
+			kvmppc_set_dirty_from_hpte(kvm, v, gr);
 		}
 	}
 	vcpu->arch.gpr[4] = gr;