KVM: PPC: Book3S HV: Add KVM stat largepages_[2M/1G]

This adds an entry to the kvm_stats_debugfs directory which provides the
number of large (2M or 1G) pages which have been used to setup the guest
mappings, for radix guests.
Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@gmail.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

arch/powerpc/include/asm/kvm_host.h

@@ -99,6 +99,8 @@ struct kvm_nested_guest;
 
 struct kvm_vm_stat {
 	ulong remote_tlb_flush;
+	ulong num_2M_pages;
+	ulong num_1G_pages;
 };
 
 struct kvm_vcpu_stat {

arch/powerpc/kvm/book3s.c

@@ -39,6 +39,7 @@
 #include "book3s.h"
 #include "trace.h"
 
+#define VM_STAT(x) offsetof(struct kvm, stat.x), KVM_STAT_VM
 #define VCPU_STAT(x) offsetof(struct kvm_vcpu, stat.x), KVM_STAT_VCPU
 
 /* #define EXIT_DEBUG */
@@ -71,6 +72,8 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	{ "pthru_all",       VCPU_STAT(pthru_all) },
 	{ "pthru_host",      VCPU_STAT(pthru_host) },
 	{ "pthru_bad_aff",   VCPU_STAT(pthru_bad_aff) },
+	{ "largepages_2M",    VM_STAT(num_2M_pages) },
+	{ "largepages_1G",    VM_STAT(num_1G_pages) },
 	{ NULL }
 };
 

arch/powerpc/kvm/book3s_64_mmu_radix.c

@@ -403,8 +403,13 @@ void kvmppc_unmap_pte(struct kvm *kvm, pte_t *pte, unsigned long gpa,
 		if (!memslot)
 			return;
 	}
-	if (shift)
+	if (shift) { /* 1GB or 2MB page */
 		page_size = 1ul << shift;
+		if (shift == PMD_SHIFT)
+			kvm->stat.num_2M_pages--;
+		else if (shift == PUD_SHIFT)
+			kvm->stat.num_1G_pages--;
+	}
 
 	gpa &= ~(page_size - 1);
 	hpa = old & PTE_RPN_MASK;
@@ -878,6 +883,14 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 		put_page(page);
 	}
 
+	/* Increment number of large pages if we (successfully) inserted one */
+	if (!ret) {
+		if (level == 1)
+			kvm->stat.num_2M_pages++;
+		else if (level == 2)
+			kvm->stat.num_1G_pages++;
+	}
+
 	return ret;
 }