kvm: Dump page tables at exit

To make debugging more easy, dump page tables at exit as suggested by Avi
Kivity.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

include/kvm/kvm.h

@@ -45,6 +45,7 @@ bool kvm__emulate_io(struct kvm *self, uint16_t port, void *data, int direction,
  */
 void kvm__show_code(struct kvm *self);
 void kvm__show_registers(struct kvm *self);
+void kvm__show_page_tables(struct kvm *self);
 void kvm__dump_mem(struct kvm *self, unsigned long addr, unsigned long size);
 
 extern const char *kvm_exit_reasons[];

kvm.c

@@ -351,6 +351,11 @@ static inline uint64_t ip_flat_to_real(struct kvm *self, uint64_t ip)
 	return ip - (cs << 4);
 }
 
+static inline bool is_in_protected_mode(struct kvm *self)
+{
+	return self->sregs.cr0 & 0x01;
+}
+
 static inline uint64_t ip_to_flat(struct kvm *self, uint64_t ip)
 {
 	uint64_t cs;
@@ -359,7 +364,7 @@ static inline uint64_t ip_to_flat(struct kvm *self, uint64_t ip)
 	 * NOTE! We should take code segment base address into account here.
 	 * Luckily it's usually zero because Linux uses flat memory model.
 	 */
-	if (self->sregs.cr0 & 0x01)
+	if (is_in_protected_mode(self))
 		return ip;
 
 	cs = self->sregs.cs.selector;
@@ -659,6 +664,31 @@ void kvm__show_code(struct kvm *self)
 	kvm__dump_mem(self, self->regs.rsp, 32);
 }
 
+void kvm__show_page_tables(struct kvm *self)
+{
+	uint64_t *pte1;
+	uint64_t *pte2;
+	uint64_t *pte3;
+	uint64_t *pte4;
+
+	if (!is_in_protected_mode(self))
+		return;
+
+	if (ioctl(self->vcpu_fd, KVM_GET_SREGS, &self->sregs) < 0)
+		die("KVM_GET_SREGS failed");
+
+	pte4	= guest_flat_to_host(self, self->sregs.cr3);
+	pte3	= guest_flat_to_host(self, (*pte4 & ~0xfff));
+	pte2	= guest_flat_to_host(self, (*pte3 & ~0xfff));
+	pte1	= guest_flat_to_host(self, (*pte2 & ~0xfff));
+
+	printf("Page Tables:\n");
+	if (*pte2 & (1 << 7))
+		printf(" pte4: %016lx   pte3: %016lx   pte2: %016lx\n", *pte4, *pte3, *pte2);
+	else
+		printf(" pte4: %016lx   pte3: %016lx   pte2: %016lx   pte1: %016lx\n", *pte4, *pte3, *pte2, *pte1);
+}
+
 void kvm__dump_mem(struct kvm *self, unsigned long addr, unsigned long size)
 {
 	unsigned char *p;

main.c

@@ -91,6 +91,7 @@ exit_kvm:
 
 	kvm__show_registers(kvm);
 	kvm__show_code(kvm);
+	kvm__show_page_tables(kvm);
 
 	kvm__delete(kvm);