[PATCH v9 67/84] KVM: introspection: add KVMI_VM_GET_MAX_GFN

[Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>]

From: Ștefan Șicleru <ssicleru@xxxxxxxxxxxxxxx>

The introspection tool will use this command to get the memory address
range for which it can set access restrictions.

Signed-off-by: Ștefan Șicleru <ssicleru@xxxxxxxxxxxxxxx>
Co-developed-by: Nicușor Cîțu <ncitu@xxxxxxxxxxxxxxx>
Signed-off-by: Nicușor Cîțu <ncitu@xxxxxxxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
 Documentation/virt/kvm/kvmi.rst               | 19 +++++++++++++++++++
 include/uapi/linux/kvmi.h                     |  6 ++++++
 .../testing/selftests/kvm/x86_64/kvmi_test.c  | 12 ++++++++++++
 virt/kvm/introspection/kvmi_msg.c             | 13 +++++++++++++
 4 files changed, 50 insertions(+)

diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index 4263a9ac90e4..7da8efd18b89 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -789,6 +789,25 @@ exception.
 * -KVM_EBUSY - another *KVMI_VCPU_INJECT_EXCEPTION*-*KVMI_EVENT_TRAP* pair
                is in progress
 
+17. KVMI_VM_GET_MAX_GFN
+-----------------------
+
+:Architecture: all
+:Versions: >= 1
+:Parameters: none
+:Returns:
+
+::
+
+        struct kvmi_error_code;
+        struct kvmi_vm_get_max_gfn_reply {
+                __u64 gfn;
+        };
+
+Provides the maximum GFN allocated to the VM by walking through all
+memory slots allocated by KVM. Stricly speaking, the returned value refers
+to the first inaccessible GFN, next to the maximum accessible GFN.
+
 Events
 ======
 
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index faf4624d7a97..2a4cc8c41465 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -37,6 +37,8 @@ enum {
 	KVMI_VCPU_CONTROL_CR       = 15,
 	KVMI_VCPU_INJECT_EXCEPTION = 16,
 
+	KVMI_VM_GET_MAX_GFN = 17,
+
 	KVMI_NUM_MESSAGES
 };
 
@@ -149,6 +151,10 @@ struct kvmi_vm_control_cleanup {
 	__u32 padding3;
 };
 
+struct kvmi_vm_get_max_gfn_reply {
+	__u64 gfn;
+};
+
 struct kvmi_event {
 	__u16 size;
 	__u16 vcpu;
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index 9abf4ec0d09a..105adf75a68d 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -1420,6 +1420,17 @@ static void test_cmd_vcpu_inject_exception(struct kvm_vm *vm)
 	disable_vcpu_event(vm, KVMI_EVENT_BREAKPOINT);
 }
 
+static void test_cmd_vm_get_max_gfn(void)
+{
+	struct kvmi_vm_get_max_gfn_reply rpl;
+	struct kvmi_msg_hdr req;
+
+	test_vm_command(KVMI_VM_GET_MAX_GFN, &req, sizeof(req),
+			&rpl, sizeof(rpl));
+
+	pr_info("max_gfn: 0x%llx\n", rpl.gfn);
+}
+
 static void test_introspection(struct kvm_vm *vm)
 {
 	srandom(time(0));
@@ -1445,6 +1456,7 @@ static void test_introspection(struct kvm_vm *vm)
 	test_cmd_vm_control_cleanup(vm);
 	test_cmd_vcpu_control_cr(vm);
 	test_cmd_vcpu_inject_exception(vm);
+	test_cmd_vm_get_max_gfn();
 
 	unhook_introspection(vm);
 }
diff --git a/virt/kvm/introspection/kvmi_msg.c b/virt/kvm/introspection/kvmi_msg.c
index 63efb85ff1ae..18bc1a711845 100644
--- a/virt/kvm/introspection/kvmi_msg.c
+++ b/virt/kvm/introspection/kvmi_msg.c
@@ -322,6 +322,18 @@ static int handle_vm_control_cleanup(struct kvm_introspection *kvmi,
 	return kvmi_msg_vm_reply(kvmi, msg, ec, NULL, 0);
 }
 
+static int handle_vm_get_max_gfn(struct kvm_introspection *kvmi,
+				 const struct kvmi_msg_hdr *msg,
+				 const void *req)
+{
+	struct kvmi_vm_get_max_gfn_reply rpl;
+
+	memset(&rpl, 0, sizeof(rpl));
+	rpl.gfn = kvm_get_max_gfn(kvmi->kvm);
+
+	return kvmi_msg_vm_reply(kvmi, msg, 0, &rpl, sizeof(rpl));
+}
+
 /*
  * These commands are executed by the receiving thread.
  */
@@ -334,6 +346,7 @@ static int(*const msg_vm[])(struct kvm_introspection *,
 	[KVMI_VM_CONTROL_CLEANUP] = handle_vm_control_cleanup,
 	[KVMI_VM_CONTROL_EVENTS]  = handle_vm_control_events,
 	[KVMI_VM_GET_INFO]        = handle_vm_get_info,
+	[KVMI_VM_GET_MAX_GFN]     = handle_vm_get_max_gfn,
 	[KVMI_VM_READ_PHYSICAL]   = handle_vm_read_physical,
 	[KVMI_VM_WRITE_PHYSICAL]  = handle_vm_write_physical,
 };