[PATCH v12 75/77] KVM: introspection: add KVMI_VCPU_TRANSLATE_GVA

Adalbert Lazăr
2021-10-06T17:31:11Z

This helps the introspection tool with the GVA to GPA translations
without the need to read or monitor the guest page tables.

Signed-off-by: Adalbert Laz?r <alazar at bitdefender.com>
---
 Documentation/virt/kvm/kvmi.rst               | 32 +++++++++++++++++++
 arch/x86/kvm/kvmi_msg.c                       | 15 +++++++++
 include/uapi/linux/kvmi.h                     |  9 ++++++
 .../testing/selftests/kvm/x86_64/kvmi_test.c  | 30 +++++++++++++++++
 4 files changed, 86 insertions(+)

diff --git a/Documentation/virt/kvm/kvmi.rst b/Documentation/virt/kvm/kvmi.rst
index 84922d327255..17735d099be2 100644
--- a/Documentation/virt/kvm/kvmi.rst
+++ b/Documentation/virt/kvm/kvmi.rst
@@ -1055,6 +1055,38 @@ to the introspection tool.
 * -KVM_EINVAL - the padding is not zero
 * -KVM_EAGAIN - the selected vCPU can't be introspected yet

+24. KVMI_VCPU_TRANSLATE_GVA
+---------------------------
+
+:Architectures: x86
+:Versions: >= 1
+:Parameters:
+
+::
+
+	struct kvmi_vcpu_hdr;
+	struct kvmi_vcpu_translate_gva {
+		__u64 gva;
+	};
+
+:Returns:
+
+::
+
+	struct kvmi_error_code;
+	struct kvmi_vcpu_translate_gva_reply {
+		__u64 gpa;
+	};
+
+Translates a guest virtual address (``gva``) to a guest physical address
+(``gpa``) or ~0 if the address cannot be translated.
+
+:Errors:
+
+* -KVM_EINVAL - the selected vCPU is invalid
+* -KVM_EINVAL - the padding is not zero
+* -KVM_EAGAIN - the selected vCPU can't be introspected yet
+
 Events
 =====
diff --git a/arch/x86/kvm/kvmi_msg.c b/arch/x86/kvm/kvmi_msg.c
index ea38eb7ccb7c..cdd497a342a0 100644
--- a/arch/x86/kvm/kvmi_msg.c
+++ b/arch/x86/kvm/kvmi_msg.c
@@ -312,6 +312,20 @@ static int handle_vcpu_control_singlestep(const struct
kvmi_vcpu_msg_job *job,
 	return kvmi_msg_vcpu_reply(job, msg, ec, NULL, 0);
 }

+static int handle_vcpu_translate_gva(const struct kvmi_vcpu_msg_job *job,
+				     const struct kvmi_msg_hdr *msg,
+				     const void *_req)
+{
+	const struct kvmi_vcpu_translate_gva *req = _req;
+	struct kvmi_vcpu_translate_gva_reply rpl;
+
+	memset(&rpl, 0, sizeof(rpl));
+
+	rpl.gpa = kvm_mmu_gva_to_gpa_system(job->vcpu, req->gva, 0, NULL);
+
+	return kvmi_msg_vcpu_reply(job, msg, 0, &rpl, sizeof(rpl));
+}
+
 static const kvmi_vcpu_msg_job_fct msg_vcpu[] = {
 	[KVMI_VCPU_CONTROL_CR]         = handle_vcpu_control_cr,
 	[KVMI_VCPU_CONTROL_MSR]        = handle_vcpu_control_msr,
@@ -325,6 +339,7 @@ static const kvmi_vcpu_msg_job_fct msg_vcpu[] = {
 	[KVMI_VCPU_INJECT_EXCEPTION]   = handle_vcpu_inject_exception,
 	[KVMI_VCPU_SET_REGISTERS]      = handle_vcpu_set_registers,
 	[KVMI_VCPU_SET_XSAVE]          = handle_vcpu_set_xsave,
+	[KVMI_VCPU_TRANSLATE_GVA]      = handle_vcpu_translate_gva,
 };

 kvmi_vcpu_msg_job_fct kvmi_arch_vcpu_msg_handler(u16 id)
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index 148d145ddea0..a1bfa845fed8 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -50,6 +50,7 @@ enum {
 	KVMI_VCPU_GET_MTRR_TYPE      = KVMI_VCPU_MESSAGE_ID(11),
 	KVMI_VCPU_CONTROL_MSR        = KVMI_VCPU_MESSAGE_ID(12),
 	KVMI_VCPU_CONTROL_SINGLESTEP = KVMI_VCPU_MESSAGE_ID(13),
+	KVMI_VCPU_TRANSLATE_GVA      = KVMI_VCPU_MESSAGE_ID(14),

 	KVMI_NEXT_VCPU_MESSAGE
 };
@@ -228,4 +229,12 @@ struct kvmi_vcpu_event_singlestep {
 	__u8 padding[7];
 };

+struct kvmi_vcpu_translate_gva {
+	__u64 gva;
+};
+
+struct kvmi_vcpu_translate_gva_reply {
+	__u64 gpa;
+};
+
 #endif /* _UAPI__LINUX_KVMI_H */
diff --git a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
index faef908eeedd..fc59a8b9f99a 100644
--- a/tools/testing/selftests/kvm/x86_64/kvmi_test.c
+++ b/tools/testing/selftests/kvm/x86_64/kvmi_test.c
@@ -1894,6 +1894,35 @@ static void test_cmd_vcpu_control_singlestep(struct
kvm_vm *vm)
 		test_unsupported_singlestep(vm);
 }

+static void cmd_translate_gva(struct kvm_vm *vm, vm_vaddr_t gva,
+			      vm_paddr_t expected_gpa)
+{
+	struct {
+		struct kvmi_msg_hdr hdr;
+		struct kvmi_vcpu_hdr vcpu_hdr;
+		struct kvmi_vcpu_translate_gva cmd;
+	} req = { 0 };
+	struct kvmi_vcpu_translate_gva_reply rpl;
+
+	req.cmd.gva = gva;
+
+	test_vcpu0_command(vm, KVMI_VCPU_TRANSLATE_GVA, &req.hdr, sizeof(req),
+			  &rpl, sizeof(rpl), 0);
+	TEST_ASSERT(rpl.gpa == expected_gpa,
+		    "Translation failed for gva 0x%lx -> gpa 0x%llx instead of
0x%lx\n",
+		    gva, rpl.gpa, expected_gpa);
+}
+
+static void test_cmd_translate_gva(struct kvm_vm *vm)
+{
+	cmd_translate_gva(vm, test_gva, test_gpa);
+	pr_debug("Tested gva 0x%lx to gpa 0x%lx\n", test_gva, test_gpa);
+
+	cmd_translate_gva(vm, -1, ~0);
+	pr_debug("Tested gva 0x%lx to gpa 0x%lx\n",
+		 (vm_vaddr_t)-1, (vm_paddr_t)-1);
+}
+
 static void test_introspection(struct kvm_vm *vm)
 {
 	srandom(time(0));
@@ -1928,6 +1957,7 @@ static void test_introspection(struct kvm_vm *vm)
 	test_cmd_vm_set_page_access(vm);
 	test_event_pf(vm);
 	test_cmd_vcpu_control_singlestep(vm);
+	test_cmd_translate_gva(vm);

 	unhook_introspection(vm);
 }