[RFC PATCH v3 21/31] KVM: selftests: TDX: Verify the behavior when host consumes a TD private memory

Ackerley Tng
2023-01-21T00:19:10Z

From: Ryan Afranji <afranji@google.com>

The test checks that host can only read fixed values when trying to
access the guest's private memory.

Signed-off-by: Ryan Afranji <afranji@google.com>
Signed-off-by: Sagi Shahar <sagis@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
.../selftests/kvm/x86_64/tdx_vm_tests.c | 85 +++++++++++++++++++
1 file changed, 85 insertions(+)

diff --git a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
index b9d96b5f6521f..4c338206dbaf2 100644
--- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
+++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
@@ -1069,6 +1069,90 @@ void verify_td_cpuid_tdcall(void)
printf("\t ... PASSED\n");
}

+/*
+ * Shared variables between guest and host for host reading private mem test
+ */
+static uint64_t tdx_test_host_read_private_mem_addr;
+#define TDX_HOST_READ_PRIVATE_MEM_PORT_TEST 0x53
+
+void guest_host_read_priv_mem(void)
+{
+ uint64_t ret;
+ uint64_t placeholder = 0;
+
+ /* Set value */
+ *((uint32_t *) tdx_test_host_read_private_mem_addr) = 0xABCD;
+
+ /* Exit so host can read value */
+ ret = tdg_vp_vmcall_instruction_io(
+ TDX_HOST_READ_PRIVATE_MEM_PORT_TEST, 4,
+ TDG_VP_VMCALL_INSTRUCTION_IO_WRITE, &placeholder);
+ if (ret)
+ tdx_test_fatal(ret);
+
+ /* Update guest_var's value and have host reread it. */
+ *((uint32_t *) tdx_test_host_read_private_mem_addr) = 0xFEDC;
+
+ tdx_test_success();
+}
+
+void verify_host_reading_private_mem(void)
+{
+ struct kvm_vm *vm;
+ struct kvm_vcpu *vcpu;
+
+ vm_vaddr_t test_page;
+ uint64_t *host_virt;
+ uint64_t first_host_read;
+ uint64_t second_host_read;
+
+ vm = td_create();
+ td_initialize(vm, VM_MEM_SRC_ANONYMOUS, 0);
+ vcpu = td_vcpu_add(vm, 0, guest_host_read_priv_mem);
+
+ test_page = vm_vaddr_alloc_page(vm);
+ TEST_ASSERT(test_page < BIT_ULL(32),
+ "Test address should fit in 32 bits so it can be sent to the guest");
+
+ host_virt = addr_gva2hva(vm, test_page);
+ TEST_ASSERT(host_virt != NULL,
+ "Guest address not found in guest memory regions\n");
+
+ tdx_test_host_read_private_mem_addr = test_page;
+ sync_global_to_guest(vm, tdx_test_host_read_private_mem_addr);
+
+ td_finalize(vm);
+
+ printf("Verifying host's behavior when reading TD private memory:\n");
+
+ vcpu_run(vcpu);
+ TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
+ TDX_TEST_ASSERT_IO(vcpu, TDX_HOST_READ_PRIVATE_MEM_PORT_TEST,
+ 4, TDG_VP_VMCALL_INSTRUCTION_IO_WRITE);
+ printf("\t ... Guest's variable contains 0xABCD\n");
+
+ /* Host reads guest's variable. */
+ first_host_read = *host_virt;
+ printf("\t ... Host's read attempt value: %lu\n", first_host_read);
+
+ /* Guest updates variable and host rereads it. */
+ vcpu_run(vcpu);
+ TDX_TEST_CHECK_GUEST_FAILURE(vcpu);
+ printf("\t ... Guest's variable updated to 0xFEDC\n");
+
+ second_host_read = *host_virt;
+ printf("\t ... Host's second read attempt value: %lu\n",
+ second_host_read);
+
+ TEST_ASSERT(first_host_read == second_host_read,
+ "Host did not read a fixed pattern\n");
+
+ printf("\t ... Fixed pattern was returned to the host\n");
+
+ kvm_vm_free(vm);
+ printf("\t ... PASSED\n");
+}
+
int main(int argc, char **argv)
{
setbuf(stdout, NULL);
@@ -1091,6 +1175,7 @@ int main(int argc, char **argv)
run_in_new_process(&verify_mmio_reads);
run_in_new_process(&verify_mmio_writes);
run_in_new_process(&verify_td_cpuid_tdcall);
+ run_in_new_process(&verify_host_reading_private_mem);

return 0;
}
--
2.39.0.246.g2a6d74b583-goog