[RFC PATCH v2 15/17] KVM: selftest: TDX: Verify the behavior when host consumes a TD private memory

Sagi Shahar
2022-08-30T22:22:24Z

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>
---
.../selftests/kvm/x86_64/tdx_vm_tests.c | 93 +++++++++++++++++++
1 file changed, 93 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 934f2f7a5df9..1776b39b7d9e 100644
--- a/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
+++ b/tools/testing/selftests/kvm/x86_64/tdx_vm_tests.c
@@ -1274,6 +1274,98 @@ void verify_mmio_writes(void)
printf("\t ... PASSED\n");
}

+TDX_GUEST_FUNCTION(guest_host_read_priv_mem)
+{
+ uint64_t guest_var = 0xABCD;
+ uint64_t ret;
+
+ /* Sends address to host. */
+ ret = tdvm_report_64bit_to_user_space((uint64_t)&guest_var);
+ if (ret)
+ tdvmcall_fatal(ret);
+
+ /* Update guest_var's value and have host reread it. */
+ guest_var = 0xFEDC;
+
+ tdvmcall_success();
+}
+
+void verify_host_reading_private_mem(void)
+{
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ struct userspace_mem_region *region;
+ uint64_t guest_var_addr;
+ uint64_t host_virt;
+ uint64_t first_host_read;
+ uint64_t second_host_read;
+ int ctr;
+
+ printf("Verifying host's behavior when reading TD private memory:\n");
+ /* Create a TD VM with no memory. */
+ vm = vm_create_tdx();
+
+ /* Allocate TD guest memory and initialize the TD. */
+ initialize_td(vm);
+
+ /* Initialize the TD vcpu and copy the test code to the guest memory. */
+ vcpu = vm_vcpu_add_tdx(vm, 0);
+
+ /* Setup and initialize VM memory. */
+ prepare_source_image(vm, guest_host_read_priv_mem,
+ TDX_FUNCTION_SIZE(guest_host_read_priv_mem), 0);
+ finalize_td_memory(vm);
+
+ /* Get the address of the guest's variable. */
+ vcpu_run(vcpu);
+ CHECK_GUEST_FAILURE(vcpu);
+ printf("\t ... Guest's variable contains 0xABCD\n");
+
+ /* Guest virtual and guest physical addresses have 1:1 mapping. */
+ guest_var_addr = read_64bit_from_guest(vcpu, TDX_DATA_REPORT_PORT);
+
+ /* Search for the guest's address in guest's memory regions. */
+ host_virt = 0;
+ hash_for_each(vm->regions.slot_hash, ctr, region, slot_node) {
+ uint64_t offset;
+ uint64_t host_virt_base;
+ uint64_t guest_base;
+
+ guest_base = (uint64_t)region->region.guest_phys_addr;
+ offset = guest_var_addr - guest_base;
+
+ if (guest_base <= guest_var_addr &&
+ offset <= region->region.memory_size) {
+ host_virt_base = (uint64_t)region->host_mem;
+ host_virt = host_virt_base + offset;
+ break;
+ }
+ }
+ TEST_ASSERT(host_virt != 0,
+ "Guest address not found in guest memory regions\n");
+
+ /* Host reads guest's variable. */
+ first_host_read = *(uint64_t *)host_virt;
+ printf("\t ... Host's read attempt value: %lu\n", first_host_read);
+
+ /* Guest updates variable and host rereads it. */
+ vcpu_run(vcpu);
+ CHECK_GUEST_FAILURE(vcpu);
+ printf("\t ... Guest's variable updated to 0xFEDC\n");
+
+ second_host_read = *(uint64_t *)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)
{
if (!is_tdx_enabled()) {
@@ -1294,6 +1386,7 @@ int main(int argc, char **argv)
run_in_new_process(&verify_guest_hlt);
run_in_new_process(&verify_mmio_reads);
run_in_new_process(&verify_mmio_writes);
+ run_in_new_process(&verify_host_reading_private_mem);

return 0;
}
--
2.37.2.789.g6183377224-goog