[PATCH 8/8] KVM: selftests: nSVM: Add svm_nested_soft_inject_test

Sean Christopherson
2022-04-02T01:09:49Z

From: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>

Add a KVM self-test that checks whether a nSVM L1 is able to successfully
inject a software interrupt and a soft exception into its L2 guest.

In practice, this tests both the next_rip field consistency and
L1-injected event with intervening L0 VMEXIT during its delivery:
the first nested VMRUN (that's also trying to inject a software interrupt)
will immediately trigger a L0 NPF.
This L0 NPF will have zero in its CPU-returned next_rip field, which if
incorrectly reused by KVM will trigger a #PF when trying to return to
such address 0 from the interrupt handler.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/.gitignore | 1 +
tools/testing/selftests/kvm/Makefile | 1 +
.../selftests/kvm/include/x86_64/svm_util.h | 2 +
.../kvm/x86_64/svm_nested_soft_inject_test.c | 147 ++++++++++++++++++
4 files changed, 151 insertions(+)
create mode 100644 tools/testing/selftests/kvm/x86_64/svm_nested_soft_inject_test.c

diff --git a/tools/testing/selftests/kvm/.gitignore b/tools/testing/selftests/kvm/.gitignore
index 1f1b6c978bf7..1354d3f4a362 100644
--- a/tools/testing/selftests/kvm/.gitignore
+++ b/tools/testing/selftests/kvm/.gitignore
@@ -33,6 +33,7 @@
/x86_64/state_test
/x86_64/svm_vmcall_test
/x86_64/svm_int_ctl_test
+/x86_64/svm_nested_soft_inject_test
/x86_64/sync_regs_test
/x86_64/tsc_msrs_test
/x86_64/userspace_io_test
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index c9cdbd248727..cef6d583044b 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -66,6 +66,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/state_test
TEST_GEN_PROGS_x86_64 += x86_64/vmx_preemption_timer_test
TEST_GEN_PROGS_x86_64 += x86_64/svm_vmcall_test
TEST_GEN_PROGS_x86_64 += x86_64/svm_int_ctl_test
+TEST_GEN_PROGS_x86_64 += x86_64/svm_nested_soft_inject_test
TEST_GEN_PROGS_x86_64 += x86_64/tsc_scaling_sync
TEST_GEN_PROGS_x86_64 += x86_64/sync_regs_test
TEST_GEN_PROGS_x86_64 += x86_64/userspace_io_test
diff --git a/tools/testing/selftests/kvm/include/x86_64/svm_util.h b/tools/testing/selftests/kvm/include/x86_64/svm_util.h
index a25aabd8f5e7..d49f7c9b4564 100644
--- a/tools/testing/selftests/kvm/include/x86_64/svm_util.h
+++ b/tools/testing/selftests/kvm/include/x86_64/svm_util.h
@@ -16,6 +16,8 @@
#define CPUID_SVM_BIT 2
#define CPUID_SVM BIT_ULL(CPUID_SVM_BIT)

+#define SVM_EXIT_EXCP_BASE 0x040
+#define SVM_EXIT_HLT 0x078
#define SVM_EXIT_MSR 0x07c
#define SVM_EXIT_VMMCALL 0x081

diff --git a/tools/testing/selftests/kvm/x86_64/svm_nested_soft_inject_test.c b/tools/testing/selftests/kvm/x86_64/svm_nested_soft_inject_test.c
new file mode 100644
index 000000000000..d39be5d885c1
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/svm_nested_soft_inject_test.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022 Oracle and/or its affiliates.
+ *
+ * Based on:
+ * svm_int_ctl_test
+ *
+ * Copyright (C) 2021, Red Hat, Inc.
+ *
+ */
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "svm_util.h"
+
+#define VCPU_ID 0
+#define INT_NR 0x20
+#define X86_FEATURE_NRIPS BIT(3)
+
+#define vmcall() \
+ __asm__ __volatile__( \
+ "vmmcall\n" \
+ )
+
+#define ud2() \
+ __asm__ __volatile__( \
+ "ud2\n" \
+ )
+
+#define hlt() \
+ __asm__ __volatile__( \
+ "hlt\n" \
+ )
+
+static unsigned int bp_fired;
+static void guest_bp_handler(struct ex_regs *regs)
+{
+ bp_fired++;
+}
+
+static unsigned int int_fired;
+static void guest_int_handler(struct ex_regs *regs)
+{
+ int_fired++;
+}
+
+static void l2_guest_code(void)
+{
+ GUEST_ASSERT(int_fired == 1);
+ vmcall();
+ ud2();
+
+ GUEST_ASSERT(bp_fired == 1);
+ hlt();
+}
+
+static void l1_guest_code(struct svm_test_data *svm)
+{
+ #define L2_GUEST_STACK_SIZE 64
+ unsigned long l2_guest_stack[L2_GUEST_STACK_SIZE];
+ struct vmcb *vmcb = svm->vmcb;
+
+ /* Prepare for L2 execution. */
+ generic_svm_setup(svm, l2_guest_code,
+ &l2_guest_stack[L2_GUEST_STACK_SIZE]);
+
+ vmcb->control.intercept_exceptions |= BIT(PF_VECTOR) | BIT(UD_VECTOR);
+ vmcb->control.intercept |= BIT(INTERCEPT_HLT);
+
+ vmcb->control.event_inj = INT_NR | SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_SOFT;
+ /* The return address pushed on stack */
+ vmcb->control.next_rip = vmcb->save.rip;
+
+ run_guest(vmcb, svm->vmcb_gpa);
+ GUEST_ASSERT_3(vmcb->control.exit_code == SVM_EXIT_VMMCALL,
+ vmcb->control.exit_code,
+ vmcb->control.exit_info_1, vmcb->control.exit_info_2);
+
+ /* Skip over VMCALL */
+ vmcb->save.rip += 3;
+
+ vmcb->control.event_inj = BP_VECTOR | SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_EXEPT;
+ /* The return address pushed on stack, skip over UD2 */
+ vmcb->control.next_rip = vmcb->save.rip + 2;
+
+ run_guest(vmcb, svm->vmcb_gpa);
+ GUEST_ASSERT_3(vmcb->control.exit_code == SVM_EXIT_HLT,
+ vmcb->control.exit_code,
+ vmcb->control.exit_info_1, vmcb->control.exit_info_2);
+
+ GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+ struct kvm_cpuid_entry2 *cpuid;
+ struct kvm_vm *vm;
+ vm_vaddr_t svm_gva;
+ struct kvm_guest_debug debug;
+
+ nested_svm_check_supported();
+
+ cpuid = kvm_get_supported_cpuid_entry(0x8000000a);
+ if (!(cpuid->edx & X86_FEATURE_NRIPS)) {
+ print_skip("nRIP Save unavailable");
+ exit(KSFT_SKIP);
+ }
+
+ vm = vm_create_default(VCPU_ID, 0, (void *) l1_guest_code);
+
+ vm_init_descriptor_tables(vm);
+ vcpu_init_descriptor_tables(vm, VCPU_ID);
+
+ vm_install_exception_handler(vm, BP_VECTOR, guest_bp_handler);
+ vm_install_exception_handler(vm, INT_NR, guest_int_handler);
+
+ vcpu_alloc_svm(vm, &svm_gva);
+ vcpu_args_set(vm, VCPU_ID, 1, svm_gva);
+
+ memset(&debug, 0, sizeof(debug));
+ vcpu_set_guest_debug(vm, VCPU_ID, &debug);
+
+ struct kvm_run *run = vcpu_state(vm, VCPU_ID);
+ struct ucall uc;
+
+ vcpu_run(vm, VCPU_ID);
+ TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
+ "Got exit_reason other than KVM_EXIT_IO: %u (%s)\n",
+ run->exit_reason,
+ exit_reason_str(run->exit_reason));
+
+ switch (get_ucall(vm, VCPU_ID, &uc)) {
+ case UCALL_ABORT:
+ TEST_FAIL("%s at %s:%ld, vals = 0x%lx 0x%lx 0x%lx", (const char *)uc.args[0],
+ __FILE__, uc.args[1], uc.args[2], uc.args[3], uc.args[4]);
+ break;
+ /* NOT REACHED */
+ case UCALL_DONE:
+ goto done;
+ default:
+ TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
+ }
+done:
+ kvm_vm_free(vm);
+ return 0;
+}
--
2.35.1.1094.g7c7d902a7c-goog