[PATCH v4 4/4] KVM: selftests: KVM: SVM: Add Idle HLT intercept test

[Manali Shukla <manali.shukla@amd.com>]

From: Manali Shukla <Manali.Shukla@amd.com>

Execution of the HLT instruction results in VMEXIT. Hypervisor observes
pending V_INTR and V_NMI events just after VMEXIT generated by HLT for
the vCPU and causes VM entry to service the pending events.  The Idle
HLT intercept feature avoids the wasteful VMEXIT during halt if there
are pending V_INTR and V_NMI events for the vCPU.

The selftest for Idle HLT intercept instruments above-mentioned scenario.

Signed-off-by: Manali Shukla <Manali.Shukla@amd.com>
---
 tools/testing/selftests/kvm/Makefile          |  1 +
 .../selftests/kvm/include/x86_64/processor.h  |  1 +
 .../selftests/kvm/x86_64/svm_idle_hlt_test.c  | 89 +++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/x86_64/svm_idle_hlt_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index 960cf6a77198..25e4bc9473d5 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -94,6 +94,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/smaller_maxphyaddr_emulation_test
 TEST_GEN_PROGS_x86_64 += x86_64/smm_test
 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_idle_hlt_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_shutdown_test
diff --git a/tools/testing/selftests/kvm/include/x86_64/processor.h b/tools/testing/selftests/kvm/include/x86_64/processor.h
index 8e36de85b68f..41815d6ae500 100644
--- a/tools/testing/selftests/kvm/include/x86_64/processor.h
+++ b/tools/testing/selftests/kvm/include/x86_64/processor.h
@@ -197,6 +197,7 @@ struct kvm_x86_cpu_feature {
 #define X86_FEATURE_PAUSEFILTER         KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 10)
 #define X86_FEATURE_PFTHRESHOLD         KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 12)
 #define	X86_FEATURE_VGIF		KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 16)
+#define X86_FEATURE_IDLE_HLT		KVM_X86_CPU_FEATURE(0x8000000A, 0, EDX, 30)
 #define X86_FEATURE_SEV			KVM_X86_CPU_FEATURE(0x8000001F, 0, EAX, 1)
 #define X86_FEATURE_SEV_ES		KVM_X86_CPU_FEATURE(0x8000001F, 0, EAX, 3)
 
diff --git a/tools/testing/selftests/kvm/x86_64/svm_idle_hlt_test.c b/tools/testing/selftests/kvm/x86_64/svm_idle_hlt_test.c
new file mode 100644
index 000000000000..fe2ea96695e4
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/svm_idle_hlt_test.c
@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 2024 Advanced Micro Devices, Inc.
+ *
+ */
+#include <kvm_util.h>
+#include <processor.h>
+#include <test_util.h>
+#include "svm_util.h"
+#include "apic.h"
+
+#define VINTR_VECTOR     0x30
+#define NUM_ITERATIONS   1000
+
+static bool irq_received;
+
+/*
+ * The guest code instruments the scenario where there is a V_INTR pending
+ * event available while hlt instruction is executed. The HLT VM Exit doesn't
+ * occur in above-mentioned scenario if Idle HLT intercept feature is enabled.
+ */
+
+static void guest_code(void)
+{
+	uint32_t icr_val;
+	int i;
+
+	xapic_enable();
+
+	icr_val = (APIC_DEST_SELF | APIC_INT_ASSERT | VINTR_VECTOR);
+
+	for (i = 0; i < NUM_ITERATIONS; i++) {
+		cli();
+		xapic_write_reg(APIC_ICR, icr_val);
+		safe_halt();
+		GUEST_ASSERT(READ_ONCE(irq_received));
+		WRITE_ONCE(irq_received, false);
+	}
+	GUEST_DONE();
+}
+
+static void guest_vintr_handler(struct ex_regs *regs)
+{
+	WRITE_ONCE(irq_received, true);
+	xapic_write_reg(APIC_EOI, 0x00);
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	struct ucall uc;
+	uint64_t  halt_exits, vintr_exits;
+
+	/* Check the extension for binary stats */
+	TEST_REQUIRE(this_cpu_has(X86_FEATURE_IDLE_HLT));
+	TEST_REQUIRE(kvm_has_cap(KVM_CAP_BINARY_STATS_FD));
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+
+	vm_install_exception_handler(vm, VINTR_VECTOR, guest_vintr_handler);
+	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
+
+	vcpu_run(vcpu);
+	TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+	halt_exits = vcpu_get_stat(vcpu, halt_exits);
+	vintr_exits = vcpu_get_stat(vcpu, irq_window_exits);
+
+	switch (get_ucall(vcpu, &uc)) {
+	case UCALL_ABORT:
+		REPORT_GUEST_ASSERT(uc);
+		/* NOT REACHED */
+	case UCALL_DONE:
+		break;
+
+	default:
+		TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
+	}
+
+	TEST_ASSERT_EQ(halt_exits, 0);
+	pr_debug("Guest executed VINTR followed by halts: %d times.\n"
+		 "The guest exited due to halt: %ld times and number\n"
+		 "of vintr exits: %ld.\n",
+		 NUM_ITERATIONS, halt_exits, vintr_exits);
+
+	kvm_vm_free(vm);
+	return 0;
+}
-- 
2.34.1