KVM: selftests: Add global snapshot of kvm_is_forced_emulation_enabled()

Add a global snapshot of kvm_is_forced_emulation_enabled() and sync it to
all VMs by default so that core library code can force emulation, e.g. to
allow for easier testing of the intersections between emulation and other
features in KVM.

Link: https://lore.kernel.org/r/20240314185459.2439072-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

tools/testing/selftests/kvm/include/x86_64/kvm_util_arch.h

@@ -5,6 +5,8 @@
 #include <stdbool.h>
 #include <stdint.h>
 
+extern bool is_forced_emulation_enabled;
+
 struct kvm_vm_arch {
 	uint64_t c_bit;
 	uint64_t s_bit;

tools/testing/selftests/kvm/lib/x86_64/processor.c

@@ -23,6 +23,7 @@
 vm_vaddr_t exception_handlers;
 bool host_cpu_is_amd;
 bool host_cpu_is_intel;
+bool is_forced_emulation_enabled;
 
 static void regs_dump(FILE *stream, struct kvm_regs *regs, uint8_t indent)
 {
@@ -577,6 +578,7 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm)
 	vm_create_irqchip(vm);
 	sync_global_to_guest(vm, host_cpu_is_intel);
 	sync_global_to_guest(vm, host_cpu_is_amd);
+	sync_global_to_guest(vm, is_forced_emulation_enabled);
 
 	if (vm->type == KVM_X86_SEV_VM || vm->type == KVM_X86_SEV_ES_VM) {
 		struct kvm_sev_init init = { 0 };
@@ -1348,6 +1350,7 @@ void kvm_selftest_arch_init(void)
 {
 	host_cpu_is_intel = this_cpu_is_intel();
 	host_cpu_is_amd = this_cpu_is_amd();
+	is_forced_emulation_enabled = kvm_is_forced_emulation_enabled();
 }
 
 bool sys_clocksource_is_based_on_tsc(void)

tools/testing/selftests/kvm/x86_64/pmu_counters_test.c

@@ -19,7 +19,6 @@
 
 static uint8_t kvm_pmu_version;
 static bool kvm_has_perf_caps;
-static bool is_forced_emulation_enabled;
 
 static struct kvm_vm *pmu_vm_create_with_one_vcpu(struct kvm_vcpu **vcpu,
 						  void *guest_code,
@@ -33,7 +32,6 @@ static struct kvm_vm *pmu_vm_create_with_one_vcpu(struct kvm_vcpu **vcpu,
 	vcpu_init_descriptor_tables(*vcpu);
 
 	sync_global_to_guest(vm, kvm_pmu_version);
-	sync_global_to_guest(vm, is_forced_emulation_enabled);
 
 	/*
 	 * Set PERF_CAPABILITIES before PMU version as KVM disallows enabling
@@ -610,7 +608,6 @@ int main(int argc, char *argv[])
 
 	kvm_pmu_version = kvm_cpu_property(X86_PROPERTY_PMU_VERSION);
 	kvm_has_perf_caps = kvm_cpu_has(X86_FEATURE_PDCM);
-	is_forced_emulation_enabled = kvm_is_forced_emulation_enabled();
 
 	test_intel_counters();
 

tools/testing/selftests/kvm/x86_64/userspace_msr_exit_test.c

@@ -11,8 +11,6 @@
 #include "kvm_util.h"
 #include "vmx.h"
 
-static bool fep_available;
-
 #define MSR_NON_EXISTENT 0x474f4f00
 
 static u64 deny_bits = 0;
@@ -256,7 +254,7 @@ static void guest_code_filter_allow(void)
 	GUEST_ASSERT(data == 2);
 	GUEST_ASSERT(guest_exception_count == 0);
 
-	if (fep_available) {
+	if (is_forced_emulation_enabled) {
 		/* Let userspace know we aren't done. */
 		GUEST_SYNC(0);
 
@@ -518,8 +516,6 @@ KVM_ONE_VCPU_TEST(user_msr, msr_filter_allow, guest_code_filter_allow)
 	uint64_t cmd;
 	int rc;
 
-	sync_global_to_guest(vm, fep_available);
-
 	rc = kvm_check_cap(KVM_CAP_X86_USER_SPACE_MSR);
 	TEST_ASSERT(rc, "KVM_CAP_X86_USER_SPACE_MSR is available");
 	vm_enable_cap(vm, KVM_CAP_X86_USER_SPACE_MSR, KVM_MSR_EXIT_REASON_FILTER);
@@ -549,7 +545,7 @@ KVM_ONE_VCPU_TEST(user_msr, msr_filter_allow, guest_code_filter_allow)
 	vcpu_run(vcpu);
 	cmd = process_ucall(vcpu);
 
-	if (fep_available) {
+	if (is_forced_emulation_enabled) {
 		TEST_ASSERT_EQ(cmd, UCALL_SYNC);
 		vm_install_exception_handler(vm, GP_VECTOR, guest_fep_gp_handler);
 
@@ -772,7 +768,5 @@ KVM_ONE_VCPU_TEST(user_msr, user_exit_msr_flags, NULL)
 
 int main(int argc, char *argv[])
 {
-	fep_available = kvm_is_forced_emulation_enabled();
-
 	return test_harness_run(argc, argv);
 }