KVM: arm64: Add selftest checking how the absence of GICv3 is handled

Given how tortuous and fragile the whole lack-of-GICv3 story is,
add a selftest checking that we don't regress it.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240827152517.3909653-12-maz@kernel.orgSigned-off-by: Marc Zyngier <maz@kernel.org>

tools/testing/selftests/kvm/Makefile

@@ -163,6 +163,7 @@ TEST_GEN_PROGS_aarch64 += aarch64/vgic_init
 TEST_GEN_PROGS_aarch64 += aarch64/vgic_irq
 TEST_GEN_PROGS_aarch64 += aarch64/vgic_lpi_stress
 TEST_GEN_PROGS_aarch64 += aarch64/vpmu_counter_access
+TEST_GEN_PROGS_aarch64 += aarch64/no-vgic-v3
 TEST_GEN_PROGS_aarch64 += access_tracking_perf_test
 TEST_GEN_PROGS_aarch64 += arch_timer
 TEST_GEN_PROGS_aarch64 += demand_paging_test

tools/testing/selftests/kvm/aarch64/no-vgic-v3.c

+// SPDX-License-Identifier: GPL-2.0
+
+// Check that, on a GICv3 system, not configuring GICv3 correctly
+// results in all of the sysregs generating an UNDEF exception.
+
+#include <test_util.h>
+#include <kvm_util.h>
+#include <processor.h>
+
+static volatile bool handled;
+
+#define __check_sr_read(r)					\
+	({							\
+		uint64_t val;					\
+								\
+		handled = false;				\
+		dsb(sy);					\
+		val = read_sysreg_s(SYS_ ## r);			\
+		val;						\
+	})
+
+#define __check_sr_write(r)					\
+	do {							\
+		handled = false;				\
+		dsb(sy);					\
+		write_sysreg_s(0, SYS_ ## r);			\
+		isb();						\
+	} while(0)
+
+/* Fatal checks */
+#define check_sr_read(r)					\
+	do {							\
+		__check_sr_read(r);				\
+		__GUEST_ASSERT(handled, #r " no read trap");	\
+	} while(0)
+
+#define check_sr_write(r)					\
+	do {							\
+		__check_sr_write(r);				\
+		__GUEST_ASSERT(handled, #r " no write trap");	\
+	} while(0)
+
+#define check_sr_rw(r)				\
+	do {					\
+		check_sr_read(r);		\
+		check_sr_write(r);		\
+	} while(0)
+
+static void guest_code(void)
+{
+	uint64_t val;
+
+	/*
+	 * Check that we advertise that ID_AA64PFR0_EL1.GIC == 0, having
+	 * hidden the feature at runtime without any other userspace action.
+	 */
+	__GUEST_ASSERT(FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_GIC),
+				 read_sysreg(id_aa64pfr0_el1)) == 0,
+		       "GICv3 wrongly advertised");
+
+	/*
+	 * Access all GICv3 registers, and fail if we don't get an UNDEF.
+	 * Note that we happily access all the APxRn registers without
+	 * checking their existance, as all we want to see is a failure.
+	 */
+	check_sr_rw(ICC_PMR_EL1);
+	check_sr_read(ICC_IAR0_EL1);
+	check_sr_write(ICC_EOIR0_EL1);
+	check_sr_rw(ICC_HPPIR0_EL1);
+	check_sr_rw(ICC_BPR0_EL1);
+	check_sr_rw(ICC_AP0R0_EL1);
+	check_sr_rw(ICC_AP0R1_EL1);
+	check_sr_rw(ICC_AP0R2_EL1);
+	check_sr_rw(ICC_AP0R3_EL1);
+	check_sr_rw(ICC_AP1R0_EL1);
+	check_sr_rw(ICC_AP1R1_EL1);
+	check_sr_rw(ICC_AP1R2_EL1);
+	check_sr_rw(ICC_AP1R3_EL1);
+	check_sr_write(ICC_DIR_EL1);
+	check_sr_read(ICC_RPR_EL1);
+	check_sr_write(ICC_SGI1R_EL1);
+	check_sr_write(ICC_ASGI1R_EL1);
+	check_sr_write(ICC_SGI0R_EL1);
+	check_sr_read(ICC_IAR1_EL1);
+	check_sr_write(ICC_EOIR1_EL1);
+	check_sr_rw(ICC_HPPIR1_EL1);
+	check_sr_rw(ICC_BPR1_EL1);
+	check_sr_rw(ICC_CTLR_EL1);
+	check_sr_rw(ICC_IGRPEN0_EL1);
+	check_sr_rw(ICC_IGRPEN1_EL1);
+
+	/*
+	 * ICC_SRE_EL1 may not be trappable, as ICC_SRE_EL2.Enable can
+	 * be RAO/WI. Engage in non-fatal accesses, starting with a
+	 * write of 0 to try and disable SRE, and let's see if it
+	 * sticks.
+	 */
+	__check_sr_write(ICC_SRE_EL1);
+	if (!handled)
+		GUEST_PRINTF("ICC_SRE_EL1 write not trapping (OK)\n");
+
+	val = __check_sr_read(ICC_SRE_EL1);
+	if (!handled) {
+		__GUEST_ASSERT((val & BIT(0)),
+			       "ICC_SRE_EL1 not trapped but ICC_SRE_EL1.SRE not set\n");
+		GUEST_PRINTF("ICC_SRE_EL1 read not trapping (OK)\n");
+	}
+
+	GUEST_DONE();
+}
+
+static void guest_undef_handler(struct ex_regs *regs)
+{
+	/* Success, we've gracefully exploded! */
+	handled = true;
+	regs->pc += 4;
+}
+
+static void test_run_vcpu(struct kvm_vcpu *vcpu)
+{
+	struct ucall uc;
+
+	do {
+		vcpu_run(vcpu);
+
+		switch (get_ucall(vcpu, &uc)) {
+		case UCALL_ABORT:
+			REPORT_GUEST_ASSERT(uc);
+			break;
+		case UCALL_PRINTF:
+			printf("%s", uc.buffer);
+			break;
+		case UCALL_DONE:
+			break;
+		default:
+			TEST_FAIL("Unknown ucall %lu", uc.cmd);
+		}
+	} while (uc.cmd != UCALL_DONE);
+}
+
+static void test_guest_no_gicv3(void)
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+
+	/* Create a VM without a GICv3 */
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+
+	vm_init_descriptor_tables(vm);
+	vcpu_init_descriptor_tables(vcpu);
+
+	vm_install_sync_handler(vm, VECTOR_SYNC_CURRENT,
+				ESR_EC_UNKNOWN, guest_undef_handler);
+
+	test_run_vcpu(vcpu);
+
+	kvm_vm_free(vm);
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vcpu *vcpu;
+	struct kvm_vm *vm;
+	uint64_t pfr0;
+
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+	vcpu_get_reg(vcpu, KVM_ARM64_SYS_REG(SYS_ID_AA64PFR0_EL1), &pfr0);
+	__TEST_REQUIRE(FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1_GIC), pfr0),
+		       "GICv3 not supported.");
+	kvm_vm_free(vm);
+
+	test_guest_no_gicv3();
+
+	return 0;
+}