KVM: selftests: Add test to verify KVM handling of ICR

The main thing that the selftest verifies is that KVM copies x2APIC's
ICR[63:32] to/from ICR2 when userspace accesses the vAPIC page via
KVM_{G,S}ET_LAPIC.  KVM previously split x2APIC ICR to ICR+ICR2 at the
time of write (from the guest), and so KVM must preserve that behavior
for backwards compatibility between different versions of KVM.

It will also test other invariants, e.g. that KVM clears the BUSY
flag on ICR writes, that the reserved bits in ICR2 are dropped on writes
from the guest, etc...
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20220204214205.3306634-12-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/.gitignore

@@ -46,6 +46,7 @@
 /x86_64/vmx_tsc_adjust_test
 /x86_64/vmx_nested_tsc_scaling_test
 /x86_64/xapic_ipi_test
+/x86_64/xapic_state_test
 /x86_64/xen_shinfo_test
 /x86_64/xen_vmcall_test
 /x86_64/xss_msr_test

tools/testing/selftests/kvm/Makefile

@@ -77,6 +77,7 @@ TEST_GEN_PROGS_x86_64 += x86_64/vmx_set_nested_state_test
 TEST_GEN_PROGS_x86_64 += x86_64/vmx_tsc_adjust_test
 TEST_GEN_PROGS_x86_64 += x86_64/vmx_nested_tsc_scaling_test
 TEST_GEN_PROGS_x86_64 += x86_64/xapic_ipi_test
+TEST_GEN_PROGS_x86_64 += x86_64/xapic_state_test
 TEST_GEN_PROGS_x86_64 += x86_64/xss_msr_test
 TEST_GEN_PROGS_x86_64 += x86_64/debug_regs
 TEST_GEN_PROGS_x86_64 += x86_64/tsc_msrs_test

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

@@ -33,6 +33,7 @@
 #define	APIC_SPIV	0xF0
 #define		APIC_SPIV_FOCUS_DISABLED	(1 << 9)
 #define		APIC_SPIV_APIC_ENABLED		(1 << 8)
+#define APIC_IRR	0x200
 #define	APIC_ICR	0x300
 #define		APIC_DEST_SELF		0x40000
 #define		APIC_DEST_ALLINC	0x80000

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

+// SPDX-License-Identifier: GPL-2.0-only
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+
+#include "apic.h"
+#include "kvm_util.h"
+#include "processor.h"
+#include "test_util.h"
+
+struct kvm_vcpu {
+	uint32_t id;
+	bool is_x2apic;
+};
+
+static void xapic_guest_code(void)
+{
+	asm volatile("cli");
+
+	xapic_enable();
+
+	while (1) {
+		uint64_t val = (u64)xapic_read_reg(APIC_IRR) |
+			       (u64)xapic_read_reg(APIC_IRR + 0x10) << 32;
+
+		xapic_write_reg(APIC_ICR2, val >> 32);
+		xapic_write_reg(APIC_ICR, val);
+		GUEST_SYNC(val);
+	}
+}
+
+static void x2apic_guest_code(void)
+{
+	asm volatile("cli");
+
+	x2apic_enable();
+
+	do {
+		uint64_t val = x2apic_read_reg(APIC_IRR) |
+			       x2apic_read_reg(APIC_IRR + 0x10) << 32;
+
+		x2apic_write_reg(APIC_ICR, val);
+		GUEST_SYNC(val);
+	} while (1);
+}
+
+static void ____test_icr(struct kvm_vm *vm, struct kvm_vcpu *vcpu, uint64_t val)
+{
+	struct kvm_lapic_state xapic;
+	struct ucall uc;
+	uint64_t icr;
+
+	/*
+	 * Tell the guest what ICR value to write.  Use the IRR to pass info,
+	 * all bits are valid and should not be modified by KVM (ignoring the
+	 * fact that vectors 0-15 are technically illegal).
+	 */
+	vcpu_ioctl(vm, vcpu->id, KVM_GET_LAPIC, &xapic);
+	*((u32 *)&xapic.regs[APIC_IRR]) = val;
+	*((u32 *)&xapic.regs[APIC_IRR + 0x10]) = val >> 32;
+	vcpu_ioctl(vm, vcpu->id, KVM_SET_LAPIC, &xapic);
+
+	vcpu_run(vm, vcpu->id);
+	ASSERT_EQ(get_ucall(vm, vcpu->id, &uc), UCALL_SYNC);
+	ASSERT_EQ(uc.args[1], val);
+
+	vcpu_ioctl(vm, vcpu->id, KVM_GET_LAPIC, &xapic);
+	icr = (u64)(*((u32 *)&xapic.regs[APIC_ICR])) |
+	      (u64)(*((u32 *)&xapic.regs[APIC_ICR2])) << 32;
+	if (!vcpu->is_x2apic)
+		val &= (-1u | (0xffull << (32 + 24)));
+	ASSERT_EQ(icr, val & ~APIC_ICR_BUSY);
+}
+
+static void __test_icr(struct kvm_vm *vm, struct kvm_vcpu *vcpu, uint64_t val)
+{
+	____test_icr(vm, vcpu, val | APIC_ICR_BUSY);
+	____test_icr(vm, vcpu, val & ~(u64)APIC_ICR_BUSY);
+}
+
+static void test_icr(struct kvm_vm *vm, struct kvm_vcpu *vcpu)
+{
+	uint64_t icr, i, j;
+
+	icr = APIC_DEST_SELF | APIC_INT_ASSERT | APIC_DM_FIXED;
+	for (i = 0; i <= 0xff; i++)
+		__test_icr(vm, vcpu, icr | i);
+
+	icr = APIC_INT_ASSERT | APIC_DM_FIXED;
+	for (i = 0; i <= 0xff; i++)
+		__test_icr(vm, vcpu, icr | i);
+
+	/*
+	 * Send all flavors of IPIs to non-existent vCPUs.  TODO: use number of
+	 * vCPUs, not vcpu.id + 1.  Arbitrarily use vector 0xff.
+	 */
+	icr = APIC_INT_ASSERT | 0xff;
+	for (i = vcpu->id + 1; i < 0xff; i++) {
+		for (j = 0; j < 8; j++)
+			__test_icr(vm, vcpu, i << (32 + 24) | APIC_INT_ASSERT | (j << 8));
+	}
+
+	/* And again with a shorthand destination for all types of IPIs. */
+	icr = APIC_DEST_ALLBUT | APIC_INT_ASSERT;
+	for (i = 0; i < 8; i++)
+		__test_icr(vm, vcpu, icr | (i << 8));
+
+	/* And a few garbage value, just make sure it's an IRQ (blocked). */
+	__test_icr(vm, vcpu, 0xa5a5a5a5a5a5a5a5 & ~APIC_DM_FIXED_MASK);
+	__test_icr(vm, vcpu, 0x5a5a5a5a5a5a5a5a & ~APIC_DM_FIXED_MASK);
+	__test_icr(vm, vcpu, -1ull & ~APIC_DM_FIXED_MASK);
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vcpu vcpu = {
+		.id = 0,
+		.is_x2apic = true,
+	};
+	struct kvm_cpuid2 *cpuid;
+	struct kvm_vm *vm;
+	int i;
+
+	vm = vm_create_default(vcpu.id, 0, x2apic_guest_code);
+	test_icr(vm, &vcpu);
+	kvm_vm_free(vm);
+
+	/*
+	 * Use a second VM for the xAPIC test so that x2APIC can be hidden from
+	 * the guest in order to test AVIC.  KVM disallows changing CPUID after
+	 * KVM_RUN and AVIC is disabled if _any_ vCPU is allowed to use x2APIC.
+	 */
+	vm = vm_create_default(vcpu.id, 0, xapic_guest_code);
+	vcpu.is_x2apic = false;
+
+	cpuid = vcpu_get_cpuid(vm, vcpu.id);
+	for (i = 0; i < cpuid->nent; i++) {
+		if (cpuid->entries[i].function == 1)
+			break;
+	}
+	cpuid->entries[i].ecx &= ~BIT(21);
+	vcpu_set_cpuid(vm, vcpu.id, cpuid);
+
+	virt_pg_map(vm, APIC_DEFAULT_GPA, APIC_DEFAULT_GPA);
+	test_icr(vm, &vcpu);
+	kvm_vm_free(vm);
+}