[PATCH 3/3] KVM: selftests: Test behavior of HWCR

[Jim Mattson <jmattson@google.com>]

Verify the following:
* Any bits that read as one cannot be cleared
* Attempts to set bits 3, 6, 8, or 24 are ignored
* Bit 18 is the only bit that can be set
* Any bit that can be set can also be cleared

Signed-off-by: Jim Mattson <jmattson@google.com>
---
 tools/testing/selftests/kvm/Makefile          |  1 +
 .../selftests/kvm/x86_64/hwcr_msr_test.c      | 57 +++++++++++++++++++
 2 files changed, 58 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c

diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index a3bb36fb3cfc..6b0219ca65eb 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -135,6 +135,7 @@ TEST_GEN_PROGS_x86_64 += set_memory_region_test
 TEST_GEN_PROGS_x86_64 += steal_time
 TEST_GEN_PROGS_x86_64 += kvm_binary_stats_test
 TEST_GEN_PROGS_x86_64 += system_counter_offset_test
+TEST_GEN_PROGS_x86_64 += x86_64/hwcr_msr_test
 
 # Compiled outputs used by test targets
 TEST_GEN_PROGS_EXTENDED_x86_64 += x86_64/nx_huge_pages_test
diff --git a/tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c b/tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c
new file mode 100644
index 000000000000..123267b44daf
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86_64/hwcr_msr_test.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2023, Google LLC.
+ *
+ * Tests for the K7_HWCR MSR.
+ */
+
+#define _GNU_SOURCE /* for program_invocation_short_name */
+#include <sys/ioctl.h>
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "vmx.h"
+
+void test_hwcr_bit(struct kvm_vcpu *vcpu, unsigned int bit)
+{
+	const unsigned long long ignored =
+		BIT_ULL(3) | BIT_ULL(6) | BIT_ULL(8) | BIT_ULL(24);
+	const unsigned long long legal = ignored | BIT_ULL(18);
+	uint64_t orig = vcpu_get_msr(vcpu, MSR_K7_HWCR);
+	uint64_t val = BIT_ULL(bit);
+	uint64_t check;
+	int r;
+
+	r = _vcpu_set_msr(vcpu, MSR_K7_HWCR, val);
+	TEST_ASSERT((r == 1 && (val & legal)) || (r == 0 && !(val & legal)),
+		    "Unexpected result (%d) when setting HWCR[bit %u]", r, bit);
+	check =	vcpu_get_msr(vcpu, MSR_K7_HWCR);
+	if (val & (legal & ~ignored)) {
+		TEST_ASSERT(check == (orig | val),
+			    "Bit %u: unexpected HWCR %lx; expected %lx", bit,
+			    check, orig | val);
+		_vcpu_set_msr(vcpu, MSR_K7_HWCR, 0);
+		check =	vcpu_get_msr(vcpu, MSR_K7_HWCR);
+		TEST_ASSERT(check == orig,
+			    "Bit %u: unexpected HWCR %lx; expected %lx", bit,
+			    check, orig);
+	} else {
+		TEST_ASSERT(check == orig,
+			    "Bit %u: unexpected HWCR %lx; expected %lx", bit,
+			    check, orig);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	unsigned int bit;
+
+	vm = vm_create_with_one_vcpu(&vcpu, NULL);
+
+	for (bit = 0; bit < BITS_PER_LONG; bit++)
+		test_hwcr_bit(vcpu, bit);
+
+	kvm_vm_free(vm);
+}
-- 
2.42.0.515.g380fc7ccd1-goog