[PATCH v2 13/16] KVM: riscv: selftests: Add csr emulation test

[Charlie Jenkins via B4 Relay <devnull+thecharlesjenkins.gmail.com@kernel.org>]

From: Charlie Jenkins <thecharlesjenkins@gmail.com>

Introduce a kvm test that uses the emulated test csr to validate that
all emulated reads/writes to csrs function as expected.

Signed-off-by: Charlie Jenkins <thecharlesjenkins@gmail.com>
---
 tools/testing/selftests/kvm/Makefile.kvm     |   1 +
 tools/testing/selftests/kvm/riscv/csr_test.c | 126 +++++++++++++++++++++++++++
 2 files changed, 127 insertions(+)

diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index 07a5fc2bf67c..88ccd15e8f94 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -212,6 +212,7 @@ TEST_GEN_PROGS_s390 += s390/irq_routing
 TEST_GEN_PROGS_s390 += mmu_stress_test
 
 TEST_GEN_PROGS_riscv = $(TEST_GEN_PROGS_COMMON)
+TEST_GEN_PROGS_riscv += riscv/csr_test
 TEST_GEN_PROGS_riscv += riscv/sbi_pmu_test
 TEST_GEN_PROGS_riscv += riscv/ebreak_test
 TEST_GEN_PROGS_riscv += riscv/mmio_test
diff --git a/tools/testing/selftests/kvm/riscv/csr_test.c b/tools/testing/selftests/kvm/riscv/csr_test.c
new file mode 100644
index 000000000000..b3e8b99b6e92
--- /dev/null
+++ b/tools/testing/selftests/kvm/riscv/csr_test.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * csr_test.c - Tests the csr functionality.
+ */
+#include "kvm_util.h"
+#include "ucall_common.h"
+
+#define CSR_TEST 0x240
+#define FP 0x00006000
+
+/*
+ * Use the fcsr as a U-mode accesible csr and compare against the custom 'test'
+ * hypervisor csr (currently using vsscratch)
+ */
+#define test_csr(write, initial, mode)								\
+static void test_##write(void)									\
+{												\
+	unsigned long hypervisor_result, reference_result, old_hypervisor;			\
+	unsigned long mask = 0x15;								\
+	asm volatile (										\
+		"csrs	sstatus, %[enable_fp]\n"						\
+		"csrw	fcsr, %[init]\n"							\
+		#write"	zero, fcsr, %[mask]\n"							\
+		"csrr	%[ref_res], fcsr\n"							\
+		: [ref_res] "=&r" (reference_result)						\
+		: [enable_fp] "r" (FP), [mask] #mode(mask), [init] "r" (initial)		\
+		: "memory"									\
+	);											\
+	asm volatile (										\
+		"csrw	%[test_csr], %[init]\n"							\
+		#write"	%[old], %[test_csr], %[mask]\n"						\
+		"csrr	%[hyp_res], %[test_csr]\n"						\
+		: [hyp_res] "=&r" (hypervisor_result), [old] "=&r" (old_hypervisor)		\
+		: [test_csr] "i"(CSR_TEST), [mask] #mode(mask), [init] "r" (initial)		\
+		: "memory"									\
+	);											\
+	/* Check that writing works */								\
+	GUEST_ASSERT_EQ(reference_result, hypervisor_result);					\
+	/* Check that reading works */								\
+	GUEST_ASSERT_EQ(old_hypervisor, initial);						\
+	GUEST_DONE();										\
+}
+
+test_csr(csrrw, 0x0, r)
+test_csr(csrrs, 0x0, r)
+test_csr(csrrc, 0x15, r)
+test_csr(csrrwi, 0x0, i)
+test_csr(csrrsi, 0x0, i)
+test_csr(csrrci, 0x15, i)
+
+static void run(void *guest_code, char *instruction)
+{
+	struct ucall uc;
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+
+	vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+
+	kvm_create_device(vm, KVM_DEV_TYPE_TEST);
+
+	vcpu_run(vcpu);
+
+	TEST_ASSERT(get_ucall(vcpu, &uc) == UCALL_DONE,
+		    "CSR instruction '%s' failed: '%s'", instruction,
+		    uc.buffer);
+
+	kvm_vm_free(vm);
+}
+
+static void check_test_csr_guest(void)
+{
+	unsigned long scause, stvec;
+
+	asm volatile(
+		"la	%[stvec], 1f\n"
+		"csrw	stvec, %[stvec]\n"
+		"csrwi	%[test_csr], 0x0\n"
+		"1:\n"
+		"csrr	%[scause], scause\n"
+		: [scause] "=&r" (scause), [stvec] "=&r" (stvec)
+		: [test_csr] "i" (CSR_TEST)
+	);
+
+	/* An illegal instruction will be generated if CONFIG_RISCV_KVM_TEST_CSR is not enabled. */
+	if (scause == 2)
+		GUEST_FAIL("CONFIG_RISCV_KVM_TEST_CSR not enabled.\n");
+	GUEST_DONE();
+}
+
+static int check_test_csr(void)
+{
+	struct ucall uc;
+	struct kvm_vm *vm;
+	struct kvm_vcpu *vcpu;
+	int success;
+
+	vm = vm_create_with_one_vcpu(&vcpu, check_test_csr_guest);
+
+	/* Skip if CONFIG_KVM_MMIO_TEST not enabled */
+	if (!kvm_create_device(vm, KVM_DEV_TYPE_TEST))
+		exit(KSFT_SKIP);
+
+	vcpu_run(vcpu);
+
+	success = get_ucall(vcpu, &uc) == UCALL_DONE;
+
+	kvm_vm_free(vm);
+
+	return success;
+}
+
+int main(void)
+{
+	/* Skip if CONFIG_RISCV_KVM_TEST_CSR not enabled */
+	if (!check_test_csr())
+		exit(KSFT_SKIP);
+
+	run(test_csrrw, "csrrw");
+	run(test_csrrs, "csrrs");
+	run(test_csrrc, "csrrc");
+	run(test_csrrwi, "csrrwi");
+	run(test_csrrsi, "csrrsi");
+	run(test_csrrci, "csrrci");
+
+	return 0;
+}

-- 
2.54.0