RISC-V: KVM: selftests: Add guest_sbi_probe_extension

Add guest_sbi_probe_extension(), allowing guest code to probe for
SBI extensions. As guest_sbi_probe_extension() needs
SBI_ERR_NOT_SUPPORTED, take the opportunity to bring in all SBI
error codes. We don't bring in all current extension IDs or base
extension function IDs though, even though we need one of each,
because we'd prefer to bring those in as necessary.

Reviewed-by: Anup Patel <[e-mail]>
Reviewed-by: Atish Patra <[e-mail]>
Signed-off-by: Andrew Jones <[e-mail]>
Signed-off-by: Anup Patel <[e-mail]>

tools/testing/selftests/kvm/include/riscv/processor.h

···
 #define SATP_ASID_SHIFT				44
 #define SATP_ASID_MASK				_AC(0xFFFF, UL)
 
+/* SBI return error codes */
+#define SBI_SUCCESS				0
+#define SBI_ERR_FAILURE				-1
+#define SBI_ERR_NOT_SUPPORTED			-2
+#define SBI_ERR_INVALID_PARAM			-3
+#define SBI_ERR_DENIED				-4
+#define SBI_ERR_INVALID_ADDRESS			-5
+#define SBI_ERR_ALREADY_AVAILABLE		-6
+#define SBI_ERR_ALREADY_STARTED			-7
+#define SBI_ERR_ALREADY_STOPPED			-8
+
 #define SBI_EXT_EXPERIMENTAL_START		0x08000000
 #define SBI_EXT_EXPERIMENTAL_END		0x08FFFFFF
 
 #define KVM_RISCV_SELFTESTS_SBI_EXT		SBI_EXT_EXPERIMENTAL_END
 #define KVM_RISCV_SELFTESTS_SBI_UCALL		0
 #define KVM_RISCV_SELFTESTS_SBI_UNEXP		1
+
+enum sbi_ext_id {
+	SBI_EXT_BASE = 0x10,
+};
+
+enum sbi_ext_base_fid {
+	SBI_EXT_BASE_PROBE_EXT = 3,
+};
 
 struct sbiret {
 	long error;
···
 			unsigned long arg1, unsigned long arg2,
 			unsigned long arg3, unsigned long arg4,
 			unsigned long arg5);
+
+bool guest_sbi_probe_extension(int extid, long *out_val);
 
 #endif /* SELFTEST_KVM_PROCESSOR_H */

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

···
 
 	return ret;
 }
+
+bool guest_sbi_probe_extension(int extid, long *out_val)
+{
+	struct sbiret ret;
+
+	ret = sbi_ecall(SBI_EXT_BASE, SBI_EXT_BASE_PROBE_EXT, extid,
+			0, 0, 0, 0, 0);
+
+	__GUEST_ASSERT(!ret.error || ret.error == SBI_ERR_NOT_SUPPORTED,
+		       "ret.error=%ld, ret.value=%ld\n", ret.error, ret.value);
+
+	if (ret.error == SBI_ERR_NOT_SUPPORTED)
+		return false;
+
+	if (out_val)
+		*out_val = ret.value;
+
+	return true;
+}