[RFC PATCH v5 1/2] target/riscv: Add RISC-V CSR qtest support

[Ivan Klokov <ivan.klokov@syntacore.com>]

The RISC-V architecture supports the creation of custom
CSR-mapped devices. It would be convenient to test them in the same way
as MMIO-mapped devices. To do this, a new call has been added
to read/write CSR registers.

Signed-off-by: Ivan Klokov <ivan.klokov@syntacore.com>
---
 hw/riscv/riscv_hart.c  | 65 ++++++++++++++++++++++++++++++++++++++++++
 tests/qtest/libqtest.c | 27 ++++++++++++++++++
 tests/qtest/libqtest.h | 14 +++++++++
 3 files changed, 106 insertions(+)

diff --git a/hw/riscv/riscv_hart.c b/hw/riscv/riscv_hart.c
index 613ea2aaa0..e65a1a28a1 100644
--- a/hw/riscv/riscv_hart.c
+++ b/hw/riscv/riscv_hart.c
@@ -21,6 +21,8 @@
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "qemu/module.h"
+#include "qemu/cutils.h"
+#include "sysemu/qtest.h"
 #include "sysemu/reset.h"
 #include "hw/sysbus.h"
 #include "target/riscv/cpu.h"
@@ -42,6 +44,66 @@ static void riscv_harts_cpu_reset(void *opaque)
     cpu_reset(CPU(cpu));
 }
 
+#ifndef CONFIG_USER_ONLY
+static uint64_t csr_call(char *cmd, uint64_t cpu_num, int csrno,
+                                uint64_t *val)
+{
+    RISCVCPU *cpu = RISCV_CPU(cpu_by_arch_id(cpu_num));
+    CPURISCVState *env = &cpu->env;
+
+    int ret = RISCV_EXCP_NONE;
+    if (strcmp(cmd, "get_csr") == 0) {
+        ret = riscv_csrr(env, csrno, (target_ulong *)val);
+    } else if (strcmp(cmd, "set_csr") == 0) {
+        ret = riscv_csrrw(env, csrno, NULL, *(target_ulong *)val, MAKE_64BIT_MASK(0, TARGET_LONG_BITS));
+    }
+
+    if (ret == RISCV_EXCP_NONE) {
+        ret = 0;
+    } else {
+        g_assert_not_reached();
+    }
+
+    return ret;
+}
+
+static bool csr_qtest_callback(CharBackend *chr, gchar **words)
+{
+    if (strcmp(words[0], "csr") == 0) {
+
+        uint64_t res, cpu;
+
+        uint64_t val;
+        int rc, csr;
+
+        rc = qemu_strtou64(words[2], NULL, 0, &cpu);
+        g_assert(rc == 0);
+        rc = qemu_strtoi(words[3], NULL, 0, &csr);
+        g_assert(rc == 0);
+        rc = qemu_strtou64(words[4], NULL, 0, &val);
+        g_assert(rc == 0);
+        res = csr_call(words[1], cpu, csr, &val);
+
+        qtest_send_prefix(chr);
+        qtest_sendf(chr, "OK %"PRIx64" "TARGET_FMT_lx"\n", res, (target_ulong)val);
+
+        return true;
+    }
+
+    return false;
+}
+
+static void riscv_cpu_register_csr_qtest_callback(void)
+{
+    static gsize reinit_done;
+    if (g_once_init_enter(&reinit_done)) {
+        qtest_set_command_cb(csr_qtest_callback);
+
+        g_once_init_leave(&reinit_done, 1);
+    }
+}
+#endif
+
 static bool riscv_hart_realize(RISCVHartArrayState *s, int idx,
                                char *cpu_type, Error **errp)
 {
@@ -49,6 +111,9 @@ static bool riscv_hart_realize(RISCVHartArrayState *s, int idx,
     qdev_prop_set_uint64(DEVICE(&s->harts[idx]), "resetvec", s->resetvec);
     s->harts[idx].env.mhartid = s->hartid_base + idx;
     qemu_register_reset(riscv_harts_cpu_reset, &s->harts[idx]);
+#ifndef CONFIG_USER_ONLY
+    riscv_cpu_register_csr_qtest_callback();
+#endif
     return qdev_realize(DEVICE(&s->harts[idx]), NULL, errp);
 }
 
diff --git a/tests/qtest/libqtest.c b/tests/qtest/libqtest.c
index 9d07de1fbd..661f7f0e84 100644
--- a/tests/qtest/libqtest.c
+++ b/tests/qtest/libqtest.c
@@ -1202,6 +1202,33 @@ uint64_t qtest_rtas_call(QTestState *s, const char *name,
     return 0;
 }
 
+static void qtest_rsp_csr(QTestState *s, uint64_t *val)
+{
+    gchar **args;
+    uint64_t ret;
+    int rc;
+
+    args = qtest_rsp_args(s, 3);
+
+    rc = qemu_strtou64(args[1], NULL, 16, &ret);
+    g_assert(rc == 0);
+    rc = qemu_strtou64(args[2], NULL, 16, val);
+    g_assert(rc == 0);
+
+    g_strfreev(args);
+}
+
+uint64_t qtest_csr_call(QTestState *s, const char *name,
+                         uint64_t cpu, int csr,
+                         uint64_t *val)
+{
+    qtest_sendf(s, "csr %s 0x%"PRIx64" %d 0x%"PRIx64"\n",
+                    name, cpu, csr, *val);
+
+    qtest_rsp_csr(s, val);
+    return 0;
+}
+
 void qtest_add_func(const char *str, void (*fn)(void))
 {
     gchar *path = g_strdup_printf("/%s/%s", qtest_get_arch(), str);
diff --git a/tests/qtest/libqtest.h b/tests/qtest/libqtest.h
index beb96b18eb..b516a16bd4 100644
--- a/tests/qtest/libqtest.h
+++ b/tests/qtest/libqtest.h
@@ -575,6 +575,20 @@ uint64_t qtest_rtas_call(QTestState *s, const char *name,
                          uint32_t nargs, uint64_t args,
                          uint32_t nret, uint64_t ret);
 
+/**
+ * qtest_csr_call:
+ * @s: #QTestState instance to operate on.
+ * @name: name of the command to call.
+ * @cpu: hart number.
+ * @csr: CSR number.
+ * @val: Value for reading/writing.
+ *
+ * Call an RISC-V CSR read/write function
+ */
+uint64_t qtest_csr_call(QTestState *s, const char *name,
+                         uint64_t cpu, int csr,
+                         unsigned long *val);
+
 /**
  * qtest_bufread:
  * @s: #QTestState instance to operate on.
-- 
2.34.1