plugins: conditional callbacks

Extend plugins API to support callback called with a given criteria
(evaluated inline).

Added functions:
- qemu_plugin_register_vcpu_tb_exec_cond_cb
- qemu_plugin_register_vcpu_insn_exec_cond_cb

They expect as parameter a condition, a qemu_plugin_u64_t (op1) and an
immediate (op2). Callback is called if op1 |cond| op2 is true.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
Message-Id: <20240502211522.346467-6-pierrick.bouvier@linaro.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
[AJB: fix re-base conflict with tb_is_mem_only()]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20240514174253.694591-8-alex.bennee@linaro.org>

1 files changed, 48 insertions, 0 deletions

diff --git a/accel/tcg/plugin-gen.c b/accel/tcg/plugin-gen.c
index 2cd0e36..14b6603 100644
--- a/accel/tcg/plugin-gen.c
+++ b/accel/tcg/plugin-gen.c
@@ -132,6 +132,51 @@ static TCGv_ptr gen_plugin_u64_ptr(qemu_plugin_u64 entry)
     return ptr;
 }
 
+static TCGCond plugin_cond_to_tcgcond(enum qemu_plugin_cond cond)
+{
+    switch (cond) {
+    case QEMU_PLUGIN_COND_EQ:
+        return TCG_COND_EQ;
+    case QEMU_PLUGIN_COND_NE:
+        return TCG_COND_NE;
+    case QEMU_PLUGIN_COND_LT:
+        return TCG_COND_LTU;
+    case QEMU_PLUGIN_COND_LE:
+        return TCG_COND_LEU;
+    case QEMU_PLUGIN_COND_GT:
+        return TCG_COND_GTU;
+    case QEMU_PLUGIN_COND_GE:
+        return TCG_COND_GEU;
+    default:
+        /* ALWAYS and NEVER conditions should never reach */
+        g_assert_not_reached();
+    }
+}
+
+static void gen_udata_cond_cb(struct qemu_plugin_dyn_cb *cb)
+{
+    TCGv_ptr ptr = gen_plugin_u64_ptr(cb->cond.entry);
+    TCGv_i32 cpu_index = tcg_temp_ebb_new_i32();
+    TCGv_i64 val = tcg_temp_ebb_new_i64();
+    TCGLabel *after_cb = gen_new_label();
+
+    /* Condition should be negated, as calling the cb is the "else" path */
+    TCGCond cond = tcg_invert_cond(plugin_cond_to_tcgcond(cb->cond.cond));
+
+    tcg_gen_ld_i64(val, ptr, 0);
+    tcg_gen_brcondi_i64(cond, val, cb->cond.imm, after_cb);
+    tcg_gen_ld_i32(cpu_index, tcg_env,
+                   -offsetof(ArchCPU, env) + offsetof(CPUState, cpu_index));
+    tcg_gen_call2(cb->cond.f.vcpu_udata, cb->cond.info, NULL,
+                  tcgv_i32_temp(cpu_index),
+                  tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    gen_set_label(after_cb);
+
+    tcg_temp_free_i64(val);
+    tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_ptr(ptr);
+}
+
 static void gen_inline_add_u64_cb(struct qemu_plugin_dyn_cb *cb)
 {
     TCGv_ptr ptr = gen_plugin_u64_ptr(cb->inline_insn.entry);
@@ -177,6 +222,9 @@ static void inject_cb(struct qemu_plugin_dyn_cb *cb)
     case PLUGIN_CB_REGULAR:
         gen_udata_cb(cb);
         break;
+    case PLUGIN_CB_COND:
+        gen_udata_cond_cb(cb);
+        break;
     case PLUGIN_CB_INLINE_ADD_U64:
         gen_inline_add_u64_cb(cb);
         break;