[Qemu-devel] [RFC v7 16/16] target-arm: aarch64: add atomic instructions

[Alvise Rigo]

Use the new LL/SC runtime helpers to handle the aarch64 atomic instructions
in softmmu_llsc_template.h.

The STXP emulation required a dedicated helper to handle the paired
doubleword case.

Suggested-by: Jani Kokkonen <address@hidden>
Suggested-by: Claudio Fontana <address@hidden>
Signed-off-by: Alvise Rigo <address@hidden>
---
 configure                  |   6 +-
 target-arm/helper-a64.c    |  55 +++++++++++++++++++
 target-arm/helper-a64.h    |   4 ++
 target-arm/op_helper.c     |   8 +++
 target-arm/translate-a64.c | 134 ++++++++++++++++++++++++++++++++++++++++++++-
 5 files changed, 204 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index 915efcc..38121ff 100755
--- a/configure
+++ b/configure
@@ -5873,9 +5873,11 @@ echo "QEMU_CFLAGS+=$cflags" >> $config_target_mak
 # Use tcg LL/SC tcg backend for exclusive instruction is arm/aarch64
 # softmmus targets
 if test "$arm_tcg_use_llsc" = "yes" ; then
-  if test "$target" = "arm-softmmu" ; then
+  case "$target" in
+    arm-softmmu | aarch64-softmmu)
     echo "CONFIG_ARM_USE_LDST_EXCL=y" >> $config_target_mak
-  fi
+    ;;
+  esac
 fi
 done # for target in $targets
 
diff --git a/target-arm/helper-a64.c b/target-arm/helper-a64.c
index c7bfb4d..dcee66f 100644
--- a/target-arm/helper-a64.c
+++ b/target-arm/helper-a64.c
@@ -26,6 +26,7 @@
 #include "qemu/bitops.h"
 #include "internals.h"
 #include "qemu/crc32c.h"
+#include "tcg/tcg.h"
 #include <zlib.h> /* For crc32 */
 
 /* C2.4.7 Multiply and divide */
@@ -443,3 +444,57 @@ uint64_t HELPER(crc32c_64)(uint64_t acc, uint64_t val, 
uint32_t bytes)
     /* Linux crc32c converts the output to one's complement.  */
     return crc32c(acc, buf, bytes) ^ 0xffffffff;
 }
+
+#ifdef CONFIG_ARM_USE_LDST_EXCL
+/* STXP emulation for two 64 bit doublewords. We can't use directly two
+ * stcond_i64 accesses, otherwise the first will conclude the LL/SC pair.
+ * Instead, two normal 64-bit accesses are used and the CPUState is
+ * updated accordingly. */
+target_ulong HELPER(stxp_i128)(CPUArchState *env, target_ulong addr,
+                               uint64_t vall, uint64_t valh,
+                               uint32_t mmu_idx)
+{
+    CPUState *cpu = ENV_GET_CPU(env);
+    TCGMemOpIdx op;
+    target_ulong ret = 0;
+
+    if (!cpu->ll_sc_context) {
+        cpu->excl_succeeded = false;
+        ret = 1;
+        goto out;
+    }
+
+    op = make_memop_idx(MO_BEQ, mmu_idx);
+
+    /* According to section C6.6.191 of ARM ARM DDI 0487A.h, the access has to
+     * be quadword aligned.  For the time being, we do not support paired STXPs
+     * to MMIO memory, this will become trivial when the softmmu will support
+     * 128bit memory accesses. */
+    if (addr & 0xf) {
+        /* TODO: Do unaligned access */
+    }
+
+    /* Setting excl_succeeded to true will make the store exclusive. */
+    cpu->excl_succeeded = true;
+    helper_ret_stq_mmu(env, addr, vall, op, GETRA());
+
+    if (!cpu->excl_succeeded) {
+        ret = 1;
+        goto out;
+    }
+
+    helper_ret_stq_mmu(env, addr + 8, valh, op, GETRA());
+    if (!cpu->excl_succeeded) {
+        ret = 1;
+    } else {
+        cpu->excl_succeeded = false;
+    }
+
+out:
+    /* Unset LL/SC context */
+    cpu->ll_sc_context = false;
+    cpu->excl_protected_range.begin = EXCLUSIVE_RESET_ADDR;
+
+    return ret;
+}
+#endif
diff --git a/target-arm/helper-a64.h b/target-arm/helper-a64.h
index 1d3d10f..c416a83 100644
--- a/target-arm/helper-a64.h
+++ b/target-arm/helper-a64.h
@@ -46,3 +46,7 @@ DEF_HELPER_FLAGS_2(frecpx_f32, TCG_CALL_NO_RWG, f32, f32, ptr)
 DEF_HELPER_FLAGS_2(fcvtx_f64_to_f32, TCG_CALL_NO_RWG, f32, f64, env)
 DEF_HELPER_FLAGS_3(crc32_64, TCG_CALL_NO_RWG_SE, i64, i64, i64, i32)
 DEF_HELPER_FLAGS_3(crc32c_64, TCG_CALL_NO_RWG_SE, i64, i64, i64, i32)
+#ifdef CONFIG_ARM_USE_LDST_EXCL
+/* STXP helper */
+DEF_HELPER_5(stxp_i128, i64, env, i64, i64, i64, i32)
+#endif
diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
index 404c13b..146fc9a 100644
--- a/target-arm/op_helper.c
+++ b/target-arm/op_helper.c
@@ -34,6 +34,14 @@ static void raise_exception(CPUARMState *env, uint32_t excp,
     cs->exception_index = excp;
     env->exception.syndrome = syndrome;
     env->exception.target_el = target_el;
+#ifdef CONFIG_ARM_USE_LDST_EXCL
+    HELPER(atomic_clear)(env);
+    /* If the exception happens in the middle of a LL/SC, we need to clear
+     * excl_succeeded to avoid that the normal store following the exception is
+     * wrongly interpreted as exclusive.
+     * */
+    cs->excl_succeeded = 0;
+#endif
     cpu_loop_exit(cs);
 }
 
diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
index 80f6c20..f34e957 100644
--- a/target-arm/translate-a64.c
+++ b/target-arm/translate-a64.c
@@ -37,8 +37,10 @@
 static TCGv_i64 cpu_X[32];
 static TCGv_i64 cpu_pc;
 
+#if !defined(CONFIG_ARM_USE_LDST_EXCL)
 /* Load/store exclusive handling */
 static TCGv_i64 cpu_exclusive_high;
+#endif
 
 static const char *regnames[] = {
     "x0", "x1", "x2", "x3", "x4", "x5", "x6", "x7",
@@ -94,8 +96,10 @@ void a64_translate_init(void)
                                           regnames[i]);
     }
 
+#if !defined(CONFIG_ARM_USE_LDST_EXCL)
     cpu_exclusive_high = tcg_global_mem_new_i64(TCG_AREG0,
         offsetof(CPUARMState, exclusive_high), "exclusive_high");
+#endif
 }
 
 static inline ARMMMUIdx get_a64_user_mem_index(DisasContext *s)
@@ -1219,7 +1223,11 @@ static void handle_hint(DisasContext *s, uint32_t insn,
 
 static void gen_clrex(DisasContext *s, uint32_t insn)
 {
+#ifndef CONFIG_ARM_USE_LDST_EXCL
     tcg_gen_movi_i64(cpu_exclusive_addr, -1);
+#else
+    gen_helper_atomic_clear(cpu_env);
+#endif
 }
 
 /* CLREX, DSB, DMB, ISB */
@@ -1685,7 +1693,11 @@ static void disas_b_exc_sys(DisasContext *s, uint32_t 
insn)
 }
 
 /*
- * Load/Store exclusive instructions are implemented by remembering
+ * If the softmmu is enabled, the translation of Load/Store exclusive
+ * instructions will rely on the gen_helper_{ldlink,stcond} helpers,
+ * offloading most of the work to the softmmu_llsc_template.h functions.
+ *
+ * Otherwise, instructions are implemented by remembering
  * the value/address loaded, and seeing if these are the same
  * when the store is performed. This is not actually the architecturally
  * mandated semantics, but it works for typical guest code sequences
@@ -1695,6 +1707,66 @@ static void disas_b_exc_sys(DisasContext *s, uint32_t 
insn)
  * this sequence is effectively atomic.  In user emulation mode we
  * throw an exception and handle the atomic operation elsewhere.
  */
+#ifdef CONFIG_ARM_USE_LDST_EXCL
+static void gen_load_exclusive(DisasContext *s, int rt, int rt2,
+                               TCGv_i64 addr, int size, bool is_pair)
+{
+    /* In case @is_pair is set, we have to guarantee that at least the 128 bits
+     * accessed by a Load Exclusive Pair (64-bit variant) are protected. Since
+     * we do not have 128-bit helpers, we split the access in two halves, the
+     * first of them will set the exclusive region to cover at least 128 bits
+     * (this is why aarch64 has a custom cc->cpu_set_excl_protected_range which
+     * covers 128 bits).
+     * */
+    TCGv_i32 mem_idx = tcg_temp_new_i32();
+
+    tcg_gen_movi_i32(mem_idx, get_mem_index(s));
+
+    g_assert(size <= 3);
+
+    if (size < 3) {
+        TCGv_i32 tmp = tcg_temp_new_i32();
+
+        switch (size) {
+        case 0:
+            gen_helper_ldlink_i8(tmp, cpu_env, addr, mem_idx);
+            break;
+        case 1:
+            gen_helper_ldlink_i16(tmp, cpu_env, addr, mem_idx);
+            break;
+        case 2:
+            gen_helper_ldlink_i32(tmp, cpu_env, addr, mem_idx);
+            break;
+        default:
+            abort();
+        }
+
+        TCGv_i64 tmp64 = tcg_temp_new_i64();
+        tcg_gen_ext_i32_i64(tmp64, tmp);
+        tcg_gen_mov_i64(cpu_reg(s, rt), tmp64);
+
+        tcg_temp_free_i32(tmp);
+        tcg_temp_free_i64(tmp64);
+    } else {
+        gen_helper_ldlink_i64(cpu_reg(s, rt), cpu_env, addr, mem_idx);
+    }
+
+    if (is_pair) {
+        TCGMemOp memop = MO_TE + size;
+        TCGv_i64 addr2 = tcg_temp_new_i64();
+        TCGv_i64 hitmp = tcg_temp_new_i64();
+
+        g_assert(size >= 2);
+        tcg_gen_addi_i64(addr2, addr, 1 << size);
+        tcg_gen_qemu_ld_i64(hitmp, addr2, get_mem_index(s), memop);
+        tcg_temp_free_i64(addr2);
+        tcg_gen_mov_i64(cpu_reg(s, rt2), hitmp);
+        tcg_temp_free_i64(hitmp);
+    }
+
+    tcg_temp_free_i32(mem_idx);
+}
+#else
 static void gen_load_exclusive(DisasContext *s, int rt, int rt2,
                                TCGv_i64 addr, int size, bool is_pair)
 {
@@ -1723,6 +1795,7 @@ static void gen_load_exclusive(DisasContext *s, int rt, 
int rt2,
     tcg_temp_free_i64(tmp);
     tcg_gen_mov_i64(cpu_exclusive_addr, addr);
 }
+#endif
 
 #ifdef CONFIG_USER_ONLY
 static void gen_store_exclusive(DisasContext *s, int rd, int rt, int rt2,
@@ -1733,6 +1806,65 @@ static void gen_store_exclusive(DisasContext *s, int rd, 
int rt, int rt2,
                      size | is_pair << 2 | (rd << 4) | (rt << 9) | (rt2 << 
14));
     gen_exception_internal_insn(s, 4, EXCP_STREX);
 }
+#elif defined(CONFIG_ARM_USE_LDST_EXCL)
+static void gen_store_exclusive(DisasContext *s, int rd, int rt, int rt2,
+                                TCGv_i64 addr, int size, int is_pair)
+{
+    /* Don't bother to check if we are actually in exclusive context since the
+     * helpers keep care of it. */
+    TCGv_i32 mem_idx = tcg_temp_new_i32();
+
+    tcg_gen_movi_i32(mem_idx, get_mem_index(s));
+
+    g_assert(size <= 3);
+    if (is_pair) {
+        if (size == 3) {
+            gen_helper_stxp_i128(cpu_reg(s, rd), cpu_env, addr, cpu_reg(s, rt),
+                                 cpu_reg(s, rt2), mem_idx);
+        } else if (size == 2) {
+            /* Paired single word case. After merging the two registers into
+             * one, we use one stcond_i64 to store the value to memory. */
+            TCGv_i64 val = tcg_temp_new_i64();
+            TCGv_i64 valh = tcg_temp_new_i64();
+            tcg_gen_shli_i64(valh, cpu_reg(s, rt2), 32);
+            tcg_gen_and_i64(val, valh, cpu_reg(s, rt));
+            gen_helper_stcond_i64(cpu_reg(s, rd), cpu_env, addr, val, mem_idx);
+            tcg_temp_free_i64(valh);
+            tcg_temp_free_i64(val);
+        } else {
+            abort();
+        }
+    } else {
+        if (size < 3) {
+            TCGv_i32 val = tcg_temp_new_i32();
+
+            tcg_gen_extrl_i64_i32(val, cpu_reg(s, rt));
+
+            switch (size) {
+            case 0:
+                gen_helper_stcond_i8(cpu_reg(s, rd), cpu_env, addr, val,
+                                     mem_idx);
+                break;
+            case 1:
+                gen_helper_stcond_i16(cpu_reg(s, rd), cpu_env, addr, val,
+                                      mem_idx);
+                break;
+            case 2:
+                gen_helper_stcond_i32(cpu_reg(s, rd), cpu_env, addr, val,
+                                      mem_idx);
+                break;
+            default:
+                abort();
+            }
+            tcg_temp_free_i32(val);
+        } else {
+            gen_helper_stcond_i64(cpu_reg(s, rd), cpu_env, addr, cpu_reg(s, 
rt),
+                                  mem_idx);
+        }
+    }
+
+    tcg_temp_free_i32(mem_idx);
+}
 #else
 static void gen_store_exclusive(DisasContext *s, int rd, int rt, int rt2,
                                 TCGv_i64 inaddr, int size, int is_pair)
-- 
2.7.0