RISC-V: Clear load reservations on context switch and SC

This prevents a load reservation from being placed in one context/process,
then being used in another, resulting in an SC succeeding incorrectly and
breaking atomics.

Signed-off-by: Joel Sing <joel@sing.id.au>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/target/riscv/insn_trans/trans_rva.inc.c b/target/riscv/insn_trans/trans_rva.inc.c
index f6dbbc065e..fadd88849e 100644
--- a/target/riscv/insn_trans/trans_rva.inc.c
+++ b/target/riscv/insn_trans/trans_rva.inc.c
@@ -61,7 +61,7 @@ static inline bool gen_sc(DisasContext *ctx, arg_atomic *a, TCGMemOp mop)
 
     gen_set_label(l1);
     /*
-     * Address comparion failure.  However, we still need to
+     * Address comparison failure.  However, we still need to
      * provide the memory barrier implied by AQ/RL.
      */
     tcg_gen_mb(TCG_MO_ALL + a->aq * TCG_BAR_LDAQ + a->rl * TCG_BAR_STRL);
@@ -69,6 +69,12 @@ static inline bool gen_sc(DisasContext *ctx, arg_atomic *a, TCGMemOp mop)
     gen_set_gpr(a->rd, dat);
 
     gen_set_label(l2);
+    /*
+     * Clear the load reservation, since an SC must fail if there is
+     * an SC to any address, in between an LR and SC pair.
+     */
+    tcg_gen_movi_tl(load_res, -1);
+
     tcg_temp_free(dat);
     tcg_temp_free(src1);
     tcg_temp_free(src2);