RISC-V: Allow both Zmmul and M

We got to talking about how Zmmul and M interact with each other
https://github.com/riscv/riscv-isa-manual/issues/869 , and it turns out
that QEMU's behavior is slightly wrong: having Zmmul and M is a legal
combination, it just means that the multiplication instructions are
supported even when M is disabled at runtime via misa.

This just stops overriding M from Zmmul, with that the other checks for
the multiplication instructions work as per the ISA.

Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20220714180033.22385-1-palmer@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 1bb3973806d2d56258ee64acf5d498c9f27c780b..ac6f82ebd006d9dc19bfa2808e4f7d018b895686 100644 (file)
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -619,11 +619,6 @@ static void riscv_cpu_realize(DeviceState *dev, Error **errp)
             cpu->cfg.ext_ifencei = true;
         }
 
-        if (cpu->cfg.ext_m && cpu->cfg.ext_zmmul) {
-            warn_report("Zmmul will override M");
-            cpu->cfg.ext_m = false;
-        }
-
         if (cpu->cfg.ext_i && cpu->cfg.ext_e) {
             error_setg(errp,
                        "I and E extensions are incompatible");