target/riscv: rvv: Add option 'rvv_ta_all_1s' to enable optional tail agnostic behavior

According to v-spec, tail agnostic behavior can be either kept as
undisturbed or set elements' bits to all 1s. To distinguish the
difference of tail policies, QEMU should be able to simulate the tail
agnostic behavior as "set tail elements' bits to all 1s".

There are multiple possibility for agnostic elements according to
v-spec. The main intent of this patch-set tries to add option that
can distinguish between tail policies. Setting agnostic elements to
all 1s allows QEMU to express this.

This commit adds option 'rvv_ta_all_1s' is added to enable the
behavior, it is default as disabled.

Signed-off-by: eop Chen <eop.chen@sifive.com>
Reviewed-by: Frank Chang <frank.chang@sifive.com>
Reviewed-by: Weiwei Li <liweiwei@iscas.ac.cn>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <165449614532.19704.7000832880482980398-16@git.sr.ht>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 0497af45cc950b0ceef1fac04b5115c120bd9a0d..e5aa1e9c1bf48882c62b380c3868b71ea9237771 100644 (file)
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -918,6 +918,8 @@ static Property riscv_cpu_properties[] = {
     DEFINE_PROP_UINT64("resetvec", RISCVCPU, cfg.resetvec, DEFAULT_RSTVEC),
 
     DEFINE_PROP_BOOL("short-isa-string", RISCVCPU, cfg.short_isa_string, false),
+
+    DEFINE_PROP_BOOL("rvv_ta_all_1s", RISCVCPU, cfg.rvv_ta_all_1s, false),
     DEFINE_PROP_END_OF_LIST(),
 };