On Thu, 2024-01-11 at 11:53 -0300, Daniel Henrique Barboza wrote: > > > On 1/11/24 10:02, Andrew Jones wrote: > > On Wed, Jan 10, 2024 at 03:32:21PM -0300, Daniel Henrique Barboza > > wrote: > > > > > > > > > On 1/9/24 14:07, Rob Bradford wrote: > > > > Signed-off-by: Rob Bradford <rbradf...@rivosinc.com> > > > > --- > > > > target/riscv/tcg/tcg-cpu.c | 3 ++- > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg- > > > > cpu.c > > > > index f10871d352..9705daec93 100644 > > > > --- a/target/riscv/tcg/tcg-cpu.c > > > > +++ b/target/riscv/tcg/tcg-cpu.c > > > > @@ -999,7 +999,8 @@ static void > > > > riscv_init_max_cpu_extensions(Object *obj) > > > > const RISCVCPUMultiExtConfig *prop; > > > > /* Enable RVG, RVJ and RVV that are disabled by default > > > > */ > > > > - riscv_cpu_set_misa(env, env->misa_mxl, env->misa_ext | RVG > > > > | RVJ | RVV); > > > > + riscv_cpu_set_misa(env, env->misa_mxl, > > > > + env->misa_ext | RVG | RVJ | RVV | RVB); > > > > > > I'm aware that we decided a while ago the 'max' CPU could only > > > have non-vendor and > > > non-experimental extensions enabled. RVB is experimental, so in > > > theory we shouldn't > > > enable it. > > > > > > But RVB is an alias for zba, zbb and zbs, extensions that the > > > 'max' CPU is already > > > enabling. In this case I think it's sensible to enable RVB here > > > since it would > > > just > > > > > > reflect stuff that it's already happening. > > > > It's also setting the B bit in misa, which, until this spec is at > > least > > frozen, is a reserved bit and reserved bits "must return zero when > > read". > > This is a side effect that I wasn't aware of. > > Rob, given that the 'max' CPU already has the zb* extensions enabled, > is there any > other gain in enabling RVB in this CPU? If there isn't I'd rather > leave this one > out for now. >
It seems completely reasonable to me to drop it for now. Thanks for all the feedback, Rob > > Thanks, > > Daniel > > > > > > I don't want to stand in the way of progress and it seems 99.9% > > likely > > that the spec will be frozen and ratified, but, if we want to stick > > to > > our policies (which we should document), then even the 'max' cpu > > type > > should require x-b be added to the command line if it wants the B > > bit > > set in misa. > > > > Thanks, > > drew
