On Thu, Oct 21, 2021 at 05:08:09PM -0700, Richard Henderson wrote:
> On 10/21/21 8:09 AM, Ruinland Chuan-Tzu Tsai wrote:
> > riscv_csrrw() will be called by CSR handling helpers, which is the
> > most suitable place for checking wheter a custom CSR is being accessed.
> >
> > If we're touching a custom CSR, invoke the registered handlers.
> >
> > Signed-off-by: Ruinland Chuan-Tzu Tsai <ruinl...@andestech.com>
> > ---
> > target/riscv/cpu.c | 19 +++++++++++++++++
> > target/riscv/cpu.h | 13 +++++++++++-
> > target/riscv/csr.c | 38 +++++++++++++++++++++++++++-------
> > target/riscv/custom_csr_defs.h | 7 +++++++
> > 4 files changed, 68 insertions(+), 9 deletions(-)
> > create mode 100644 target/riscv/custom_csr_defs.h
> >
> > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
> > index 0c93b7edd7..a72fd32f01 100644
> > --- a/target/riscv/cpu.c
> > +++ b/target/riscv/cpu.c
> > @@ -34,6 +34,9 @@
> > static const char riscv_exts[26] = "IEMAFDQCLBJTPVNSUHKORWXYZG";
> > +GHashTable *custom_csr_map = NULL;
>
> Leftover from a previous revision?
By default there's no custom_csr_map (pointing to NULL) and thus only the
custom CSR equipped CPU models will need to initialize that. Standard CPU will
pass the check of custom_csr_map in riscv_csrrw() by default.
>
> > +#include "custom_csr_defs.h"
>
> I think that the few declarations that are required can just go in
> internals.h.
Wilco.
>
> > +
> > const char * const riscv_int_regnames[] = {
> > "x0/zero", "x1/ra", "x2/sp", "x3/gp", "x4/tp", "x5/t0", "x6/t1",
> > "x7/t2", "x8/s0", "x9/s1", "x10/a0", "x11/a1", "x12/a2", "x13/a3",
> > @@ -149,6 +152,22 @@ static void set_resetvec(CPURISCVState *env,
> > target_ulong resetvec)
> > #endif
> > }
> > +static void setup_custom_csr(CPURISCVState *env,
> > + riscv_custom_csr_operations csr_map_struct[])
>
> Why is this static? Surely it needs to be called from csr_andes.c, etc?
> Oh, I see that in the next patch you call this directly from ax25_cpu_init.
>
> I think the split of declarations is less than ideal. See below.
>
> > +{
> > + int i;
> > + env->custom_csr_map = g_hash_table_new(g_direct_hash, g_direct_equal);
> > + for (i = 0; i < MAX_CUSTOM_CSR_NUM; i++) {
>
> Having a hard maximum seems a mistake. You should pass in the array size...
>
> > + if (csr_map_struct[i].csrno != 0) {
> > + g_hash_table_insert(env->custom_csr_map,
> > + GINT_TO_POINTER(csr_map_struct[i].csrno),
> > + &csr_map_struct[i].csr_opset);
> > + } else {
> > + break;
> > + }
>
> ... which would also allow you to remove the terminator in the data, and the
> check here.
Wilco.
>
> > @@ -245,6 +245,11 @@ struct CPURISCVState {
> > /* Fields from here on are preserved across CPU reset. */
> > QEMUTimer *timer; /* Internal timer */
> > +
> > + /* Custom CSR opset table per hart */
> > + GHashTable *custom_csr_map;
>
> I think placing this in the CPURISCVState is incorrect. A much better place
> would be on the RISCVCPUClass, so that there is exactly one copy of this per
> cpu type, i.e. all A25/AX25 cpus would share the same table.
>
> You would of course need to hook class_init, which the current definition of
> DEFINE_CPU does not allow. But that's easy to fix.
>
> > + /* Custom CSR value holder per hart */
> > + void *custom_csr_val;
> > };
>
> Value singular? Anyhow, I think that it's a mistake trying to hide the
> value structure in another file. It complicates allocation of the
> CPURISCVState, and you have no mechanism by which to migrate the csr values.
What I'm trying to do here is to provide a hook for CSR value storage and let
it being set during CPU initilization. We have heterogeneous harts which
have different sets of CSRs.
>
> I think you should simply place your structure here in CPURISCVState.
>
> > +static gpointer find_custom_csr(CPURISCVState *env, int csrno)
> > +{
> > + gpointer ret;
> > + ret = g_hash_table_lookup(env->custom_csr_map, GINT_TO_POINTER(csrno));
> > + return ret;
> > +}
>
> Fix the return type; the csr is not gpointer.
> It would be better to put the map not null test here.
>
> I think it would be even better to name this find_csr,
> and include the normal index of csr_ops[] if the map
> test fails.
Wilco.
>
> > @@ -1449,26 +1458,39 @@ RISCVException riscv_csrrw(CPURISCVState *env, int
> > csrno,
> > return RISCV_EXCP_ILLEGAL_INST;
> > }
> > + /* try to handle_custom_csr */
> > + if (unlikely(env->custom_csr_map != NULL)) {
> > + riscv_csr_operations *custom_csr_opset = (riscv_csr_operations *)
> > + find_custom_csr(env, csrno);
> > + if (custom_csr_opset != NULL) {
> > + csr_op = custom_csr_opset;
> > + } else {
> > + csr_op = &csr_ops[csrno];
> > + }
> > + } else {
> > + csr_op = &csr_ops[csrno];
> > + }
>
> As Alistair noted, run checkpatch.pl to find all of these indentation errors.
>
> That said, a better structure here would be
>
> csr_op = find_csr(env, csrno);
> if (csr_op == NULL) {
> return RISCV_EXCP_ILLEGAL_INST;
> }
Thanks for the tips. Wilco.
>
>
> r~
Cordially yours,
Ruinland
