On Wed, Jul 27, 2022 at 9:24 AM Richard Henderson
<richard.hender...@linaro.org> wrote:
>
> On 7/26/22 20:25, Anup Patel wrote:
> > We should call decode_save_opc() for every decoded instruction
> > because generating transformed instruction upon guest page faults
> > expects opcode to be available. Without this, hypervisor sees
> > transformed instruction as zero in htinst CSR for guest MMIO
> > emulation which makes MMIO emulation in hypervisor slow and
> > also breaks nested virtualization.
>
> Then just add decode_save_opc to load/store insns, not everything including
> plain
> arithmetic...
We will have to add for float load/store, atomics, and HLV/HSV as
well. Basically we end-up adding for everything except integer and
float arithmetic.
I see that decode_save_opc() only saves opcode in an array
through tcg_set_insn_start_param(). Which brings me to the
question about how much are we saving by distributing
decode_save_opc() calls ?
If we distribute decode_save_opc() calls then the code becomes
fragile for future changes and we will miss adding decode_save_opc()
for some new extensions.
Regards,
Anup
>
>
> r~
>
>
> >
> > Fixes: a9814e3e08d2 ("target/riscv: Minimize the calls to decode_save_opc")
> > Signed-off-by: Anup Patel <apa...@ventanamicro.com>
> > ---
> > target/riscv/insn_trans/trans_privileged.c.inc | 4 ----
> > target/riscv/insn_trans/trans_rvh.c.inc | 2 --
> > target/riscv/insn_trans/trans_rvi.c.inc | 2 --
> > target/riscv/translate.c | 10 ++++------
> > 4 files changed, 4 insertions(+), 14 deletions(-)
> >
> > diff --git a/target/riscv/insn_trans/trans_privileged.c.inc
> > b/target/riscv/insn_trans/trans_privileged.c.inc
> > index 46f96ad74d..53613682e8 100644
> > --- a/target/riscv/insn_trans/trans_privileged.c.inc
> > +++ b/target/riscv/insn_trans/trans_privileged.c.inc
> > @@ -75,7 +75,6 @@ static bool trans_sret(DisasContext *ctx, arg_sret *a)
> > {
> > #ifndef CONFIG_USER_ONLY
> > if (has_ext(ctx, RVS)) {
> > - decode_save_opc(ctx);
> > gen_helper_sret(cpu_pc, cpu_env);
> > tcg_gen_exit_tb(NULL, 0); /* no chaining */
> > ctx->base.is_jmp = DISAS_NORETURN;
> > @@ -91,7 +90,6 @@ static bool trans_sret(DisasContext *ctx, arg_sret *a)
> > static bool trans_mret(DisasContext *ctx, arg_mret *a)
> > {
> > #ifndef CONFIG_USER_ONLY
> > - decode_save_opc(ctx);
> > gen_helper_mret(cpu_pc, cpu_env);
> > tcg_gen_exit_tb(NULL, 0); /* no chaining */
> > ctx->base.is_jmp = DISAS_NORETURN;
> > @@ -104,7 +102,6 @@ static bool trans_mret(DisasContext *ctx, arg_mret *a)
> > static bool trans_wfi(DisasContext *ctx, arg_wfi *a)
> > {
> > #ifndef CONFIG_USER_ONLY
> > - decode_save_opc(ctx);
> > gen_set_pc_imm(ctx, ctx->pc_succ_insn);
> > gen_helper_wfi(cpu_env);
> > return true;
> > @@ -116,7 +113,6 @@ static bool trans_wfi(DisasContext *ctx, arg_wfi *a)
> > static bool trans_sfence_vma(DisasContext *ctx, arg_sfence_vma *a)
> > {
> > #ifndef CONFIG_USER_ONLY
> > - decode_save_opc(ctx);
> > gen_helper_tlb_flush(cpu_env);
> > return true;
> > #endif
> > diff --git a/target/riscv/insn_trans/trans_rvh.c.inc
> > b/target/riscv/insn_trans/trans_rvh.c.inc
> > index 4f8aecddc7..cebcb3f8f6 100644
> > --- a/target/riscv/insn_trans/trans_rvh.c.inc
> > +++ b/target/riscv/insn_trans/trans_rvh.c.inc
> > @@ -169,7 +169,6 @@ static bool trans_hfence_gvma(DisasContext *ctx,
> > arg_sfence_vma *a)
> > {
> > REQUIRE_EXT(ctx, RVH);
> > #ifndef CONFIG_USER_ONLY
> > - decode_save_opc(ctx);
> > gen_helper_hyp_gvma_tlb_flush(cpu_env);
> > return true;
> > #endif
> > @@ -180,7 +179,6 @@ static bool trans_hfence_vvma(DisasContext *ctx,
> > arg_sfence_vma *a)
> > {
> > REQUIRE_EXT(ctx, RVH);
> > #ifndef CONFIG_USER_ONLY
> > - decode_save_opc(ctx);
> > gen_helper_hyp_tlb_flush(cpu_env);
> > return true;
> > #endif
> > diff --git a/target/riscv/insn_trans/trans_rvi.c.inc
> > b/target/riscv/insn_trans/trans_rvi.c.inc
> > index c49dbec0eb..1f318ffbef 100644
> > --- a/target/riscv/insn_trans/trans_rvi.c.inc
> > +++ b/target/riscv/insn_trans/trans_rvi.c.inc
> > @@ -834,8 +834,6 @@ static bool trans_fence_i(DisasContext *ctx,
> > arg_fence_i *a)
> >
> > static bool do_csr_post(DisasContext *ctx)
> > {
> > - /* The helper may raise ILLEGAL_INSN -- record binv for unwind. */
> > - decode_save_opc(ctx);
> > /* We may have changed important cpu state -- exit to main loop. */
> > gen_set_pc_imm(ctx, ctx->pc_succ_insn);
> > tcg_gen_exit_tb(NULL, 0);
> > diff --git a/target/riscv/translate.c b/target/riscv/translate.c
> > index a79d0cd95b..5425d19846 100644
> > --- a/target/riscv/translate.c
> > +++ b/target/riscv/translate.c
> > @@ -207,10 +207,10 @@ static void gen_check_nanbox_s(TCGv_i64 out, TCGv_i64
> > in)
> > tcg_gen_movcond_i64(TCG_COND_GEU, out, in, t_max, in, t_nan);
> > }
> >
> > -static void decode_save_opc(DisasContext *ctx)
> > +static void decode_save_opc(DisasContext *ctx, target_ulong opc)
> > {
> > assert(ctx->insn_start != NULL);
> > - tcg_set_insn_start_param(ctx->insn_start, 1, ctx->opcode);
> > + tcg_set_insn_start_param(ctx->insn_start, 1, opc);
> > ctx->insn_start = NULL;
> > }
> >
> > @@ -240,8 +240,6 @@ static void generate_exception(DisasContext *ctx, int
> > excp)
> >
> > static void gen_exception_illegal(DisasContext *ctx)
> > {
> > - tcg_gen_st_i32(tcg_constant_i32(ctx->opcode), cpu_env,
> > - offsetof(CPURISCVState, bins));
> > generate_exception(ctx, RISCV_EXCP_ILLEGAL_INST);
> > }
> >
> > @@ -643,8 +641,6 @@ static void gen_set_rm(DisasContext *ctx, int rm)
> > return;
> > }
> >
> > - /* The helper may raise ILLEGAL_INSN -- record binv for unwind. */
> > - decode_save_opc(ctx);
> > gen_helper_set_rounding_mode(cpu_env, tcg_constant_i32(rm));
> > }
> >
> > @@ -1055,6 +1051,7 @@ static void decode_opc(CPURISCVState *env,
> > DisasContext *ctx, uint16_t opcode)
> >
> > /* Check for compressed insn */
> > if (extract16(opcode, 0, 2) != 3) {
> > + decode_save_opc(ctx, opcode);
> > if (!has_ext(ctx, RVC)) {
> > gen_exception_illegal(ctx);
> > } else {
> > @@ -1071,6 +1068,7 @@ static void decode_opc(CPURISCVState *env,
> > DisasContext *ctx, uint16_t opcode)
> > ctx->base.pc_next + 2));
> > ctx->opcode = opcode32;
> > ctx->pc_succ_insn = ctx->base.pc_next + 4;
> > + decode_save_opc(ctx, opcode32);
> >
> > for (size_t i = 0; i < ARRAY_SIZE(decoders); ++i) {
> > if (decoders[i].guard_func(ctx) &&
>
