High level description: The 68881/68882 FPUs require fsave/frestore instructions to read/write state frames. QEMU only fully implemented this for the 68040. The Sun-3 uses a 68881 FPU, and the boot ROM executes `fsave` to probe FPU presence. This patch adds basic 68881 FPU state frame handling (NULL frame) to accurately simulate an idle FPU state.
Impact on existing functionality: Fixes FPU detection for 68881/68882 across all M68k boards without affecting 68040 specific state logic. Context: This patch was originally submitted as part of the monolithic Sun-3 Machine Emulation series (https://patchew.org/QEMU/[email protected]/) and has been split into atomic components. --- target/m68k/translate.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/target/m68k/translate.c b/target/m68k/translate.c index 138c89d3e5..bdf619883c 100644 --- a/target/m68k/translate.c +++ b/target/m68k/translate.c @@ -5364,11 +5364,19 @@ DISAS_INSN(frestore) gen_exception(s, s->base.pc_next, EXCP_PRIVILEGE); return; } - if (m68k_feature(s->env, M68K_FEATURE_M68040)) { + if (m68k_feature(s->env, M68K_FEATURE_M68040) || + m68k_feature(s->env, M68K_FEATURE_FPU)) { SRC_EA(env, addr, OS_LONG, 0, NULL); - /* FIXME: check the state frame */ + if (m68k_feature(s->env, M68K_FEATURE_M68040)) { + /* FIXME: check the state frame */ + } else { + /* + * 68881/68882 FRESTORE: read the state frame + * (NULL frame is 4 bytes) + */ + } } else { - disas_undef(env, s, insn); + disas_undef_fpu(env, s, insn); } } @@ -5383,8 +5391,12 @@ DISAS_INSN(fsave) /* always write IDLE */ TCGv idle = tcg_constant_i32(0x41000000); DEST_EA(env, insn, OS_LONG, idle, NULL); + } else if (m68k_feature(s->env, M68K_FEATURE_FPU)) { + /* 68881/68882 FSAVE: always write NULL frame */ + TCGv null_frame = tcg_constant_i32(0x00000000); + DEST_EA(env, insn, OS_LONG, null_frame, NULL); } else { - disas_undef(env, s, insn); + disas_undef_fpu(env, s, insn); } } #endif -- 2.50.1 (Apple Git-155)
