An Event-Based Branch (EBB) allows applications to change the NIA when a event-based exception occurs. Event-based exceptions are enabled by setting the Branch Event Status and Control Register (BESCR). If the event-based exception is enabled when the exception occurs, an EBB happens.
The following operations happens during an EBB: - Global Enable (GE) bit of BESCR is set to 0; - bits 0-61 of the Event-Based Branch Return Register (EBBRR) are set to the the effective address of the NIA that would have executed if the EBB didn't happen; - Instruction fetch and execution will continue in the effective address contained in the Event-Based Branch Handler Register (EBBHR). The EBB Handler will process the event and then execute the Return From Event-Based Branch (rfebb) instruction. rfebb sets BESCR_GE and then redirects execution to the address pointed in EBBRR. This process is described in the PowerISA v3.1, Book II, Chapter 6 [1]. This patch implements the rfebb instruction. Descriptions of all relevant BESCR bits are also added - this patch is only using BESCR_GE, but the next patches will use the remaining bits. [1] https://wiki.raptorcs.com/w/images/f/f5/PowerISA_public.v3.1.pdf Reviewed-by: Matheus Ferst <matheus.fe...@eldorado.org.br> Signed-off-by: Daniel Henrique Barboza <danielhb...@gmail.com> --- target/ppc/cpu.h | 13 ++++++++++ target/ppc/excp_helper.c | 31 ++++++++++++++++++++++++ target/ppc/helper.h | 1 + target/ppc/insn32.decode | 5 ++++ target/ppc/translate.c | 2 ++ target/ppc/translate/branch-impl.c.inc | 33 ++++++++++++++++++++++++++ 6 files changed, 85 insertions(+) create mode 100644 target/ppc/translate/branch-impl.c.inc diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h index a1957c5e7a..bd807aa7ea 100644 --- a/target/ppc/cpu.h +++ b/target/ppc/cpu.h @@ -392,6 +392,19 @@ typedef enum { /* PMU uses CTRL_RUN to sample PM_RUN_INST_CMPL */ #define CTRL_RUN PPC_BIT(63) +/* EBB/BESCR bits */ +/* Global Enable */ +#define BESCR_GE PPC_BIT(0) +/* External Event-based Exception Enable */ +#define BESCR_EE PPC_BIT(30) +/* Performance Monitor Event-based Exception Enable */ +#define BESCR_PME PPC_BIT(31) +/* External Event-based Exception Occurred */ +#define BESCR_EEO PPC_BIT(62) +/* Performance Monitor Event-based Exception Occurred */ +#define BESCR_PMEO PPC_BIT(63) +#define BESCR_INVALID PPC_BITMASK(32, 33) + /* LPCR bits */ #define LPCR_VPM0 PPC_BIT(0) #define LPCR_VPM1 PPC_BIT(1) diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c index 17607adbe4..7ead32279c 100644 --- a/target/ppc/excp_helper.c +++ b/target/ppc/excp_helper.c @@ -1250,6 +1250,37 @@ void helper_hrfid(CPUPPCState *env) } #endif +#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) +void helper_rfebb(CPUPPCState *env, target_ulong s) +{ + target_ulong msr = env->msr; + + /* + * Handling of BESCR bits 32:33 according to PowerISA v3.1: + * + * "If BESCR 32:33 != 0b00 the instruction is treated as if + * the instruction form were invalid." + */ + if (env->spr[SPR_BESCR] & BESCR_INVALID) { + raise_exception_err(env, POWERPC_EXCP_PROGRAM, + POWERPC_EXCP_INVAL | POWERPC_EXCP_INVAL_INVAL); + } + + env->nip = env->spr[SPR_EBBRR]; + + /* Switching to 32-bit ? Crop the nip */ + if (!msr_is_64bit(env, msr)) { + env->nip = (uint32_t)env->spr[SPR_EBBRR]; + } + + if (s) { + env->spr[SPR_BESCR] |= BESCR_GE; + } else { + env->spr[SPR_BESCR] &= ~BESCR_GE; + } +} +#endif + /*****************************************************************************/ /* Embedded PowerPC specific helpers */ void helper_40x_rfci(CPUPPCState *env) diff --git a/target/ppc/helper.h b/target/ppc/helper.h index ce05470fd4..ba69b57163 100644 --- a/target/ppc/helper.h +++ b/target/ppc/helper.h @@ -18,6 +18,7 @@ DEF_HELPER_2(pminsn, void, env, i32) DEF_HELPER_1(rfid, void, env) DEF_HELPER_1(rfscv, void, env) DEF_HELPER_1(hrfid, void, env) +DEF_HELPER_2(rfebb, void, env, tl) DEF_HELPER_2(store_lpcr, void, env, tl) DEF_HELPER_2(store_pcr, void, env, tl) DEF_HELPER_2(store_mmcr0, void, env, tl) diff --git a/target/ppc/insn32.decode b/target/ppc/insn32.decode index e135b8aba4..6cad783dde 100644 --- a/target/ppc/insn32.decode +++ b/target/ppc/insn32.decode @@ -427,3 +427,8 @@ XXSPLTW 111100 ..... ---.. ..... 010100100 . . @XX2 ## VSX Vector Load Special Value Instruction LXVKQ 111100 ..... 11111 ..... 0101101000 . @X_uim5 + +### rfebb +&XL_s s:uint8_t +@XL_s ......-------------- s:1 .......... - &XL_s +RFEBB 010011-------------- . 0010010010 - @XL_s diff --git a/target/ppc/translate.c b/target/ppc/translate.c index d0e361a9d1..d643a83a51 100644 --- a/target/ppc/translate.c +++ b/target/ppc/translate.c @@ -7467,6 +7467,8 @@ static bool resolve_PLS_D(DisasContext *ctx, arg_D *d, arg_PLS_D *a) #include "translate/spe-impl.c.inc" +#include "translate/branch-impl.c.inc" + /* Handles lfdp, lxsd, lxssp */ static void gen_dform39(DisasContext *ctx) { diff --git a/target/ppc/translate/branch-impl.c.inc b/target/ppc/translate/branch-impl.c.inc new file mode 100644 index 0000000000..29cfa11854 --- /dev/null +++ b/target/ppc/translate/branch-impl.c.inc @@ -0,0 +1,33 @@ +/* + * Power ISA decode for branch instructions + * + * Copyright IBM Corp. 2021 + * + * Authors: + * Daniel Henrique Barboza <danielhb...@gmail.com> + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) + +static bool trans_RFEBB(DisasContext *ctx, arg_XL_s *arg) +{ + REQUIRE_INSNS_FLAGS2(ctx, ISA207S); + + gen_icount_io_start(ctx); + gen_update_cfar(ctx, ctx->cia); + gen_helper_rfebb(cpu_env, cpu_gpr[arg->s]); + + ctx->base.is_jmp = DISAS_CHAIN; + + return true; +} +#else +static bool trans_RFEBB(DisasContext *ctx, arg_XL_s *arg) +{ + gen_invalid(ctx); + return true; +} +#endif -- 2.31.1
