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[27.33.251.27]) by smtp.gmail.com with ESMTPSA id w200-20020a627bd1000000b00518e1251197sm14007936pfc.148.2022.07.20.06.34.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Jul 2022 06:34:02 -0700 (PDT) From: Nicholas Piggin To: qemu-ppc@nongnu.org Cc: Nicholas Piggin , qemu-devel@nongnu.org, =?utf-8?q?V?= =?utf-8?q?=C3=ADctor_Colombo?= Subject: [PATCH v3] target/ppc: Implement new wait variants Date: Wed, 20 Jul 2022 23:33:52 +1000 Message-Id: <20220720133352.904263-1-npiggin@gmail.com> X-Mailer: git-send-email 2.35.1 MIME-Version: 1.0 Received-SPF: pass client-ip=2607:f8b0:4864:20::630; envelope-from=npiggin@gmail.com; helo=mail-pl1-x630.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ISA v2.06 adds new variations of wait, specified by the WC field. These are not all compatible with the prior wait implementation, because they add additional conditions that cause the processor to resume, which can cause software to hang or run very slowly. ISA v3.0 changed the wait opcode and removed the new variants (retaining the WC field but making non-zero values reserved). ISA v3.1 added new WC values to the new wait opcode, and added a PL field. This implements the new wait encoding and supports WC variants with no-op implementations, which provides basic correctness as explained in comments. Signed-off-by: Nicholas Piggin Reviewed-by: Víctor Colombo Tested-by: Joel Stanley Reviewed-by: Daniel Henrique Barboza --- v3: - Add EXTRACT_HELPERs - Reserved fields should be ignored, not trap. - v3.1 defines special case of reserved PL values being treated as a no-op when WC=2. - Change code organization to (hopefully) be easier to follow each ISA / variation. - Tested old wait variant with Linux e6500 boot and verify that gen_wait is called and takes the expected path. Thanks, Nick target/ppc/internal.h | 3 ++ target/ppc/translate.c | 96 ++++++++++++++++++++++++++++++++++++++---- 2 files changed, 91 insertions(+), 8 deletions(-) diff --git a/target/ppc/internal.h b/target/ppc/internal.h index 2add128cd1..57c0a42a6b 100644 --- a/target/ppc/internal.h +++ b/target/ppc/internal.h @@ -168,6 +168,9 @@ EXTRACT_HELPER_SPLIT_3(DX, 10, 6, 6, 5, 16, 1, 1, 0, 0) /* darn */ EXTRACT_HELPER(L, 16, 2); #endif +/* wait */ +EXTRACT_HELPER(WC, 21, 2); +EXTRACT_HELPER(PL, 16, 2); /*** Jump target decoding ***/ /* Immediate address */ diff --git a/target/ppc/translate.c b/target/ppc/translate.c index 1d6daa4608..e0a835ac90 100644 --- a/target/ppc/translate.c +++ b/target/ppc/translate.c @@ -4066,12 +4066,91 @@ static void gen_sync(DisasContext *ctx) /* wait */ static void gen_wait(DisasContext *ctx) { - TCGv_i32 t0 = tcg_const_i32(1); - tcg_gen_st_i32(t0, cpu_env, - -offsetof(PowerPCCPU, env) + offsetof(CPUState, halted)); - tcg_temp_free_i32(t0); - /* Stop translation, as the CPU is supposed to sleep from now */ - gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next); + uint32_t wc; + + if (ctx->insns_flags & PPC_WAIT) { + /* v2.03-v2.07 define an older incompatible 'wait' encoding. */ + + if (ctx->insns_flags2 & PPC2_PM_ISA206) { + /* v2.06 introduced the WC field. WC > 0 may be treated as no-op. */ + wc = WC(ctx->opcode); + } else { + wc = 0; + } + + } else if (ctx->insns_flags2 & PPC2_ISA300) { + /* v3.0 defines a new 'wait' encoding. */ + wc = WC(ctx->opcode); + if (ctx->insns_flags2 & PPC2_ISA310) { + uint32_t pl = PL(ctx->opcode); + + /* WC 1,2 may be treated as no-op. WC 3 is reserved. */ + if (wc == 3) { + gen_invalid(ctx); + return; + } + + /* PL 1-3 are reserved. If WC=2 then the insn is treated as noop. */ + if (pl > 0 && wc != 2) { + gen_invalid(ctx); + return; + } + + } else { /* ISA300 */ + /* WC 1-3 are reserved */ + if (wc > 0) { + gen_invalid(ctx); + return; + } + } + + } else { + warn_report("wait instruction decoded with wrong ISA flags."); + gen_invalid(ctx); + return; + } + + /* + * wait without WC field or with WC=0 waits for an exception / interrupt + * to occur. + */ + if (wc == 0) { + TCGv_i32 t0 = tcg_const_i32(1); + tcg_gen_st_i32(t0, cpu_env, + -offsetof(PowerPCCPU, env) + offsetof(CPUState, halted)); + tcg_temp_free_i32(t0); + /* Stop translation, as the CPU is supposed to sleep from now */ + gen_exception_nip(ctx, EXCP_HLT, ctx->base.pc_next); + } + + /* + * Other wait types must not just wait until an exception occurs because + * ignoring their other wake-up conditions could cause a hang. + * + * For v2.06 and 2.07, wc=1,2,3 are architected but may be implemented as + * no-ops. + * + * wc=1 and wc=3 explicitly allow the instruction to be treated as a no-op. + * + * wc=2 waits for an implementation-specific condition, such could be + * always true, so it can be implemented as a no-op. + * + * For v3.1, wc=1,2 are architected but may be implemented as no-ops. + * + * wc=1 (waitrsv) waits for an exception or a reservation to be lost. + * Reservation-loss may have implementation-specific conditions, so it + * can be implemented as a no-op. + * + * wc=2 waits for an exception or an amount of time to pass. This + * amount is implementation-specific so it can be implemented as a + * no-op. + * + * ISA v3.1 allows for execution to resume "in the rare case of + * an implementation-dependent event", so in any case software must + * not depend on the architected resumption condition to become + * true, so no-op implementations should be architecturally correct + * (if suboptimal). + */ } #if defined(TARGET_PPC64) @@ -6852,8 +6931,9 @@ GEN_HANDLER2(stdcx_, "stdcx.", 0x1F, 0x16, 0x06, 0x00000000, PPC_64B), GEN_HANDLER_E(stqcx_, 0x1F, 0x16, 0x05, 0, PPC_NONE, PPC2_LSQ_ISA207), #endif GEN_HANDLER(sync, 0x1F, 0x16, 0x12, 0x039FF801, PPC_MEM_SYNC), -GEN_HANDLER(wait, 0x1F, 0x1E, 0x01, 0x03FFF801, PPC_WAIT), -GEN_HANDLER_E(wait, 0x1F, 0x1E, 0x00, 0x039FF801, PPC_NONE, PPC2_ISA300), +/* ISA v3.0 changed the extended opcode from 62 to 30 */ +GEN_HANDLER(wait, 0x1F, 0x1E, 0x01, 0x039FF801, PPC_WAIT), +GEN_HANDLER_E(wait, 0x1F, 0x1E, 0x00, 0x039CF801, PPC_NONE, PPC2_ISA300), GEN_HANDLER(b, 0x12, 0xFF, 0xFF, 0x00000000, PPC_FLOW), GEN_HANDLER(bc, 0x10, 0xFF, 0xFF, 0x00000000, PPC_FLOW), GEN_HANDLER(bcctr, 0x13, 0x10, 0x10, 0x00000000, PPC_FLOW),