{"id":2226475,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2226475/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260422125250.1303100-33-alex.bennee@linaro.org/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/1.1/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20260422125250.1303100-33-alex.bennee@linaro.org>","date":"2026-04-22T12:52:49","name":"[v3,32/32] target/arm: implement WFET","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"a7b0b0d61484822f01a2a22add0289d09479ef58","submitter":{"id":39532,"url":"http://patchwork.ozlabs.org/api/1.1/people/39532/?format=json","name":"Alex Bennée","email":"alex.bennee@linaro.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20260422125250.1303100-33-alex.bennee@linaro.org/mbox/","series":[{"id":501008,"url":"http://patchwork.ozlabs.org/api/1.1/series/501008/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=501008","date":"2026-04-22T12:52:20","name":"target/arm: fully model WFxT instructions for A-profile","version":3,"mbox":"http://patchwork.ozlabs.org/series/501008/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2226475/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2226475/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=linaro.org header.i=@linaro.org header.a=rsa-sha256\n header.s=google header.b=L5OvlGbJ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org\n (client-ip=209.51.188.17; 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charset=UTF-8","Content-Transfer-Encoding":"8bit","Received-SPF":"pass client-ip=2a00:1450:4864:20::343;\n envelope-from=alex.bennee@linaro.org; helo=mail-wm1-x343.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,\n DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1,\n RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001,\n SPF_PASS=-0.001 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":"qemu development ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"Now we have the event stream and SEV/SEVL implemented we can finally\nenable WFET for Aarch64.\n\nSigned-off-by: Alex Bennée \n\n---\nv2\n - fix exception syndrome by using enum value\n - use env->halt_reason\nv3\n - fix check_wfx_trap(s/false/true/) as it is a WFE\n---\n target/arm/tcg/helper-defs.h | 1 +\n target/arm/tcg/op_helper.c | 80 ++++++++++++++++++++++++++++++++++\n target/arm/tcg/translate-a64.c | 15 ++++---\n 3 files changed, 89 insertions(+), 7 deletions(-)","diff":"diff --git a/target/arm/tcg/helper-defs.h b/target/arm/tcg/helper-defs.h\nindex ebdf09be38a..5e4d828dd55 100644\n--- a/target/arm/tcg/helper-defs.h\n+++ b/target/arm/tcg/helper-defs.h\n@@ -56,6 +56,7 @@ DEF_HELPER_1(setend, void, env)\n DEF_HELPER_2(wfi, void, env, i32)\n DEF_HELPER_2(wfe, void, env, i32)\n DEF_HELPER_2(wfit, void, env, i32)\n+DEF_HELPER_2(wfet, void, env, i32)\n DEF_HELPER_1(yield, void, env)\n DEF_HELPER_1(pre_hvc, void, env)\n DEF_HELPER_2(pre_smc, void, env, i32)\ndiff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c\nindex fe34c94e890..112e0c2eb1a 100644\n--- a/target/arm/tcg/op_helper.c\n+++ b/target/arm/tcg/op_helper.c\n@@ -620,6 +620,86 @@ void HELPER(wfe)(CPUARMState *env, uint32_t insn_len)\n #endif\n }\n \n+void HELPER(wfet)(CPUARMState *env, uint32_t rd)\n+{\n+#ifdef CONFIG_USER_ONLY\n+ /*\n+ * As for WFIT make it NOP here, because trying to raise EXCP_HLT\n+ * would trigger an abort.\n+ */\n+ return;\n+#else\n+ ARMCPU *cpu = env_archcpu(env);\n+ CPUState *cs = env_cpu(env);\n+ uint32_t excp;\n+ int target_el = check_wfx_trap(env, true, &excp);\n+ /* The WFET should time out when CNTVCT_EL0 >= the specified value. */\n+ uint64_t cntval = gt_get_countervalue(env);\n+ uint64_t timeout = env->xregs[rd];\n+ /*\n+ * We want the value that we would get if we read CNTVCT_EL0 from\n+ * the current exception level, so the direct_access offset, not\n+ * the indirect_access one. Compare the pseudocode LocalTimeoutEvent(),\n+ * which calls VirtualCounterTimer().\n+ */\n+ uint64_t offset = gt_direct_access_timer_offset(env, GTIMER_VIRT);\n+ uint64_t cntvct = cntval - offset;\n+ uint64_t nexttick;\n+ int64_t next_event;\n+\n+ /*\n+ * As for WFE if the event register is already set we can consume\n+ * the event and return immediately.\n+ */\n+ if (env->event_register) {\n+ env->event_register = false;\n+ return;\n+ }\n+\n+\n+ if (cpu_has_work(cs) || cntvct >= timeout) {\n+ /*\n+ * Don't bother to go into our \"low power state\" if\n+ * we would just wake up immediately.\n+ */\n+ return;\n+ }\n+\n+ /* We might sleep, so now we check to see if we should trap */\n+ if (target_el) {\n+ env->pc -= 4;\n+ raise_exception(env, excp, syn_wfx(1, 0xe, rd, true, WFET, false), target_el);\n+ }\n+\n+ /*\n+ * Finally work out if the timeout or event stream will kick in\n+ * earlier.\n+ */\n+ if (uadd64_overflow(timeout, offset, &nexttick)) {\n+ nexttick = UINT64_MAX;\n+ }\n+ if (nexttick > INT64_MAX / gt_cntfrq_period_ns(cpu)) {\n+ nexttick = INT64_MAX;\n+ }\n+\n+ next_event = gt_calc_next_event_stream(env);\n+ if (next_event > 0 && next_event < nexttick) {\n+ timer_mod(cpu->wfxt_timer, next_event);\n+ } else {\n+ if (nexttick == INT64_MAX) {\n+ timer_mod_ns(cpu->wfxt_timer, INT64_MAX);\n+ } else {\n+ timer_mod(cpu->wfxt_timer, nexttick);\n+ }\n+ }\n+\n+ env->halt_reason = HALT_WFE;\n+ cs->exception_index = EXCP_HLT;\n+ cs->halted = 1;\n+ cpu_loop_exit(cs);\n+#endif\n+}\n+\n void HELPER(yield)(CPUARMState *env)\n {\n CPUState *cs = env_cpu(env);\ndiff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c\nindex 83b2a6e848f..c8c8a27956b 100644\n--- a/target/arm/tcg/translate-a64.c\n+++ b/target/arm/tcg/translate-a64.c\n@@ -2093,14 +2093,15 @@ static bool trans_WFET(DisasContext *s, arg_WFET *a)\n return false;\n }\n \n- /*\n- * We rely here on our WFE implementation being a NOP, so we\n- * don't need to do anything different to handle the WFET timeout\n- * from what trans_WFE does.\n- */\n- if (!(tb_cflags(s->base.tb) & CF_PARALLEL)) {\n- s->base.is_jmp = DISAS_WFE;\n+ if (s->ss_active) {\n+ /* Act like a NOP under architectural singlestep */\n+ return true;\n }\n+\n+ gen_a64_update_pc(s, 4);\n+ gen_helper_wfet(tcg_env, tcg_constant_i32(a->rd));\n+ /* Go back to the main loop to check for interrupts */\n+ s->base.is_jmp = DISAS_EXIT;\n return true;\n }\n \n","prefixes":["v3","32/32"]}