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Fri, 20 Mar 2026 06:15:56 -0700 (PDT) From: =?UTF-8?q?Alex=20Benn=C3=A9e?= To: qemu-devel@nongnu.org Cc: Alexander Graf , Peter Maydell , qemu-arm@nongnu.org, Pedro Barbuda , Mohamed Mediouni , =?UTF-8?q?Alex=20Benn=C3=A9e?= Subject: [RFC PATCH 32/35] target/arm: implement WFET Date: Fri, 20 Mar 2026 13:06:03 +0000 Message-ID: <20260320130607.2071996-33-alex.bennee@linaro.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260320130607.2071996-1-alex.bennee@linaro.org> References: <20260320130607.2071996-1-alex.bennee@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=2a00:1450:4864:20::529; envelope-from=alex.bennee@linaro.org; helo=mail-ed1-x529.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, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @linaro.org) X-ZM-MESSAGEID: 1774012591449154100 Now we have the event stream and SEV/SEVL implemented we can finally enable WFET for Aarch64. Signed-off-by: Alex Benn=C3=A9e --- target/arm/tcg/helper-defs.h | 1 + target/arm/tcg/op_helper.c | 80 ++++++++++++++++++++++++++++++++++ target/arm/tcg/translate-a64.c | 15 ++++--- 3 files changed, 89 insertions(+), 7 deletions(-) diff --git a/target/arm/tcg/helper-defs.h b/target/arm/tcg/helper-defs.h index a05f2258f29..31ffcbc6448 100644 --- a/target/arm/tcg/helper-defs.h +++ b/target/arm/tcg/helper-defs.h @@ -56,6 +56,7 @@ DEF_HELPER_1(setend, void, env) DEF_HELPER_2(wfi, void, env, i32) DEF_HELPER_1(wfe, void, env) DEF_HELPER_2(wfit, void, env, i32) +DEF_HELPER_2(wfet, void, env, i32) DEF_HELPER_1(yield, void, env) DEF_HELPER_1(pre_hvc, void, env) DEF_HELPER_2(pre_smc, void, env, i32) diff --git a/target/arm/tcg/op_helper.c b/target/arm/tcg/op_helper.c index fbe160ab70a..8b917b344c9 100644 --- a/target/arm/tcg/op_helper.c +++ b/target/arm/tcg/op_helper.c @@ -521,6 +521,86 @@ void HELPER(wfe)(CPUARMState *env) #endif } =20 +void HELPER(wfet)(CPUARMState *env, uint32_t rd) +{ +#ifdef CONFIG_USER_ONLY + /* + * As for WFIT make it NOP here, because trying to raise EXCP_HLT + * would trigger an abort. + */ + return; +#else + ARMCPU *cpu =3D env_archcpu(env); + CPUState *cs =3D env_cpu(env); + uint32_t excp; + int target_el =3D check_wfx_trap(env, false, &excp); + /* The WFET should time out when CNTVCT_EL0 >=3D the specified value. = */ + uint64_t cntval =3D gt_get_countervalue(env); + uint64_t timeout =3D env->xregs[rd]; + /* + * We want the value that we would get if we read CNTVCT_EL0 from + * the current exception level, so the direct_access offset, not + * the indirect_access one. Compare the pseudocode LocalTimeoutEvent(), + * which calls VirtualCounterTimer(). + */ + uint64_t offset =3D gt_direct_access_timer_offset(env, GTIMER_VIRT); + uint64_t cntvct =3D cntval - offset; + uint64_t nexttick; + int64_t next_event; + + /* + * As for WFE if the event register is already set we can consume + * the event and return immediately. + */ + if (env->event_register.as_bool) { + env->event_register.as_bool =3D false; + return; + } + + + if (cpu_has_work(cs) || cntvct >=3D timeout) { + /* + * Don't bother to go into our "low power state" if + * we would just wake up immediately. + */ + return; + } + + /* We might sleep, so now we check to see if we should trap */ + if (target_el) { + env->pc -=3D 4; + raise_exception(env, excp, syn_wfx(1, 0xe, rd, 1, 2, false), targe= t_el); + } + + /* + * Finally work out if the timeout or event stream will kick in + * earlier. + */ + if (uadd64_overflow(timeout, offset, &nexttick)) { + nexttick =3D UINT64_MAX; + } + if (nexttick > INT64_MAX / gt_cntfrq_period_ns(cpu)) { + nexttick =3D INT64_MAX; + } + + next_event =3D gt_calc_next_event_stream(env); + if (next_event > 0 && next_event < nexttick) { + cpu->waiting_for_event =3D true; + timer_mod(cpu->wfxt_timer, next_event); + } else { + if (nexttick =3D=3D INT64_MAX) { + timer_mod_ns(cpu->wfxt_timer, INT64_MAX); + } else { + timer_mod(cpu->wfxt_timer, nexttick); + } + } + + cs->exception_index =3D EXCP_HLT; + cs->halted =3D 1; + cpu_loop_exit(cs); +#endif +} + void HELPER(yield)(CPUARMState *env) { CPUState *cs =3D env_cpu(env); diff --git a/target/arm/tcg/translate-a64.c b/target/arm/tcg/translate-a64.c index 38a51eb3600..f7d33ac2310 100644 --- a/target/arm/tcg/translate-a64.c +++ b/target/arm/tcg/translate-a64.c @@ -2110,14 +2110,15 @@ static bool trans_WFET(DisasContext *s, arg_WFET *a) return false; } =20 - /* - * We rely here on our WFE implementation being a NOP, so we - * don't need to do anything different to handle the WFET timeout - * from what trans_WFE does. - */ - if (!(tb_cflags(s->base.tb) & CF_PARALLEL)) { - s->base.is_jmp =3D DISAS_WFE; + if (s->ss_active) { + /* Act like a NOP under architectural singlestep */ + return true; } + + gen_a64_update_pc(s, 4); + gen_helper_wfet(tcg_env, tcg_constant_i32(a->rd)); + /* Go back to the main loop to check for interrupts */ + s->base.is_jmp =3D DISAS_EXIT; return true; } =20 --=20 2.47.3