From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 76DE9C433EF for ; Wed, 20 Jul 2022 19:34:53 +0000 (UTC) Received: from localhost ([::1]:46328 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oEFTA-0005Dy-0G for qemu-devel@archiver.kernel.org; Wed, 20 Jul 2022 15:34:52 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33972) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oEFQa-0004I3-Kl for qemu-devel@nongnu.org; Wed, 20 Jul 2022 15:32:14 -0400 Received: from mail-yb1-xb31.google.com ([2607:f8b0:4864:20::b31]:40468) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1oEFQX-0004kv-HS for qemu-devel@nongnu.org; Wed, 20 Jul 2022 15:32:12 -0400 Received: by mail-yb1-xb31.google.com with SMTP id k85so31097691ybk.7 for ; Wed, 20 Jul 2022 12:32:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=atishpatra.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=Qxyf4Jqyy+GteCuP3ZcFzmCsFQ2kDyIngECFia3D5gg=; b=rbM6vFl6R3TVQPACWeP3ghsHZ60PlZ+7D9MMRGOGFB9qoGbOmZY9gON/Ye6kbJRLEd fbLbYSAJb8Vktt0Ehlz4psDeoYI3YHtx3UOOCGEsKRLTnAfnta9YoAeArdffl2ZYCRZJ 2ed+EszsOgCCbtXjxfxXSXAVaAn19xBEUc1bs= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=Qxyf4Jqyy+GteCuP3ZcFzmCsFQ2kDyIngECFia3D5gg=; b=EU1y+JNnV7t9NdvYyE4sCsQEXyMKY9wTg1Txw2wn49OE83R5TbT/w77HeZjedKje4R S/gCS1y81+ieb3wAAEJo6aa7DyRjfH2SpOvOCl/TtjdixdbTU86nomUUmCwhon4gGAi3 NhoXQnHea6J6G7Tr+iz2qG+dmK8dVxdoHOEJQxCcITPbVHiHg2pD7ai1ggoQr5xtwWGZ XYRBhAl0sWotsLB0uPedBMv4byUAenQFkwH9Z2aVX+NN9yydJGnnk4WXMw/A7b5jj/Im PO+2DzQ0MjsR90lK0w2S4WLjY3/RxnzBOVHqw4Y48uEPbz1p8fegTEN1/HqM/ChLs9I8 M6Pg== X-Gm-Message-State: AJIora+l4ulTSrz2wnA76x1QvRRhZw0fhZQrOIEyWA9qBC+7y+8MbUrj OAkZ2SIgXnFErysb95xDSwJ/lJpHbdsjQ7nlcHvY X-Google-Smtp-Source: AGRyM1tXImXvAlloLTZ6+lJKu5rb6dotj64D4uxQcSJIxPwr/LHl2OIbWy/WDYAMrjmNKGn0BgT532TAdVwdCD+L0FY= X-Received: by 2002:a25:ca46:0:b0:670:963f:c533 with SMTP id a67-20020a25ca46000000b00670963fc533mr4860989ybg.473.1658345527708; Wed, 20 Jul 2022 12:32:07 -0700 (PDT) MIME-Version: 1.0 References: <20220531180321.34942-1-atishp@rivosinc.com> <20220531180321.34942-3-atishp@rivosinc.com> In-Reply-To: From: Atish Patra Date: Wed, 20 Jul 2022 12:31:57 -0700 Message-ID: Subject: Re: [PATCH v5 2/3] target/riscv: Add stimecmp support To: Alistair Francis , Alistair Francis Cc: Atish Kumar Patra , "qemu-devel@nongnu.org Developers" , Bin Meng , Palmer Dabbelt , "open list:RISC-V" , Anup Patel , Anup Patel Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=2607:f8b0:4864:20::b31; envelope-from=atishp@atishpatra.org; helo=mail-yb1-xb31.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, 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" On Wed, Jun 15, 2022 at 8:25 PM Anup Patel wrote: > > On Thu, Jun 16, 2022 at 8:08 AM Alistair Francis wrote: > > > > On Thu, Jun 16, 2022 at 4:21 AM Atish Kumar Patra wrote: > > > > > > On Wed, Jun 8, 2022 at 12:19 AM Alistair Francis wrote: > > > > > > > > On Mon, Jun 6, 2022 at 2:23 AM Atish Patra wrote: > > > > > > > > > > On Thu, Jun 2, 2022 at 12:02 AM Alistair Francis wrote: > > > > > > > > > > > > On Wed, Jun 1, 2022 at 4:16 AM Atish Patra wrote: > > > > > > > > > > > > > > stimecmp allows the supervisor mode to update stimecmp CSR directly > > > > > > > to program the next timer interrupt. This CSR is part of the Sstc > > > > > > > extension which was ratified recently. > > > > > > > > > > > > > > Signed-off-by: Atish Patra > > > > > > > --- > > > > > > > target/riscv/cpu.c | 8 ++++ > > > > > > > target/riscv/cpu.h | 5 ++ > > > > > > > target/riscv/cpu_bits.h | 4 ++ > > > > > > > target/riscv/csr.c | 81 +++++++++++++++++++++++++++++++ > > > > > > > target/riscv/machine.c | 1 + > > > > > > > target/riscv/meson.build | 3 +- > > > > > > > target/riscv/time_helper.c | 98 ++++++++++++++++++++++++++++++++++++++ > > > > > > > target/riscv/time_helper.h | 30 ++++++++++++ > > > > > > > 8 files changed, 229 insertions(+), 1 deletion(-) > > > > > > > create mode 100644 target/riscv/time_helper.c > > > > > > > create mode 100644 target/riscv/time_helper.h > > > > > > > > > > > > > > diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c > > > > > > > index 19f4e8294042..d58dd2f857a7 100644 > > > > > > > --- a/target/riscv/cpu.c > > > > > > > +++ b/target/riscv/cpu.c > > > > > > > @@ -23,6 +23,7 @@ > > > > > > > #include "qemu/log.h" > > > > > > > #include "cpu.h" > > > > > > > #include "internals.h" > > > > > > > +#include "time_helper.h" > > > > > > > #include "exec/exec-all.h" > > > > > > > #include "qapi/error.h" > > > > > > > #include "qemu/error-report.h" > > > > > > > @@ -779,7 +780,12 @@ static void riscv_cpu_init(Object *obj) > > > > > > > #ifndef CONFIG_USER_ONLY > > > > > > > qdev_init_gpio_in(DEVICE(cpu), riscv_cpu_set_irq, > > > > > > > IRQ_LOCAL_MAX + IRQ_LOCAL_GUEST_MAX); > > > > > > > + > > > > > > > + if (cpu->cfg.ext_sstc) { > > > > > > > + riscv_timer_init(cpu); > > > > > > > + } > > > > > > > #endif /* CONFIG_USER_ONLY */ > > > > > > > + > > > > > > > } > > > > > > > > > > > > > > static Property riscv_cpu_properties[] = { > > > > > > > @@ -806,6 +812,7 @@ static Property riscv_cpu_properties[] = { > > > > > > > DEFINE_PROP_BOOL("mmu", RISCVCPU, cfg.mmu, true), > > > > > > > DEFINE_PROP_BOOL("pmp", RISCVCPU, cfg.pmp, true), > > > > > > > DEFINE_PROP_BOOL("debug", RISCVCPU, cfg.debug, true), > > > > > > > + DEFINE_PROP_BOOL("sstc", RISCVCPU, cfg.ext_sstc, true), > > > > > > > > > > > > Do we want this enabled by default? > > > > > > > > > > > > > > > > sstc extension will result in performance improvements as it avoids > > > > > the SBI calls & interrupt forwarding > > > > > path. That's why I think it should be enabled by default. > > > > > > > > > > > > > > > > > > > DEFINE_PROP_STRING("priv_spec", RISCVCPU, cfg.priv_spec), > > > > > > > DEFINE_PROP_STRING("vext_spec", RISCVCPU, cfg.vext_spec), > > > > > > > @@ -965,6 +972,7 @@ static void riscv_isa_string_ext(RISCVCPU *cpu, char **isa_str, int max_str_len) > > > > > > > ISA_EDATA_ENTRY(zbs, ext_zbs), > > > > > > > ISA_EDATA_ENTRY(zve32f, ext_zve32f), > > > > > > > ISA_EDATA_ENTRY(zve64f, ext_zve64f), > > > > > > > + ISA_EDATA_ENTRY(sstc, ext_sstc), > > > > > > > ISA_EDATA_ENTRY(svinval, ext_svinval), > > > > > > > ISA_EDATA_ENTRY(svnapot, ext_svnapot), > > > > > > > ISA_EDATA_ENTRY(svpbmt, ext_svpbmt), > > > > > > > diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h > > > > > > > index 1119d5201066..9a5e02f217ba 100644 > > > > > > > --- a/target/riscv/cpu.h > > > > > > > +++ b/target/riscv/cpu.h > > > > > > > @@ -276,6 +276,9 @@ struct CPUArchState { > > > > > > > uint64_t mfromhost; > > > > > > > uint64_t mtohost; > > > > > > > > > > > > > > + /* Sstc CSRs */ > > > > > > > + uint64_t stimecmp; > > > > > > > + > > > > > > > /* physical memory protection */ > > > > > > > pmp_table_t pmp_state; > > > > > > > target_ulong mseccfg; > > > > > > > @@ -329,6 +332,7 @@ struct CPUArchState { > > > > > > > float_status fp_status; > > > > > > > > > > > > > > /* Fields from here on are preserved across CPU reset. */ > > > > > > > + QEMUTimer *stimer; /* Internal timer for S-mode interrupt */ > > > > > > > > > > > > > > hwaddr kernel_addr; > > > > > > > hwaddr fdt_addr; > > > > > > > @@ -379,6 +383,7 @@ struct RISCVCPUConfig { > > > > > > > bool ext_counters; > > > > > > > bool ext_ifencei; > > > > > > > bool ext_icsr; > > > > > > > + bool ext_sstc; > > > > > > > bool ext_svinval; > > > > > > > bool ext_svnapot; > > > > > > > bool ext_svpbmt; > > > > > > > diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h > > > > > > > index 4e5b630f5965..29d0e4a1be01 100644 > > > > > > > --- a/target/riscv/cpu_bits.h > > > > > > > +++ b/target/riscv/cpu_bits.h > > > > > > > @@ -215,6 +215,10 @@ > > > > > > > #define CSR_STVAL 0x143 > > > > > > > #define CSR_SIP 0x144 > > > > > > > > > > > > > > +/* Sstc supervisor CSRs */ > > > > > > > +#define CSR_STIMECMP 0x14D > > > > > > > +#define CSR_STIMECMPH 0x15D > > > > > > > + > > > > > > > /* Supervisor Protection and Translation */ > > > > > > > #define CSR_SPTBR 0x180 > > > > > > > #define CSR_SATP 0x180 > > > > > > > diff --git a/target/riscv/csr.c b/target/riscv/csr.c > > > > > > > index 245f007e66e1..48d07911ae14 100644 > > > > > > > --- a/target/riscv/csr.c > > > > > > > +++ b/target/riscv/csr.c > > > > > > > @@ -21,6 +21,7 @@ > > > > > > > #include "qemu/log.h" > > > > > > > #include "qemu/timer.h" > > > > > > > #include "cpu.h" > > > > > > > +#include "time_helper.h" > > > > > > > #include "qemu/main-loop.h" > > > > > > > #include "exec/exec-all.h" > > > > > > > #include "sysemu/cpu-timers.h" > > > > > > > @@ -537,6 +538,76 @@ static RISCVException read_timeh(CPURISCVState *env, int csrno, > > > > > > > return RISCV_EXCP_NONE; > > > > > > > } > > > > > > > > > > > > > > +static RISCVException sstc(CPURISCVState *env, int csrno) > > > > > > > +{ > > > > > > > + CPUState *cs = env_cpu(env); > > > > > > > + RISCVCPU *cpu = RISCV_CPU(cs); > > > > > > > + > > > > > > > + if (!cpu->cfg.ext_sstc || !env->rdtime_fn) { > > > > > > > + return RISCV_EXCP_ILLEGAL_INST; > > > > > > > + } > > > > > > > + > > > > > > > + if (env->priv == PRV_M) { > > > > > > > + return RISCV_EXCP_NONE; > > > > > > > + } > > > > > > > + > > > > > > > + if (env->priv != PRV_S) { > > > > > > > + return RISCV_EXCP_ILLEGAL_INST; > > > > > > > + } > > > > > > > + > > > > > > > + /* > > > > > > > + * No need of separate function for rv32 as menvcfg stores both menvcfg > > > > > > > + * menvcfgh for RV32. > > > > > > > + */ > > > > > > > + if (!(get_field(env->mcounteren, COUNTEREN_TM) && > > > > > > > + get_field(env->menvcfg, MENVCFG_STCE))) { > > > > > > > + return RISCV_EXCP_ILLEGAL_INST; > > > > > > > + } > > > > > > > + > > > > > > > + return RISCV_EXCP_NONE; > > > > > > > +} > > > > > > > + > > > > > > > +static RISCVException read_stimecmp(CPURISCVState *env, int csrno, > > > > > > > + target_ulong *val) > > > > > > > +{ > > > > > > > + *val = env->stimecmp; > > > > > > > + return RISCV_EXCP_NONE; > > > > > > > +} > > > > > > > + > > > > > > > +static RISCVException read_stimecmph(CPURISCVState *env, int csrno, > > > > > > > + target_ulong *val) > > > > > > > +{ > > > > > > > + *val = env->stimecmp >> 32; > > > > > > > + return RISCV_EXCP_NONE; > > > > > > > +} > > > > > > > + > > > > > > > +static RISCVException write_stimecmp(CPURISCVState *env, int csrno, > > > > > > > + target_ulong val) > > > > > > > +{ > > > > > > > + RISCVCPU *cpu = env_archcpu(env); > > > > > > > + > > > > > > > + if (riscv_cpu_mxl(env) == MXL_RV32) { > > > > > > > + env->stimecmp = deposit64(env->stimecmp, 0, 32, (uint64_t)val); > > > > > > > + } else { > > > > > > > + env->stimecmp = val; > > > > > > > + } > > > > > > > + > > > > > > > + riscv_timer_write_timecmp(cpu, env->stimer, env->stimecmp, 0, MIP_STIP); > > > > > > > + > > > > > > > + return RISCV_EXCP_NONE; > > > > > > > +} > > > > > > > + > > > > > > > +static RISCVException write_stimecmph(CPURISCVState *env, int csrno, > > > > > > > + target_ulong val) > > > > > > > +{ > > > > > > > + RISCVCPU *cpu = env_archcpu(env); > > > > > > > + > > > > > > > + env->stimecmp = deposit64(env->stimecmp, 32, 32, (uint64_t)val); > > > > > > > + riscv_timer_write_timecmp(cpu, env->stimer, env->stimecmp, 0, MIP_STIP); > > > > > > > + > > > > > > > + return RISCV_EXCP_NONE; > > > > > > > +} > > > > > > > + > > > > > > > /* Machine constants */ > > > > > > > > > > > > > > #define M_MODE_INTERRUPTS ((uint64_t)(MIP_MSIP | MIP_MTIP | MIP_MEIP)) > > > > > > > @@ -1515,6 +1586,12 @@ static RISCVException rmw_mip64(CPURISCVState *env, int csrno, > > > > > > > new_val |= env->external_seip * MIP_SEIP; > > > > > > > } > > > > > > > > > > > > > > + if (cpu->cfg.ext_sstc && (env->priv == PRV_M) && > > > > > > > + get_field(env->menvcfg, MENVCFG_STCE)) { > > > > > > > + /* sstc extension forbids STIP & VSTIP to be writeable in mip */ > > > > > > > + mask = mask & ~(MIP_STIP | MIP_VSTIP); > > > > > > > + } > > > > > > > + > > > > > > > if (mask) { > > > > > > > old_mip = riscv_cpu_update_mip(cpu, mask, (new_val & mask)); > > > > > > > } else { > > > > > > > @@ -3341,6 +3418,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = { > > > > > > > [CSR_SCAUSE] = { "scause", smode, read_scause, write_scause }, > > > > > > > [CSR_STVAL] = { "stval", smode, read_stval, write_stval }, > > > > > > > [CSR_SIP] = { "sip", smode, NULL, NULL, rmw_sip }, > > > > > > > + [CSR_STIMECMP] = { "stimecmp", sstc, read_stimecmp, write_stimecmp, > > > > > > > + .min_priv_ver = PRIV_VERSION_1_12_0 }, > > > > > > > + [CSR_STIMECMPH] = { "stimecmph", sstc, read_stimecmph, write_stimecmph, > > > > > > > + .min_priv_ver = PRIV_VERSION_1_12_0 }, > > > > > > > > > > > > > > /* Supervisor Protection and Translation */ > > > > > > > [CSR_SATP] = { "satp", smode, read_satp, write_satp }, > > > > > > > diff --git a/target/riscv/machine.c b/target/riscv/machine.c > > > > > > > index 7d85de0b1d49..ee02bfc18916 100644 > > > > > > > --- a/target/riscv/machine.c > > > > > > > +++ b/target/riscv/machine.c > > > > > > > @@ -334,6 +334,7 @@ const VMStateDescription vmstate_riscv_cpu = { > > > > > > > VMSTATE_UINTTL(env.mscratch, RISCVCPU), > > > > > > > VMSTATE_UINT64(env.mfromhost, RISCVCPU), > > > > > > > VMSTATE_UINT64(env.mtohost, RISCVCPU), > > > > > > > + VMSTATE_UINT64(env.stimecmp, RISCVCPU), > > > > > > > > > > > > > > VMSTATE_END_OF_LIST() > > > > > > > }, > > > > > > > diff --git a/target/riscv/meson.build b/target/riscv/meson.build > > > > > > > index 2c20f3dd8e9c..1243d019148e 100644 > > > > > > > --- a/target/riscv/meson.build > > > > > > > +++ b/target/riscv/meson.build > > > > > > > @@ -29,7 +29,8 @@ riscv_softmmu_ss.add(files( > > > > > > > 'pmp.c', > > > > > > > 'debug.c', > > > > > > > 'monitor.c', > > > > > > > - 'machine.c' > > > > > > > + 'machine.c', > > > > > > > + 'time_helper.c' > > > > > > > )) > > > > > > > > > > > > > > target_arch += {'riscv': riscv_ss} > > > > > > > diff --git a/target/riscv/time_helper.c b/target/riscv/time_helper.c > > > > > > > new file mode 100644 > > > > > > > index 000000000000..f3fb5eac7b7b > > > > > > > --- /dev/null > > > > > > > +++ b/target/riscv/time_helper.c > > > > > > > @@ -0,0 +1,98 @@ > > > > > > > +/* > > > > > > > + * RISC-V timer helper implementation. > > > > > > > + * > > > > > > > + * Copyright (c) 2022 Rivos Inc. > > > > > > > + * > > > > > > > + * This program is free software; you can redistribute it and/or modify it > > > > > > > + * under the terms and conditions of the GNU General Public License, > > > > > > > + * version 2 or later, as published by the Free Software Foundation. > > > > > > > + * > > > > > > > + * This program is distributed in the hope it will be useful, but WITHOUT > > > > > > > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > > > > > > > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > > > > > > > + * more details. > > > > > > > + * > > > > > > > + * You should have received a copy of the GNU General Public License along with > > > > > > > + * this program. If not, see . > > > > > > > + */ > > > > > > > + > > > > > > > +#include "qemu/osdep.h" > > > > > > > +#include "qemu/log.h" > > > > > > > +#include "cpu_bits.h" > > > > > > > +#include "time_helper.h" > > > > > > > +#include "hw/intc/riscv_aclint.h" > > > > > > > + > > > > > > > +static void riscv_stimer_cb(void *opaque) > > > > > > > +{ > > > > > > > + RISCVCPU *cpu = opaque; > > > > > > > + riscv_cpu_update_mip(cpu, MIP_STIP, BOOL_TO_MASK(1)); > > > > > > > +} > > > > > > > + > > > > > > > +/* > > > > > > > + * Called when timecmp is written to update the QEMU timer or immediately > > > > > > > + * trigger timer interrupt if mtimecmp <= current timer value. > > > > > > > + */ > > > > > > > +void riscv_timer_write_timecmp(RISCVCPU *cpu, QEMUTimer *timer, > > > > > > > + uint64_t timecmp, uint64_t delta, > > > > > > > + uint32_t timer_irq) > > > > > > > +{ > > > > > > > + uint64_t diff, ns_diff, next > > > > > > > + CPURISCVState *env = &cpu->env; > > > > > > > + RISCVAclintMTimerState *mtimer = env->rdtime_fn_arg; > > > > > > > + uint32_t timebase_freq = mtimer->timebase_freq; > > > > > > > + uint64_t rtc_r = env->rdtime_fn(env->rdtime_fn_arg) + delta; > > > > > > > > > > > > Can't we just pass mtimer here directly? > > > > > > > > > > > > > > > > Yeah. rank's recent patch changed the argument to mtimer instead of > > > > > timebase_freq. > > > > > I forgot to change here while rebasing. I will change this. > > > > > > > > > > > Ok, so I realise this is based on the aclint, but I've now confused myself. > > > > > > > > > > > > So rtc_r is the current time in ticks > > > > > > > > > > > > > + > > > > > > > + if (timecmp <= rtc_r) { > > > > > > > + /* > > > > > > > + * If we're setting an stimecmp value in the "past", > > > > > > > + * immediately raise the timer interrupt > > > > > > > + */ > > > > > > > + riscv_cpu_update_mip(cpu, timer_irq, BOOL_TO_MASK(1)); > > > > > > > + return; > > > > > > > + } > > > > > > > + > > > > > > > + /* Clear the [V]STIP bit in mip */ > > > > > > > + riscv_cpu_update_mip(cpu, timer_irq, BOOL_TO_MASK(0)); > > > > > > > + > > > > > > > + /* otherwise, set up the future timer interrupt */ > > > > > > > + diff = timecmp - rtc_r; > > > > > > > > > > > > timecmp is the absolute time we want the interrupt in ticks > > > > > > > > > > > > > + /* back to ns (note args switched in muldiv64) */ > > > > > > > + ns_diff = muldiv64(diff, NANOSECONDS_PER_SECOND, timebase_freq); > > > > > > > > > > > > ns_diff is the amount of ns in the future we want the interrupt to occur > > > > > > > > > > > > > + > > > > > > > + /* > > > > > > > + * check if ns_diff overflowed and check if the addition would potentially > > > > > > > + * overflow > > > > > > > + */ > > > > > > > + if ((NANOSECONDS_PER_SECOND > timebase_freq && ns_diff < diff) || > > > > > > > + ns_diff > INT64_MAX) { > > > > > > > + next = INT64_MAX; > > > > > > > + } else { > > > > > > > + /* > > > > > > > + * as it is very unlikely qemu_clock_get_ns will return a value > > > > > > > + * greater than INT64_MAX, no additional check is needed for an > > > > > > > + * unsigned integer overflow. > > > > > > > > > > > > I don't think qemu_clock_get_ns() can return a value larger than INT64_MAX > > > > > > > > > > > > > > > > Yup as the return type is int64_t :) > > > > > > > > > > > > + */ > > > > > > > + next = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + ns_diff; > > > > > > > > > > > > next is the absolute time (in ns) that we want the interrupt to occur. > > > > > > > > > > > > So we end up performing > > > > > > > > > > > > ((timecmp - now_in_ticks) in ns) + now_in_ns > > > > > > > > > > > > Can't we just convert timecmp to ns and then set that directly with timer_mod()? > > > > > > > > > > > > > > > > That should work for all the case except > > > > > if ((NANOSECONDS_PER_SECOND > timebase_freq && ns_diff < diff) > > > > > > > > > > where we cap the next to INT64_MAX. > > > > > > > > Couldn't we catch that with this? > > > > > > > > /* Convert to ns */ > > > > timecmp_ns = muldiv64(timecmp, NANOSECONDS_PER_SECOND, timebase_freq); > > > > > > > > if ((NANOSECONDS_PER_SECOND > timebase_freq && timecmp_ns < timecmp) > > > > > > > > > > Yes. But I think there are other problems. > > > > > > 1. Currently, we are converting the difference between timecmp & rtc_r > > > to nanoseconds. > > > The diff will always be a smaller number that won't overflow for a long time. > > > However, if we convert the timestamp directly to nanoseconds, it may > > > overflow more often. > > > > But then we add it back to now right, so it seems pretty similar. This > > is ok as is, it just seemed to be more complex then required > > > > > > > > 2. For vstimecmp, we have htimedelta which relies on unsigned integer wrapping. > > > If we convert directly convert the vstimecmp to nanoseconds, it will > > > be problematic to factor in the > > > htimedelta. > > > > Ah ok, I haven't looked at that part yet. > > Converting htimedelta to nanoseconds is a bigger problem because it is > added to time CSR value and typically it is a negative number stored as > unsigned long so it's value will be a very high (e.g. 0xFFFFFFxx_yyyyyyyy). > Now, if we convert such a large value (at 10MHz) to nanoseconds (at 1GHz) > then it will overflow and become a small unsigned long value. > > To avoid such integer overflow issues, we should convert timer ticks to > nanoseconds just before programming the QEMU timer. > > Regards, > Anup > @Alistair: Do we need any more improvement here ? If not I can just rebase and resend. > > > > Alistair > > > > > > > > Let me know if I missed something. > > > > > > > > > > > > > Don't we need this condition to check ? If yes, we have to compute > > > > > ns_diff anyways. > > > > > > > > > > > > + /* > > > > > > > + * if ns_diff is INT64_MAX next may still be outside the range > > > > > > > + * of a signed integer. > > > > > > > + */ > > > > > > > + next = MIN(next, INT64_MAX); > > > > > > > > > > > > Also, what happens if the guest sets a timecmp larger than INT64_MAX? > > > > > > We will then end up rounding it down, maybe we should store the > > > > > > timecmp and check it in riscv_stimer_cb? > > > > > > > > > > > > > > > > The 'cpu' is passed as an opaque parameter. Thus, we can retrieve the timecmp in > > > > > riscv_stimer_cb. > > > > > > > > > > At that point, if stimecmp > INT64_MAX, we need to reprogram the > > > > > counter with the overflow amount > > > > > instead of triggering the interrupt. Correct ? > > > > > > > > Yep! Exactly > > > > > > > > > > > > > > It is probably unlikely to hit that condition, we should do what is > > > > > correct. It should be fixed for mtimecmp in aclint driver > > > > > as well. > > > > > > > > Yeah, I agree it's unlikely, but this extension is expected to be used > > > > by higher performance implements, like servers, where it *could* > > > > happen > > > > > > > > Alistair > > > > > > > > > > > > > > > Alistair > > > > > > > > > > > > > + } > > > > > > > + > > > > > > > + timer_mod(timer, next); > > > > > > > +} > > > > > > > + > > > > > > > +void riscv_timer_init(RISCVCPU *cpu) > > > > > > > +{ > > > > > > > + CPURISCVState *env; > > > > > > > + > > > > > > > + if (!cpu) { > > > > > > > + return; > > > > > > > + } > > > > > > > + > > > > > > > + env = &cpu->env; > > > > > > > + env->stimer = timer_new_ns(QEMU_CLOCK_VIRTUAL, &riscv_stimer_cb, cpu); > > > > > > > + env->stimecmp = 0; > > > > > > > + > > > > > > > +} > > > > > > > diff --git a/target/riscv/time_helper.h b/target/riscv/time_helper.h > > > > > > > new file mode 100644 > > > > > > > index 000000000000..7b3cdcc35020 > > > > > > > --- /dev/null > > > > > > > +++ b/target/riscv/time_helper.h > > > > > > > @@ -0,0 +1,30 @@ > > > > > > > +/* > > > > > > > + * RISC-V timer header file. > > > > > > > + * > > > > > > > + * Copyright (c) 2022 Rivos Inc. > > > > > > > + * > > > > > > > + * This program is free software; you can redistribute it and/or modify it > > > > > > > + * under the terms and conditions of the GNU General Public License, > > > > > > > + * version 2 or later, as published by the Free Software Foundation. > > > > > > > + * > > > > > > > + * This program is distributed in the hope it will be useful, but WITHOUT > > > > > > > + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or > > > > > > > + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for > > > > > > > + * more details. > > > > > > > + * > > > > > > > + * You should have received a copy of the GNU General Public License along with > > > > > > > + * this program. If not, see . > > > > > > > + */ > > > > > > > + > > > > > > > +#ifndef RISCV_TIME_HELPER_H > > > > > > > +#define RISCV_TIME_HELPER_H > > > > > > > + > > > > > > > +#include "cpu.h" > > > > > > > +#include "qemu/timer.h" > > > > > > > + > > > > > > > +void riscv_timer_write_timecmp(RISCVCPU *cpu, QEMUTimer *timer, > > > > > > > + uint64_t timecmp, uint64_t delta, > > > > > > > + uint32_t timer_irq); > > > > > > > +void riscv_timer_init(RISCVCPU *cpu); > > > > > > > + > > > > > > > +#endif > > > > > > > -- > > > > > > > 2.25.1 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > Regards, > > > > > Atish > > -- Regards, Atish