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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0C7F2C678D5 for ; Tue, 21 Feb 2023 03:19:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233471AbjBUDRz (ORCPT ); Mon, 20 Feb 2023 22:17:55 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51580 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233428AbjBUDRx (ORCPT ); Mon, 20 Feb 2023 22:17:53 -0500 Received: from loongson.cn (mail.loongson.cn [114.242.206.163]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 1370923138; Mon, 20 Feb 2023 19:17:46 -0800 (PST) Received: from loongson.cn (unknown [10.20.42.120]) by gateway (Coremail) with SMTP id _____8AxJDTYN_RjOwgDAA--.782S3; Tue, 21 Feb 2023 11:17:44 +0800 (CST) Received: from [10.20.42.120] (unknown [10.20.42.120]) by localhost.localdomain (Coremail) with SMTP id AQAAf8Cxg+XWN_Rj6IE3AA--.2108S3; Tue, 21 Feb 2023 11:17:43 +0800 (CST) Subject: Re: [PATCH v2 08/29] LoongArch: KVM: Implement vcpu handle exit interface To: Paolo Bonzini References: <20230220065735.1282809-1-zhaotianrui@loongson.cn> <20230220065735.1282809-9-zhaotianrui@loongson.cn> Cc: Huacai Chen , WANG Xuerui , Greg Kroah-Hartman , loongarch@lists.linux.dev, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Jens Axboe , Mark Brown , Alex Deucher , Oliver Upton , maobibo@loongson.cn From: Tianrui Zhao Message-ID: Date: Tue, 21 Feb 2023 11:17:42 +0800 User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID: AQAAf8Cxg+XWN_Rj6IE3AA--.2108S3 X-CM-SenderInfo: p2kd03xldq233l6o00pqjv00gofq/ X-Coremail-Antispam: 1Uk129KBjvJXoWxKF47tr1DKFWrGFW5Jry7Wrg_yoWxWr18p3 yvkr429w4kGryxJw1xZrs0vr4jvrZ5Kry7CFy8Wa4ayrsrAwn5A34kKrZ09Fykur1vv3WS vF1UKFn8Cw1qya7anT9S1TB71UUUUjDqnTZGkaVYY2UrUUUUj1kv1TuYvTs0mT0YCTnIWj qI5I8CrVACY4xI64kE6c02F40Ex7xfYxn0WfASr-VFAUDa7-sFnT9fnUUIcSsGvfJTRUUU bqkYFVCjjxCrM7AC8VAFwI0_Jr0_Gr1l1xkIjI8I6I8E6xAIw20EY4v20xvaj40_Wr0E3s 1l1IIY67AEw4v_Jrv_JF1l8cAvFVAK0II2c7xJM28CjxkF64kEwVA0rcxSw2x7M28EF7xv wVC0I7IYx2IY67AKxVW8JVW5JwA2z4x0Y4vE2Ix0cI8IcVCY1x0267AKxVW8JVWxJwA2z4 x0Y4vEx4A2jsIE14v26r4UJVWxJr1l84ACjcxK6I8E87Iv6xkF7I0E14v26r4UJVWxJr1l n4kS14v26r126r1DM2AIxVAIcxkEcVAq07x20xvEncxIr21l57IF6xkI12xvs2x26I8E6x ACxx1l5I8CrVACY4xI64kE6c02F40Ex7xfMcIj6xIIjxv20xvE14v26r126r1DMcIj6I8E 87Iv67AKxVW8JVWxJwAm72CE4IkC6x0Yz7v_Jr0_Gr1lF7xvr2IY64vIr41lc7I2V7IY0V AS07AlzVAYIcxG8wCY1x0262kKe7AKxVWUAVWUtwCF04k20xvY0x0EwIxGrwCFx2IqxVCF s4IE7xkEbVWUJVW8JwCFI7km07C267AKxVWUAVWUtwC20s026c02F40E14v26r1j6r18MI 8I3I0E7480Y4vE14v26r106r1rMI8E67AF67kF1VAFwI0_Jw0_GFylIxkGc2Ij64vIr41l IxAIcVC0I7IYx2IY67AKxVWUCVW8JwCI42IY6xIIjxv20xvEc7CjxVAFwI0_Jr0_Gr1lIx AIcVCF04k26cxKx2IYs7xG6r1j6r1xMIIF0xvEx4A2jsIE14v26r4j6F4UMIIF0xvEx4A2 jsIEc7CjxVAFwI0_Gr0_Gr1UYxBIdaVFxhVjvjDU0xZFpf9x07jFApnUUUUU= Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2023年02月21日 02:45, Paolo Bonzini 写道: > On 2/20/23 07:57, Tianrui Zhao wrote: >> + * Return value is in the form (errcode<<2 | RESUME_FLAG_HOST | >> RESUME_FLAG_NV) > > As far as I can see, RESUME_FLAG_NV does not exist anymore and this is > just copied from arch/mips? > > You can keep RESUME_HOST/RESUME_GUEST for the individual functions, > but here please make it just "1" for resume guest, and "<= 0" for > resume host. This is easy enough to check from assembly and removes > the srai by 2. > >> +static int _kvm_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu) >> +{ >> + unsigned long exst = vcpu->arch.host_estat; >> + u32 intr = exst & 0x1fff; /* ignore NMI */ >> + u32 exccode = (exst & CSR_ESTAT_EXC) >> CSR_ESTAT_EXC_SHIFT; >> + u32 __user *opc = (u32 __user *) vcpu->arch.pc; >> + int ret = RESUME_GUEST, cpu; >> + >> + vcpu->mode = OUTSIDE_GUEST_MODE; >> + >> + /* Set a default exit reason */ >> + run->exit_reason = KVM_EXIT_UNKNOWN; >> + run->ready_for_interrupt_injection = 1; >> + >> + /* >> + * Set the appropriate status bits based on host CPU features, >> + * before we hit the scheduler >> + */ > > Stale comment? I will remove this comment. Thanks Tianrui Zhao > >> + local_irq_enable(); > > Please add guest_state_exit_irqoff() here. I will add this function here. Thanks Tianrui Zhao > >> + kvm_debug("%s: exst: %lx, PC: %p, kvm_run: %p, kvm_vcpu: %p\n", >> + __func__, exst, opc, run, vcpu); > > Please add the information to the kvm_exit tracepoint (thus also > removing variables such as "exst" or "opc" from this function) instead > of calling kvm_debug(). Ok, i will fix the kvm exit tracepoint function. Thanks Tianrui Zhao > >> + trace_kvm_exit(vcpu, exccode); >> + if (exccode) { >> + ret = _kvm_handle_fault(vcpu, exccode); >> + } else { >> + WARN(!intr, "suspicious vm exiting"); >> + ++vcpu->stat.int_exits; >> + >> + if (need_resched()) >> + cond_resched(); > > This "if" is not necessary because there is already a cond_resched() > below. Thanks, I will remove this cond_resched function. Thanks Tianrui Zhao > >> + ret = RESUME_GUEST; > > This "ret" is not necessary because "ret" is already initialized to > RESUME_GUEST above, you can either remove it or remove the initializer. Ok, i will remove this "ret" . Thanks Tianrui Zhao > >> + } >> + >> + cond_resched(); >> + local_irq_disable(); > > At this point, ret is either RESUME_GUEST or RESUME_HOST. So, the > "if"s below are either all taken or all not taken, and most of this code: > > kvm_acquire_timer(vcpu); > _kvm_deliver_intr(vcpu); > > if (signal_pending(current)) { > run->exit_reason = KVM_EXIT_INTR; > ret = (-EINTR << 2) | RESUME_HOST; > ++vcpu->stat.signal_exits; > // no need for a tracepoint here > // trace_kvm_exit(vcpu, KVM_TRACE_EXIT_SIGNAL); > } > > trace_kvm_reenter(vcpu); > > /* > * Make sure the read of VCPU requests in vcpu_reenter() > * callback is not reordered ahead of the write to vcpu->mode, > * or we could miss a TLB flush request while the requester sees > * the VCPU as outside of guest mode and not needing an IPI. > */ > smp_store_mb(vcpu->mode, IN_GUEST_MODE); > > cpu = smp_processor_id(); > _kvm_check_requests(vcpu, cpu); > _kvm_check_vmid(vcpu, cpu); > vcpu->arch.host_eentry = csr_read64(LOONGARCH_CSR_EENTRY); > > /* > * If FPU are enabled (i.e. the guest's FPU context > * is live), restore FCSR0. > */ > if (_kvm_guest_has_fpu(&vcpu->arch) && > read_csr_euen() & (CSR_EUEN_FPEN)) { > kvm_restore_fcsr(&vcpu->arch.fpu); > } > > (all except for the "if (signal_pending(current))" and the final "if") > is pretty much duplicated with kvm_arch_vcpu_ioctl_run(); the > remaining code can also be done from kvm_arch_vcpu_ioctl_run(), the > cost is small. Please move it to a separate function, for example: > > int kvm_pre_enter_guest(struct kvm_vcpu *vcpu) > { > if (signal_pending(current)) { > run->exit_reason = KVM_EXIT_INTR; > ++vcpu->stat.signal_exits; > return -EINTR; > } > > kvm_acquire_timer(vcpu); > _kvm_deliver_intr(vcpu); > > ... > > if (_kvm_guest_has_fpu(&vcpu->arch) && > read_csr_euen() & (CSR_EUEN_FPEN)) { > kvm_restore_fcsr(&vcpu->arch.fpu); > } > return 1; > } > > Call it from _kvm_handle_exit(): > > if (ret == RESUME_HOST) > return 0; > > r = kvm_pre_enter_guest(vcpu); > if (r > 0) { > trace_kvm_reenter(vcpu); > guest_state_enter_irqoff(); > } > > return r; > > and from kvm_arch_vcpu_ioctl_run(): > > local_irq_disable(); > guest_timing_enter_irqoff(); > r = kvm_pre_enter_guest(vcpu); > if (r > 0) { > trace_kvm_enter(vcpu); > /* > * This should actually not be a function pointer, but > * just for clarity */ > */ > guest_state_enter_irqoff(); > r = vcpu->arch.vcpu_run(run, vcpu); > /* guest_state_exit_irqoff() already done. */ > trace_kvm_out(vcpu); > } > guest_timing_exit_irqoff(); > local_irq_enable(); > > out: > kvm_sigset_deactivate(vcpu); > > vcpu_put(vcpu); > return r; > > Paolo Thanks, I will reorganize this code and add the kvm_pre_enter_guest function, and apply it in the vcpu_handle_exit and vcpu_run. Thanks Tianrui Zhao > >> + if (ret == RESUME_GUEST) >> + kvm_acquire_timer(vcpu); >> + >> + if (!(ret & RESUME_HOST)) { >> + _kvm_deliver_intr(vcpu); >> + /* Only check for signals if not already exiting to >> userspace */ >> + if (signal_pending(current)) { >> + run->exit_reason = KVM_EXIT_INTR; >> + ret = (-EINTR << 2) | RESUME_HOST; >> + ++vcpu->stat.signal_exits; >> + trace_kvm_exit(vcpu, KVM_TRACE_EXIT_SIGNAL); >> + } >> + } >> + >> + if (ret == RESUME_GUEST) { >> + trace_kvm_reenter(vcpu); >> + >> + /* >> + * Make sure the read of VCPU requests in vcpu_reenter() >> + * callback is not reordered ahead of the write to vcpu->mode, >> + * or we could miss a TLB flush request while the requester >> sees >> + * the VCPU as outside of guest mode and not needing an IPI. >> + */ >> + smp_store_mb(vcpu->mode, IN_GUEST_MODE); >> + >> + cpu = smp_processor_id(); >> + _kvm_check_requests(vcpu, cpu); >> + _kvm_check_vmid(vcpu, cpu); >> + vcpu->arch.host_eentry = csr_read64(LOONGARCH_CSR_EENTRY); >> + >> + /* >> + * If FPU are enabled (i.e. the guest's FPU context >> + * is live), restore FCSR0. >> + */ >> + if (_kvm_guest_has_fpu(&vcpu->arch) && >> + read_csr_euen() & (CSR_EUEN_FPEN)) { >> + kvm_restore_fcsr(&vcpu->arch.fpu); >> + } >> + } >> + >> + return ret; >> +} >> + >> int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu) >> { >> int i;