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 X-Spam-Level: X-Spam-Status: No, score=-8.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A88A3C47247 for ; Tue, 5 May 2020 00:42:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7D54A206B9 for ; Tue, 5 May 2020 00:42:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FNVV24fC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726963AbgEEAmf (ORCPT ); Mon, 4 May 2020 20:42:35 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:45525 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726531AbgEEAme (ORCPT ); Mon, 4 May 2020 20:42:34 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1588639351; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=sSGS49q3WN+9F6RhzT1InoLhEYrc670AilMF8wVnH2Q=; b=FNVV24fCK2UhpMuQMZ22J5IeitI3S7/u6pa/Zraemq5RMsk3Nf0308HopEgci1ifgg+dLt P62uY235r8A0n13HiavHqB1oZdB8QNBS+wXu7iOPIZy0FJjIED7I2PD+dTvhXyEiK4eNtO UbOMe1MxxdKrSPxFYxW5iaqduDhrHqU= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-471-Ay-GMssaMRmBGeJIydfmkg-1; Mon, 04 May 2020 20:42:27 -0400 X-MC-Unique: Ay-GMssaMRmBGeJIydfmkg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E7F621005510; Tue, 5 May 2020 00:42:25 +0000 (UTC) Received: from localhost.localdomain (vpn2-54-132.bne.redhat.com [10.64.54.132]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5DC802C268; Tue, 5 May 2020 00:42:21 +0000 (UTC) Reply-To: Gavin Shan Subject: Re: [PATCH RFC 6/6] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery To: Vitaly Kuznetsov , x86@kernel.org, kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Paolo Bonzini , Andy Lutomirski , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Sean Christopherson , Wanpeng Li , Jim Mattson References: <20200429093634.1514902-1-vkuznets@redhat.com> <20200429093634.1514902-7-vkuznets@redhat.com> From: Gavin Shan Message-ID: Date: Tue, 5 May 2020 10:42:18 +1000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.0 MIME-Version: 1.0 In-Reply-To: <20200429093634.1514902-7-vkuznets@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vitaly, On 4/29/20 7:36 PM, Vitaly Kuznetsov wrote: > KVM now supports using interrupt for type 2 APF event delivery (page ready > notifications). Switch KVM guests to using it when the feature is present. > > Signed-off-by: Vitaly Kuznetsov > --- > arch/x86/entry/entry_32.S | 5 ++++ > arch/x86/entry/entry_64.S | 5 ++++ > arch/x86/include/asm/hardirq.h | 3 +++ > arch/x86/include/asm/irq_vectors.h | 6 ++++- > arch/x86/include/asm/kvm_para.h | 6 +++++ > arch/x86/kernel/irq.c | 9 +++++++ > arch/x86/kernel/kvm.c | 42 ++++++++++++++++++++++++++++++ > 7 files changed, 75 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S > index b67bae7091d7..d574dadcb2a1 100644 > --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -1475,6 +1475,11 @@ BUILD_INTERRUPT3(hv_stimer0_callback_vector, HYPERV_STIMER0_VECTOR, > > #endif /* CONFIG_HYPERV */ > > +#ifdef CONFIG_KVM_GUEST > +BUILD_INTERRUPT3(kvm_async_pf_vector, KVM_ASYNC_PF_VECTOR, > + kvm_async_pf_intr) > +#endif > + > SYM_CODE_START(page_fault) > ASM_CLAC > pushl $do_page_fault > diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S > index 0e9504fabe52..6f127c1a6547 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1190,6 +1190,11 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ > acrn_hv_callback_vector acrn_hv_vector_handler > #endif > > +#ifdef CONFIG_KVM_GUEST > +apicinterrupt3 KVM_ASYNC_PF_VECTOR \ > + kvm_async_pf_vector kvm_async_pf_intr > +#endif > + > idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=IST_INDEX_DB ist_offset=DB_STACK_OFFSET > idtentry int3 do_int3 has_error_code=0 create_gap=1 > idtentry stack_segment do_stack_segment has_error_code=1 > diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h > index 07533795b8d2..be0fbb15ad7f 100644 > --- a/arch/x86/include/asm/hardirq.h > +++ b/arch/x86/include/asm/hardirq.h > @@ -44,6 +44,9 @@ typedef struct { > unsigned int irq_hv_reenlightenment_count; > unsigned int hyperv_stimer0_count; > #endif > +#ifdef CONFIG_KVM_GUEST > + unsigned int kvm_async_pf_pageready_count; > +#endif > } ____cacheline_aligned irq_cpustat_t; > > DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat); > diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h > index 889f8b1b5b7f..8879a9ecd908 100644 > --- a/arch/x86/include/asm/irq_vectors.h > +++ b/arch/x86/include/asm/irq_vectors.h > @@ -104,7 +104,11 @@ > #define HYPERV_STIMER0_VECTOR 0xed > #endif > > -#define LOCAL_TIMER_VECTOR 0xec > +#ifdef CONFIG_KVM_GUEST > +#define KVM_ASYNC_PF_VECTOR 0xec > +#endif > + > +#define LOCAL_TIMER_VECTOR 0xeb > > #define NR_VECTORS 256 > > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index 9b4df6eaa11a..fde4f21607f9 100644 > --- a/arch/x86/include/asm/kvm_para.h > +++ b/arch/x86/include/asm/kvm_para.h > @@ -4,6 +4,7 @@ > > #include > #include > +#include > #include > > extern void kvmclock_init(void); > @@ -93,6 +94,11 @@ void kvm_async_pf_task_wake(u32 token); > u32 kvm_read_and_reset_pf_reason(void); > extern void kvm_disable_steal_time(void); > void do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address); > +extern void kvm_async_pf_vector(void); > +#ifdef CONFIG_TRACING > +#define trace_kvm_async_pf_vector kvm_async_pf_vector > +#endif > +__visible void __irq_entry kvm_async_pf_intr(struct pt_regs *regs); > > #ifdef CONFIG_PARAVIRT_SPINLOCKS > void __init kvm_spinlock_init(void); > diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c > index c7965ff429c5..a4c2f25ad74d 100644 > --- a/arch/x86/kernel/irq.c > +++ b/arch/x86/kernel/irq.c > @@ -159,6 +159,15 @@ int arch_show_interrupts(struct seq_file *p, int prec) > irq_stats(j)->hyperv_stimer0_count); > seq_puts(p, " Hyper-V stimer0 interrupts\n"); > } > +#endif > +#ifdef CONFIG_KVM_GUEST > + if (test_bit(KVM_ASYNC_PF_VECTOR, system_vectors)) { > + seq_printf(p, "%*s: ", prec, "APF"); > + for_each_online_cpu(j) > + seq_printf(p, "%10u ", > + irq_stats(j)->kvm_async_pf_pageready_count); > + seq_puts(p, " KVM async PF page ready interrupts\n"); > + } > #endif > seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count)); > #if defined(CONFIG_X86_IO_APIC) > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index 6efe0410fb72..1c00c7ba01ff 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -259,9 +259,39 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned lon > rcu_irq_exit(); > break; > } > + > + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) > + wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1); > } > NOKPROBE_SYMBOL(do_async_page_fault); > > +__visible void __irq_entry kvm_async_pf_intr(struct pt_regs *regs) > +{ > + u32 token, reason; > + > + entering_ack_irq(); > + > + inc_irq_stat(kvm_async_pf_pageready_count); > + > + if (__this_cpu_read(apf_reason.enabled)) { > + reason = __this_cpu_read(apf_reason.reason); > + if (reason == KVM_PV_REASON_PAGE_READY) { > + token = __this_cpu_read(apf_reason.token); > + /* > + * Make sure we read 'token' before we reset > + * 'reason' or it can get lost. > + */ > + mb(); > + __this_cpu_write(apf_reason.reason, 0); > + kvm_async_pf_task_wake(token); > + } > + } > + > + wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1); > + > + exiting_irq(); > +} In theory, it's possible the interrupt happens in the context of the suspended process. With the call to kvm_async_pf_task_wake(), the suspended process tries to wake up itself, but it seems it's not working because of aacedf26fb760 ("sched/core: Optimize try_to_wake_up() for local wakeups"). It's one of issue I observed when enabling async page fault for arm64, but not sure it's valid to x86. Thanks, Gavin > static void __init paravirt_ops_setup(void) > { > pv_info.name = "KVM"; > @@ -316,10 +346,17 @@ static void kvm_guest_cpu_init(void) > if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT)) > pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT; > > + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) > + pa |= KVM_ASYNC_PF_DELIVERY_AS_INT; > + > wrmsrl(MSR_KVM_ASYNC_PF_EN, pa); > __this_cpu_write(apf_reason.enabled, 1); > printk(KERN_INFO"KVM setup async PF for cpu %d\n", > smp_processor_id()); > + > + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) > + wrmsrl(MSR_KVM_ASYNC_PF2, KVM_ASYNC_PF2_ENABLED | > + KVM_ASYNC_PF_VECTOR); > } > > if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) { > @@ -649,6 +686,11 @@ static void __init kvm_guest_init(void) > if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) > apic_set_eoi_write(kvm_guest_apic_eoi_write); > > + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) { > + pr_info("KVM using interrupt for async PF page-ready\n"); > + alloc_intr_gate(KVM_ASYNC_PF_VECTOR, kvm_async_pf_vector); > + } > + > #ifdef CONFIG_SMP > smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus; > smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; >