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=-8.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 60EBDC11D3D for ; Thu, 27 Feb 2020 17:43:12 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 3109C24692 for ; Thu, 27 Feb 2020 17:43:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="RnvyHP2T" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3109C24692 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:35600 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j7NBn-00074k-Ew for qemu-devel@archiver.kernel.org; Thu, 27 Feb 2020 12:43:11 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:53536) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j7NB7-0006d3-30 for qemu-devel@nongnu.org; Thu, 27 Feb 2020 12:42:30 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j7NB5-0003Gc-3m for qemu-devel@nongnu.org; Thu, 27 Feb 2020 12:42:28 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:28402 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1j7NB4-0003ER-UY for qemu-devel@nongnu.org; Thu, 27 Feb 2020 12:42:27 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1582825345; h=from:from: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=+8XGG15wbDHKRRjs3PRZ1HsT3EsK19FTrlNsbzA/h0w=; b=RnvyHP2T1ZNUW24on/hwbNvj/smaTJzbnUmpSxXTSWqwBV70c4JKG9AbzL//IGb/Uw/3UG YPsepUR70DAZTiGgjP/hBbHcodigrN1/PZ8bBq8WuMr94oOnGie6TbVoUQDSTiKjcsJ7Db 5u+s5TOCb6640hQfD+evxxSsXRptrh4= 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-176-ORe3IU0JOSaLdamymf0MfA-1; Thu, 27 Feb 2020 12:42:20 -0500 X-MC-Unique: ORe3IU0JOSaLdamymf0MfA-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8F72118C35AA for ; Thu, 27 Feb 2020 17:42:19 +0000 (UTC) Received: from [10.36.116.59] (ovpn-116-59.ams2.redhat.com [10.36.116.59]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 79D9D101D48A; Thu, 27 Feb 2020 17:42:11 +0000 (UTC) Subject: Re: [PATCH v1.1 4/5] KVM: Kick resamplefd for split kernel irqchip To: Peter Xu , qemu-devel@nongnu.org References: <20200227170048.236599-1-peterx@redhat.com> From: Auger Eric Message-ID: <5e69c385-b27c-61d4-5856-21bcf5e9c8f5@redhat.com> Date: Thu, 27 Feb 2020 18:42:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20200227170048.236599-1-peterx@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Paolo Bonzini , Alex Williamson , Cornelia Huck Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Peter, On 2/27/20 6:00 PM, Peter Xu wrote: > This is majorly only for X86 because that's the only one that supports > split irqchip for now. > > When the irqchip is split, we face a dilemma that KVM irqfd will be > enabled, however the slow irqchip is still running in the userspace. > It means that the resamplefd in the kernel irqfds won't take any > effect and it can miss to ack INTx interrupts on EOIs. Won't it always fail to ack INTx? With the above sentence I understand it can work sometimes? > > One example is split irqchip with VFIO INTx, which will break if we > use the VFIO INTx fast path. > > This patch can potentially supports the VFIO fast path again for INTx, > that the IRQ delivery will still use the fast path, while we don't > need to trap MMIOs in QEMU for the device to emulate the EIOs (see the > callers of vfio_eoi() hook). However the EOI of the INTx will still > need to be done from the userspace by caching all the resamplefds in > QEMU and kick properly for IOAPIC EOI broadcast. If I understand correctly this is a one way fast path? Fast path is on the trigger side only: VFIO -> KVM but not on the deactivation side, trapped by the userspace IOAPIC where you directly notify the UNMASK eventfd from userspace. Is that correct? > > When the userspace is responsible for the resamplefd kickup, don't > register it on the kvm_irqfd anymore, because on newer kernels (after > commit 654f1f13ea56, 5.2+) the KVM_IRQFD will fail if with both split > irqchip and resamplefd. This will make sure that the fast path will > work for all supported kernels. > > https://patchwork.kernel.org/patch/10738541/#22609933 > > Suggested-by: Paolo Bonzini > Signed-off-by: Peter Xu > --- > v1.1 changelog: > - when resamplefd is going to be kicked from userspace, don't register > it again in KVM_IRQFD. Tested against upstream kernel. > > accel/kvm/kvm-all.c | 74 ++++++++++++++++++++++++++++++++++++++++-- > accel/kvm/trace-events | 1 + > hw/intc/ioapic.c | 11 +++++-- > include/sysemu/kvm.h | 4 +++ > 4 files changed, 86 insertions(+), 4 deletions(-) > > diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c > index d49b74512a..b766b6e93c 100644 > --- a/accel/kvm/kvm-all.c > +++ b/accel/kvm/kvm-all.c > @@ -159,9 +159,62 @@ static const KVMCapabilityInfo kvm_required_capabilites[] = { > static NotifierList kvm_irqchip_change_notifiers = > NOTIFIER_LIST_INITIALIZER(kvm_irqchip_change_notifiers); > > +struct KVMResampleFd { > + int gsi; > + EventNotifier *resample_event; > + QLIST_ENTRY(KVMResampleFd) node; > +}; > +typedef struct KVMResampleFd KVMResampleFd; > + > +/* > + * Only used with split irqchip where we need to do the resample fd > + * kick for the kernel from userspace. > + */ > +static QLIST_HEAD(, KVMResampleFd) kvm_resample_fd_list = > + QLIST_HEAD_INITIALIZER(kvm_resample_fd_list); > + > #define kvm_slots_lock(kml) qemu_mutex_lock(&(kml)->slots_lock) > #define kvm_slots_unlock(kml) qemu_mutex_unlock(&(kml)->slots_lock) > > +static inline void kvm_resample_fd_remove(int gsi) > +{ > + KVMResampleFd *rfd; > + > + QLIST_FOREACH(rfd, &kvm_resample_fd_list, node) { > + if (rfd->gsi == gsi) { > + QLIST_REMOVE(rfd, node); > + break; > + } > + } > +} > + > +static inline void kvm_resample_fd_insert(int gsi, EventNotifier *event) > +{ > + KVMResampleFd *rfd = g_new0(KVMResampleFd, 1); > + > + rfd->gsi = gsi; > + rfd->resample_event = event; > + > + QLIST_INSERT_HEAD(&kvm_resample_fd_list, rfd, node); > +} > + > +void kvm_resample_fd_notify(int gsi) > +{ > + KVMResampleFd *rfd; > + > + if (!kvm_irqchip_is_split()) { > + return; > + } > + > + QLIST_FOREACH(rfd, &kvm_resample_fd_list, node) { > + if (rfd->gsi == gsi) { > + event_notifier_set(rfd->resample_event); > + trace_kvm_resample_fd_notify(gsi); > + break; > + } > + } > +} > + > int kvm_get_max_memslots(void) > { > KVMState *s = KVM_STATE(current_accel()); > @@ -1642,8 +1695,25 @@ static int kvm_irqchip_assign_irqfd(KVMState *s, EventNotifier *event, > }; > > if (rfd != -1) { > - irqfd.flags |= KVM_IRQFD_FLAG_RESAMPLE; > - irqfd.resamplefd = rfd; > + assert(assign); > + if (kvm_irqchip_is_split()) { > + /* > + * When the slow irqchip (e.g. IOAPIC) is in the > + * userspace, resamplefd will not work because the EOI of > + * the interrupt will be delivered to userspace instead, s/delivered to userspace/handled in userspace > + * the KVM resample fd kick is skipped. The userspace > + * needs to remember the resamplefd and kick it when we > + * receive EOI of this IRQ. Practically we now talk about a VFIO ACTION_UNMASK classical eventfd As such isn't it a bit weird to handle those normal UNMASK eventfds in the KVM code? > + */ > + kvm_resample_fd_insert(virq, resample); > + } else { > + irqfd.flags |= KVM_IRQFD_FLAG_RESAMPLE; > + irqfd.resamplefd = rfd; > + } > + } else if (!assign) { > + if (kvm_irqchip_is_split()) { > + kvm_resample_fd_remove(virq); > + } > } > > if (!kvm_irqfds_enabled()) { > diff --git a/accel/kvm/trace-events b/accel/kvm/trace-events > index 4fb6e59d19..a68eb66534 100644 > --- a/accel/kvm/trace-events > +++ b/accel/kvm/trace-events > @@ -16,4 +16,5 @@ kvm_set_ioeventfd_mmio(int fd, uint64_t addr, uint32_t val, bool assign, uint32_ > kvm_set_ioeventfd_pio(int fd, uint16_t addr, uint32_t val, bool assign, uint32_t size, bool datamatch) "fd: %d @0x%x val=0x%x assign: %d size: %d match: %d" > kvm_set_user_memory(uint32_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, int ret) "Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " ret=%d" > kvm_clear_dirty_log(uint32_t slot, uint64_t start, uint32_t size) "slot#%"PRId32" start 0x%"PRIx64" size 0x%"PRIx32 > +kvm_resample_fd_notify(int gsi) "gsi %d" > > diff --git a/hw/intc/ioapic.c b/hw/intc/ioapic.c > index 15747fe2c2..8c75465c62 100644 > --- a/hw/intc/ioapic.c > +++ b/hw/intc/ioapic.c > @@ -236,8 +236,15 @@ void ioapic_eoi_broadcast(int vector) > for (n = 0; n < IOAPIC_NUM_PINS; n++) { > entry = s->ioredtbl[n]; > > - if ((entry & IOAPIC_VECTOR_MASK) != vector || > - ((entry >> IOAPIC_LVT_TRIGGER_MODE_SHIFT) & 1) != IOAPIC_TRIGGER_LEVEL) { > + if ((entry & IOAPIC_VECTOR_MASK) != vector) { > + continue; > + } > + > + /* Kick resamplefd if KVM is bypassed */ > + kvm_resample_fd_notify(n); KVM is bypassed on the deactivation path but still we call kvm_resample_fd_notify(). > + > + if (((entry >> IOAPIC_LVT_TRIGGER_MODE_SHIFT) & 1) != > + IOAPIC_TRIGGER_LEVEL) { > continue; > } > > diff --git a/include/sysemu/kvm.h b/include/sysemu/kvm.h > index 141342de98..b67552c047 100644 > --- a/include/sysemu/kvm.h > +++ b/include/sysemu/kvm.h > @@ -555,4 +555,8 @@ int kvm_set_one_reg(CPUState *cs, uint64_t id, void *source); > int kvm_get_one_reg(CPUState *cs, uint64_t id, void *target); > struct ppc_radix_page_info *kvm_get_radix_page_info(void); > int kvm_get_max_memslots(void); > + > +/* Notify resamplefd for EOI of specific level triggered interrupts */ > +void kvm_resample_fd_notify(int gsi); > + > #endif > Thanks Eric