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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,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 C2638C43331 for ; Thu, 26 Mar 2020 13:43:22 +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 8D9EB2076A for ; Thu, 26 Mar 2020 13:43:22 +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="jS1hRj6V" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D9EB2076A 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]:51992 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHSn3-0005wY-Mp for qemu-devel@archiver.kernel.org; Thu, 26 Mar 2020 09:43:21 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:57929) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHSli-00052e-Mr for qemu-devel@nongnu.org; Thu, 26 Mar 2020 09:42:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jHSlg-00020d-2o for qemu-devel@nongnu.org; Thu, 26 Mar 2020 09:41:57 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:22980) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jHSlf-00020Q-UI for qemu-devel@nongnu.org; Thu, 26 Mar 2020 09:41:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585230115; 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=F4dMXh2qmZ3lSD/osxt7xqO3/C6o+ohC6ZeJuu9Wvbk=; b=jS1hRj6V5C10FwB2FCFHtslFET3M62BqzQed2y/wCClh/NfJdY0sBBSBPl5o1fmQ1RaGCV LCCiQ11Pl2zxvrXM2BiQ/T4FPG2S6NAp83+lr8VCpcffrYgbDBmqZH25omGOKEVg6b02se CU1Cpx1Hx2NyB29qSRH/lu7TNSIV2Fw= 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-196-8BYwCuNGOSS3eAH50NwcXw-1; Thu, 26 Mar 2020 09:41:53 -0400 X-MC-Unique: 8BYwCuNGOSS3eAH50NwcXw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id CA634100550D for ; Thu, 26 Mar 2020 13:41:52 +0000 (UTC) Received: from work-vm (ovpn-114-228.ams2.redhat.com [10.36.114.228]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 513365C1B0; Thu, 26 Mar 2020 13:41:46 +0000 (UTC) Date: Thu, 26 Mar 2020 13:41:44 +0000 From: "Dr. David Alan Gilbert" To: Peter Xu Subject: Re: [PATCH RFC 8/9] KVM: Add dirty-ring-size property Message-ID: <20200326134144.GC2713@work-vm> References: <20200205141749.378044-1-peterx@redhat.com> <20200205141749.378044-9-peterx@redhat.com> <20200325200031.GG2635@work-vm> <20200325204214.GD404034@xz-x1> MIME-Version: 1.0 In-Reply-To: <20200325204214.GD404034@xz-x1> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 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 , qemu-devel@nongnu.org, "Michael S . Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Peter Xu (peterx@redhat.com) wrote: > On Wed, Mar 25, 2020 at 08:00:31PM +0000, Dr. David Alan Gilbert wrote: > > > @@ -2077,6 +2079,33 @@ static int kvm_init(MachineState *ms) > > > s->memory_listener.listener.coalesced_io_add =3D kvm_coalesce_mm= io_region; > > > s->memory_listener.listener.coalesced_io_del =3D kvm_uncoalesce_= mmio_region; > > > =20 > > > + /* > > > + * Enable KVM dirty ring if supported, otherwise fall back to > > > + * dirty logging mode > > > + */ > > > + if (s->kvm_dirty_ring_size > 0) { > > > + /* Read the max supported pages */ > > > + ret =3D kvm_vm_check_extension(kvm_state, KVM_CAP_DIRTY_LOG_= RING); > > > + if (ret > 0) { > > > + if (s->kvm_dirty_ring_size > ret) { > > > + error_report("KVM dirty ring size %d too big (maximu= m is %d). " > > > + "Please use a smaller value.", > > > + s->kvm_dirty_ring_size, ret); > > > + goto err; > > > + } > > > + > > > + ret =3D kvm_vm_enable_cap(s, KVM_CAP_DIRTY_LOG_RING, 0, > > > + s->kvm_dirty_ring_size); > > > + if (ret) { > > > + error_report("Enabling of KVM dirty ring failed: %d"= , ret); > > > + goto err; > > > + } > > > + > > > + s->kvm_dirty_gfn_count =3D > > > + s->kvm_dirty_ring_size / sizeof(struct kvm_dirty_gfn= ); > >=20 > > What happens if I was to pass dirty-ring-size=3D1 ? > > Then the count would be 0 and things would get upset somewhere? > > Do you need to check for a minimum postive value? >=20 > The above kvm_vm_enable_cap() should fail directly and QEMU will stop. > Yes we should check it, but kernel will do that in all cases, so I > just didn't do that explicitly again in the userspace. We probably should have that check since you can give them a more obvious error message. > I was planning this to be an advanced feature so the user of this > parameter should know the rules to pass values in. Advanced users just make advanced mistakes :-) I did wonder if perhaps this option should be a count of entries rather than a byte size. > Of course we can introduce another global knob to enable/disable this > feature as a whole, then I can offer a default value for the size > parameter. I just didn't bother that in this RFC version, but I can > switch to that if that's preferred. >=20 > [...] >=20 > > > @@ -3065,6 +3123,12 @@ static void kvm_accel_class_init(ObjectClass *= oc, void *data) > > > NULL, NULL, &error_abort); > > > object_class_property_set_description(oc, "kvm-shadow-mem", > > > "KVM shadow MMU size", &error_abort); > > > + > > > + object_class_property_add(oc, "dirty-ring-size", "int", > > > + kvm_get_dirty_ring_size, kvm_set_dirty_ring_size, > > > + NULL, NULL, &error_abort); > >=20 > > I don't think someone passing in a non-number should cause an abort; > > it should exit, but I don't think it should abort/core. >=20 > It won't - &error_abort is for the operation to add the property. It > should never fail. >=20 > User illegal input will look like this (a graceful exit): >=20 > $ ./x86_64-softmmu/qemu-system-x86_64 -accel kvm,dirty-ring-size=3Da > qemu-system-x86_64: -accel kvm,dirty-ring-size=3Da: Parameter 'dirty-ring= -size' expects int64 OK good. > >=20 > > > + object_class_property_set_description(oc, "dirty-ring-size", > > > + "KVM dirty ring size (<=3D0 to disable)", &error_abort); > > > } > > > =20 > > > static const TypeInfo kvm_accel_type =3D { > > > diff --git a/qemu-options.hx b/qemu-options.hx > > > index 224a8e8712..140bd38726 100644 > > > --- a/qemu-options.hx > > > +++ b/qemu-options.hx > > > @@ -119,6 +119,7 @@ DEF("accel", HAS_ARG, QEMU_OPTION_accel, > > > " kernel-irqchip=3Don|off|split controls accelera= ted irqchip support (default=3Don)\n" > > > " kvm-shadow-mem=3Dsize of KVM shadow MMU in byte= s\n" > > > " tb-size=3Dn (TCG translation block cache size)\= n" > > > + " dirty-ring-size=3Dn (KVM dirty ring size in Byt= es)\n" > > > " thread=3Dsingle|multi (enable multi-threaded TC= G)\n", QEMU_ARCH_ALL) > > > STEXI > > > @item -accel @var{name}[,prop=3D@var{value}[,...]] > > > @@ -140,6 +141,8 @@ irqchip completely is not recommended except for = debugging purposes. > > > Defines the size of the KVM shadow MMU. > > > @item tb-size=3D@var{n} > > > Controls the size (in MiB) of the TCG translation block cache. > > > +@item dirty-ring-size=3D@val{n} > > > +Controls the size (in Bytes) of KVM dirty ring (<=3D0 to disable). > >=20 > > I don't see the point in allowing < 0 ; I'd ban it. >=20 > Sure; I can switch to an uint64. Great. Dave > Thanks, >=20 > --=20 > Peter Xu >=20 -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK