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=-6.8 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_RED 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 730A7C282DD for ; Thu, 9 Jan 2020 16:56:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 392332072A for ; Thu, 9 Jan 2020 16:56:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="c7lvibFY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387926AbgAIQ4m (ORCPT ); Thu, 9 Jan 2020 11:56:42 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:36151 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727738AbgAIQ4m (ORCPT ); Thu, 9 Jan 2020 11:56:42 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578588999; 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=XBEU5CS/Vc8kZY19dgB6cMNAjnA7jgdwFT3l/8agYvI=; b=c7lvibFYKJm27OAfBMkayFniFcDgPt9i8aKD/y9OcD36lN/FYeA+UEFa4XCvKUnVQQEui4 xOisYCRiTq4E0tFhV4xp51wVbD0pxhtjQSJwcQvQDHGzesozV4xGo/7zYSzfEfEm008Bqg af3WDTVxPo/PdF5nB9Y5AquFQ62mpI8= 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-409-VcfvMZO9Mu-e5SS-4M_tGw-1; Thu, 09 Jan 2020 11:56:37 -0500 X-MC-Unique: VcfvMZO9Mu-e5SS-4M_tGw-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 3A4DD9CEF8; Thu, 9 Jan 2020 16:56:36 +0000 (UTC) Received: from w520.home (ovpn-116-128.phx2.redhat.com [10.3.116.128]) by smtp.corp.redhat.com (Postfix) with ESMTP id 17E9A5DA66; Thu, 9 Jan 2020 16:56:10 +0000 (UTC) Date: Thu, 9 Jan 2020 09:56:10 -0700 From: Alex Williamson To: "Michael S. Tsirkin" Cc: Peter Xu , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Christophe de Dinechin , Paolo Bonzini , Sean Christopherson , Yan Zhao , Jason Wang , Kevin Kevin , Vitaly Kuznetsov , "Dr . David Alan Gilbert" , Lei Cao Subject: Re: [PATCH v3 12/21] KVM: X86: Implement ring-based dirty memory tracking Message-ID: <20200109095610.167cd9f0@w520.home> In-Reply-To: <20200109110110-mutt-send-email-mst@kernel.org> References: <20200109145729.32898-1-peterx@redhat.com> <20200109145729.32898-13-peterx@redhat.com> <20200109110110-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 9 Jan 2020 11:29:28 -0500 "Michael S. Tsirkin" wrote: > On Thu, Jan 09, 2020 at 09:57:20AM -0500, Peter Xu wrote: > > This patch is heavily based on previous work from Lei Cao > > and Paolo Bonzini . [1] > > > > KVM currently uses large bitmaps to track dirty memory. These bitmaps > > are copied to userspace when userspace queries KVM for its dirty page > > information. The use of bitmaps is mostly sufficient for live > > migration, as large parts of memory are be dirtied from one log-dirty > > pass to another. However, in a checkpointing system, the number of > > dirty pages is small and in fact it is often bounded---the VM is > > paused when it has dirtied a pre-defined number of pages. Traversing a > > large, sparsely populated bitmap to find set bits is time-consuming, > > as is copying the bitmap to user-space. > > > > A similar issue will be there for live migration when the guest memory > > is huge while the page dirty procedure is trivial. In that case for > > each dirty sync we need to pull the whole dirty bitmap to userspace > > and analyse every bit even if it's mostly zeros. > > > > The preferred data structure for above scenarios is a dense list of > > guest frame numbers (GFN). > > No longer, this uses an array of structs. > > > This patch series stores the dirty list in > > kernel memory that can be memory mapped into userspace to allow speedy > > harvesting. > > > > This patch enables dirty ring for X86 only. However it should be > > easily extended to other archs as well. > > > > [1] https://patchwork.kernel.org/patch/10471409/ > > > > Signed-off-by: Lei Cao > > Signed-off-by: Paolo Bonzini > > Signed-off-by: Peter Xu > > --- > > Documentation/virt/kvm/api.txt | 89 ++++++++++++++++++ > > arch/x86/include/asm/kvm_host.h | 3 + > > arch/x86/include/uapi/asm/kvm.h | 1 + > > arch/x86/kvm/Makefile | 3 +- > > arch/x86/kvm/mmu/mmu.c | 6 ++ > > arch/x86/kvm/vmx/vmx.c | 7 ++ > > arch/x86/kvm/x86.c | 9 ++ > > include/linux/kvm_dirty_ring.h | 55 +++++++++++ > > include/linux/kvm_host.h | 26 +++++ > > include/trace/events/kvm.h | 78 +++++++++++++++ > > include/uapi/linux/kvm.h | 33 +++++++ > > virt/kvm/dirty_ring.c | 162 ++++++++++++++++++++++++++++++++ > > virt/kvm/kvm_main.c | 137 ++++++++++++++++++++++++++- > > 13 files changed, 606 insertions(+), 3 deletions(-) > > create mode 100644 include/linux/kvm_dirty_ring.h > > create mode 100644 virt/kvm/dirty_ring.c > > > > diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt > > index ebb37b34dcfc..708c3e0f7eae 100644 > > --- a/Documentation/virt/kvm/api.txt > > +++ b/Documentation/virt/kvm/api.txt > > @@ -231,6 +231,7 @@ Based on their initialization different VMs may have different capabilities. > > It is thus encouraged to use the vm ioctl to query for capabilities (available > > with KVM_CAP_CHECK_EXTENSION_VM on the vm fd) > > > > + > > 4.5 KVM_GET_VCPU_MMAP_SIZE > > > > Capability: basic > > @@ -243,6 +244,18 @@ The KVM_RUN ioctl (cf.) communicates with userspace via a shared > > memory region. This ioctl returns the size of that region. See the > > KVM_RUN documentation for details. > > > > +Besides the size of the KVM_RUN communication region, other areas of > > +the VCPU file descriptor can be mmap-ed, including: > > + > > +- if KVM_CAP_COALESCED_MMIO is available, a page at > > + KVM_COALESCED_MMIO_PAGE_OFFSET * PAGE_SIZE; for historical reasons, > > + this page is included in the result of KVM_GET_VCPU_MMAP_SIZE. > > + KVM_CAP_COALESCED_MMIO is not documented yet. > > + > > +- if KVM_CAP_DIRTY_LOG_RING is available, a number of pages at > > + KVM_DIRTY_LOG_PAGE_OFFSET * PAGE_SIZE. For more information on > > + KVM_CAP_DIRTY_LOG_RING, see section 8.3. > > + > > > > 4.6 KVM_SET_MEMORY_REGION > > > > @@ -5376,6 +5389,7 @@ CPU when the exception is taken. If this virtual SError is taken to EL1 using > > AArch64, this value will be reported in the ISS field of ESR_ELx. > > > > See KVM_CAP_VCPU_EVENTS for more details. > > + > > 8.20 KVM_CAP_HYPERV_SEND_IPI > > > > Architectures: x86 > > @@ -5383,6 +5397,7 @@ Architectures: x86 > > This capability indicates that KVM supports paravirtualized Hyper-V IPI send > > hypercalls: > > HvCallSendSyntheticClusterIpi, HvCallSendSyntheticClusterIpiEx. > > + > > 8.21 KVM_CAP_HYPERV_DIRECT_TLBFLUSH > > > > Architecture: x86 > > @@ -5396,3 +5411,77 @@ handling by KVM (as some KVM hypercall may be mistakenly treated as TLB > > flush hypercalls by Hyper-V) so userspace should disable KVM identification > > in CPUID and only exposes Hyper-V identification. In this case, guest > > thinks it's running on Hyper-V and only use Hyper-V hypercalls. > > + > > +8.22 KVM_CAP_DIRTY_LOG_RING > > + > > +Architectures: x86 > > +Parameters: args[0] - size of the dirty log ring > > + > > +KVM is capable of tracking dirty memory using ring buffers that are > > +mmaped into userspace; there is one dirty ring per vcpu. > > + > > +One dirty ring is defined as below internally: > > + > > +struct kvm_dirty_ring { > > + u32 dirty_index; > > + u32 reset_index; > > + u32 size; > > + u32 soft_limit; > > + struct kvm_dirty_gfn *dirty_gfns; > > + struct kvm_dirty_ring_indices *indices; > > + int index; > > +}; > > + > > +Dirty GFNs (Guest Frame Numbers) are stored in the dirty_gfns array. > > +For each of the dirty entry it's defined as: > > + > > +struct kvm_dirty_gfn { > > + __u32 pad; > > How about sticking a length here? > This way huge pages can be dirtied in one go. Not just huge pages, but any contiguous range of dirty pages could be reported far more concisely. Thanks, Alex