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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,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 1AAD1C2BB9A for ; Thu, 17 Dec 2020 19:07:08 +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 7645F239EB for ; Thu, 17 Dec 2020 19:07:07 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7645F239EB 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]:49550 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpycE-0000ta-A0 for qemu-devel@archiver.kernel.org; Thu, 17 Dec 2020 14:07:06 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:36506) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpyaB-0008LJ-0c for qemu-devel@nongnu.org; Thu, 17 Dec 2020 14:04:59 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:35935) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kpya8-0003zu-Ld for qemu-devel@nongnu.org; Thu, 17 Dec 2020 14:04:58 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608231896; 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=sdGmaKMgXEXBGTV/JpEglw+lUZI7JvbNx1J3chl8BzU=; b=R2RCeuR7MA+CL4bEMOVJatSg4wUYyG9oTv5m9RhAYeN8NgcUibLIaqBYdEDKhO/cSA5Ay0 zulLvB+aP3SETjBZwWuA7SNpJ3gatXxZ/A6dis0N1aG0mSDNwbAvDmaSS6xyt4GTmTQZ7r dtcRkGCtp1xue9xSKhfIDYxY64NyFu0= 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-365-owzZjaIxMOy9eVL6d3mrcg-1; Thu, 17 Dec 2020 14:04:49 -0500 X-MC-Unique: owzZjaIxMOy9eVL6d3mrcg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0F97C59; Thu, 17 Dec 2020 19:04:48 +0000 (UTC) Received: from [10.36.113.93] (ovpn-113-93.ams2.redhat.com [10.36.113.93]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3051518993; Thu, 17 Dec 2020 19:04:30 +0000 (UTC) Subject: Re: [PATCH v3 04/10] vfio: Query and store the maximum number of DMA mappings To: Alex Williamson References: <20201216141200.118742-1-david@redhat.com> <20201216141200.118742-5-david@redhat.com> <20201217105512.78a2ef71@omen.home> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 17 Dec 2020 20:04:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: <20201217105512.78a2ef71@omen.home> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: Pankaj Gupta , Wei Yang , "Michael S. Tsirkin" , Jonathan Cameron , qemu-devel@nongnu.org, Peter Xu , "Dr . David Alan Gilbert" , Auger Eric , teawater , Igor Mammedov , Paolo Bonzini , Marek Kedzierski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 17.12.20 18:55, Alex Williamson wrote: > On Wed, 16 Dec 2020 15:11:54 +0100 > David Hildenbrand wrote: > >> Let's query the maximum number of DMA mappings by querying the available >> mappings when creating the container. >> >> In addition, count the number of DMA mappings and warn when we would >> exceed it. This is a preparation for RamDiscardMgr which might >> create quite some DMA mappings over time, and we at least want to warn >> early that the QEMU setup might be problematic. Use "reserved" >> terminology, so we can use this to reserve mappings before they are >> actually created. > > This terminology doesn't make much sense to me, we're not actually > performing any kind of reservation. I see you spotted the second user which actually performs reservations. > >> Note: don't reserve vIOMMU DMA mappings - using the vIOMMU region size >> divided by the mapping page size might be a bad indication of what will >> happen in practice - we might end up warning all the time. > > This suggests we're not really tracking DMA "reservations" at all. > Would something like dma_regions_mappings be a more appropriate > identifier for the thing you're trying to count? We might as well also Right now I want to count - Mappings we know we will definitely have (counted in this patch) - Mappings we know we could eventually have later (RamDiscardMgr) > keep a counter for dma_iommu_mappings where the sum of those two should > stay below dma_max_mappings. We could, however, tracking active IOMMU mappings when removing a memory region from the address space isn't easily possible - we do a single vfio_dma_unmap() which might span multiple mappings. Same applies to RamDiscardMgr. Hard to count how many mappings we actually *currently* have using that approach. > >> Cc: Paolo Bonzini >> Cc: "Michael S. Tsirkin" >> Cc: Alex Williamson >> Cc: Dr. David Alan Gilbert >> Cc: Igor Mammedov >> Cc: Pankaj Gupta >> Cc: Peter Xu >> Cc: Auger Eric >> Cc: Wei Yang >> Cc: teawater >> Cc: Marek Kedzierski >> Signed-off-by: David Hildenbrand >> --- >> hw/vfio/common.c | 34 ++++++++++++++++++++++++++++++++++ >> include/hw/vfio/vfio-common.h | 2 ++ >> 2 files changed, 36 insertions(+) >> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c >> index 6ff1daa763..5ad88d476f 100644 >> --- a/hw/vfio/common.c >> +++ b/hw/vfio/common.c >> @@ -288,6 +288,26 @@ const MemoryRegionOps vfio_region_ops = { >> }, >> }; >> >> +static void vfio_container_dma_reserve(VFIOContainer *container, >> + unsigned long dma_mappings) >> +{ >> + bool warned = container->dma_reserved > container->dma_max; >> + >> + container->dma_reserved += dma_mappings; >> + if (!warned && container->dma_max && >> + container->dma_reserved > container->dma_max) { >> + warn_report("%s: possibly running out of DMA mappings. " >> + " Maximum number of DMA mappings: %d", __func__, >> + container->dma_max); > > If we kept track of all the mappings we could predict better than > "possibly". Tracing support to track a high water mark might be useful > too. It's an early warning for reservations e.g., on fundamental setup issues with virtio-mem. [...] >> diff --git a/include/hw/vfio/vfio-common.h b/include/hw/vfio/vfio-common.h >> index 6141162d7a..fed0e85f66 100644 >> --- a/include/hw/vfio/vfio-common.h >> +++ b/include/hw/vfio/vfio-common.h >> @@ -88,6 +88,8 @@ typedef struct VFIOContainer { >> uint64_t dirty_pgsizes; >> uint64_t max_dirty_bitmap_size; >> unsigned long pgsizes; >> + unsigned int dma_max; >> + unsigned long dma_reserved; > > If dma_max is unsigned int, why do we need an unsigned long to track > how many are in use? Thanks, My thinking was that some vfio IOMMU types don't have such a limit (dma_max == -1) and could allow for more. But thinking again, such a huge number of mappings is highly unrealistic :) -- Thanks, David / dhildenb