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 F37E2C4361B for ; Thu, 17 Dec 2020 18:58:34 +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 5749723118 for ; Thu, 17 Dec 2020 18:58:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5749723118 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]:37976 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpyTx-0004Fy-3P for qemu-devel@archiver.kernel.org; Thu, 17 Dec 2020 13:58:33 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34866) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpyRs-0001sY-RE for qemu-devel@nongnu.org; Thu, 17 Dec 2020 13:56:24 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:24820) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kpyRq-0003Cl-AP for qemu-devel@nongnu.org; Thu, 17 Dec 2020 13:56:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608231380; 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=8csouhW2K+pLOHnfCU3GUNBw2Ja+wB9Cyu3lVtzIqZ4=; b=iVKvJEEEHbKjTpgnVGzQDKjauQOFjz7S4+VjTkEcgF76gnar37tb5A9NsHQlSG6jxHeSi9 4FhwE1HuK7qPrAS8gRJPmoDs4m9r56YLoJs56EcuZ5Xv49RaPxZRsyXESzAWoARfMP7IFh GMdT6LGxqai1MgW87IKUPV0tgPhk1ds= 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-ndtLrJgxPL-EcnQnDho6kw-1; Thu, 17 Dec 2020 13:56:18 -0500 X-MC-Unique: ndtLrJgxPL-EcnQnDho6kw-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 D5F62192202C; Thu, 17 Dec 2020 18:56:16 +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 429725D9E3; Thu, 17 Dec 2020 18:55:56 +0000 (UTC) Subject: Re: [PATCH v3 05/10] vfio: Support for RamDiscardMgr in the !vIOMMU case To: Alex Williamson References: <20201216141200.118742-1-david@redhat.com> <20201216141200.118742-6-david@redhat.com> <20201217113612.0410b143@omen.home> From: David Hildenbrand Organization: Red Hat GmbH Message-ID: Date: Thu, 17 Dec 2020 19:55:55 +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: <20201217113612.0410b143@omen.home> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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 19:36, Alex Williamson wrote: > On Wed, 16 Dec 2020 15:11:55 +0100 > David Hildenbrand wrote: > >> Implement support for RamDiscardMgr, to prepare for virtio-mem >> support. Instead of mapping the whole memory section, we only map >> "populated" parts and update the mapping when notified about >> discarding/population of memory via the RamDiscardListener. Similarly, when >> syncing the dirty bitmaps, sync only the actually mapped (populated) parts >> by replaying via the notifier. >> >> Small mapping granularity is problematic for vfio, because we might run out >> of mappings. Indicate virito-mem as one of the problematic parts when >> warning in vfio_container_dma_reserve() to at least make users aware that >> there is such a limitation. >> >> Using virtio-mem with vfio is still blocked via >> ram_block_discard_disable()/ram_block_discard_require() after this patch. >> >> 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 | 213 +++++++++++++++++++++++++++++++++- >> include/hw/vfio/vfio-common.h | 13 +++ >> 2 files changed, 225 insertions(+), 1 deletion(-) >> >> diff --git a/hw/vfio/common.c b/hw/vfio/common.c >> index 5ad88d476f..b1582be1e8 100644 >> --- a/hw/vfio/common.c >> +++ b/hw/vfio/common.c >> @@ -296,7 +296,8 @@ static void vfio_container_dma_reserve(VFIOContainer *container, >> 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. " >> + warn_report("%s: possibly running out of DMA mappings. E.g., try" >> + " increasing the 'block-size' of virtio-mem devies." >> " Maximum number of DMA mappings: %d", __func__, >> container->dma_max); >> } >> @@ -674,6 +675,146 @@ out: >> rcu_read_unlock(); >> } >> >> +static void vfio_ram_discard_notify_discard(RamDiscardListener *rdl, >> + const MemoryRegion *mr, >> + ram_addr_t offset, ram_addr_t size) >> +{ >> + VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener, >> + listener); >> + const hwaddr mr_start = MAX(offset, vrdl->offset_within_region); >> + const hwaddr mr_end = MIN(offset + size, >> + vrdl->offset_within_region + vrdl->size); >> + const hwaddr iova = mr_start - vrdl->offset_within_region + >> + vrdl->offset_within_address_space; >> + int ret; >> + >> + if (mr_start >= mr_end) { >> + return; >> + } >> + >> + /* Unmap with a single call. */ >> + ret = vfio_dma_unmap(vrdl->container, iova, mr_end - mr_start, NULL); >> + if (ret) { >> + error_report("%s: vfio_dma_unmap() failed: %s", __func__, >> + strerror(-ret)); >> + } >> +} >> + >> +static int vfio_ram_discard_notify_populate(RamDiscardListener *rdl, >> + const MemoryRegion *mr, >> + ram_addr_t offset, ram_addr_t size) >> +{ >> + VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener, >> + listener); >> + const hwaddr mr_end = MIN(offset + size, >> + vrdl->offset_within_region + vrdl->size); >> + hwaddr mr_start = MAX(offset, vrdl->offset_within_region); >> + hwaddr mr_next, iova; >> + void *vaddr; >> + int ret; >> + >> + /* >> + * Map in (aligned within memory region) minimum granularity, so we can >> + * unmap in minimum granularity later. >> + */ >> + for (; mr_start < mr_end; mr_start = mr_next) { >> + mr_next = QEMU_ALIGN_UP(mr_start + 1, vrdl->granularity); >> + mr_next = MIN(mr_next, mr_end); >> + >> + iova = mr_start - vrdl->offset_within_region + >> + vrdl->offset_within_address_space; >> + vaddr = memory_region_get_ram_ptr(vrdl->mr) + mr_start; >> + >> + ret = vfio_dma_map(vrdl->container, iova, mr_next - mr_start, >> + vaddr, mr->readonly); >> + if (ret) { >> + /* Rollback */ >> + vfio_ram_discard_notify_discard(rdl, mr, offset, size); >> + return ret; >> + } >> + } >> + return 0; >> +} >> + >> +static void vfio_ram_discard_notify_discard_all(RamDiscardListener *rdl, >> + const MemoryRegion *mr) >> +{ >> + VFIORamDiscardListener *vrdl = container_of(rdl, VFIORamDiscardListener, >> + listener); >> + int ret; >> + >> + /* Unmap with a single call. */ >> + ret = vfio_dma_unmap(vrdl->container, vrdl->offset_within_address_space, >> + vrdl->size, NULL); >> + if (ret) { >> + error_report("%s: vfio_dma_unmap() failed: %s", __func__, >> + strerror(-ret)); >> + } >> +} >> + >> +static void vfio_register_ram_discard_notifier(VFIOContainer *container, >> + MemoryRegionSection *section) >> +{ >> + RamDiscardMgr *rdm = memory_region_get_ram_discard_mgr(section->mr); >> + RamDiscardMgrClass *rdmc = RAM_DISCARD_MGR_GET_CLASS(rdm); >> + VFIORamDiscardListener *vrdl; >> + >> + vrdl = g_new0(VFIORamDiscardListener, 1); >> + vrdl->container = container; >> + vrdl->mr = section->mr; >> + vrdl->offset_within_region = section->offset_within_region; >> + vrdl->offset_within_address_space = section->offset_within_address_space; >> + vrdl->size = int128_get64(section->size); >> + vrdl->granularity = rdmc->get_min_granularity(rdm, section->mr); >> + vrdl->dma_max = vrdl->size / vrdl->granularity; >> + if (!QEMU_IS_ALIGNED(vrdl->size, vrdl->granularity) || >> + !QEMU_IS_ALIGNED(vrdl->offset_within_region, vrdl->granularity)) { >> + vrdl->dma_max++; >> + } >> + >> + /* Ignore some corner cases not relevant in practice. */ >> + g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_region, TARGET_PAGE_SIZE)); >> + g_assert(QEMU_IS_ALIGNED(vrdl->offset_within_address_space, >> + TARGET_PAGE_SIZE)); >> + g_assert(QEMU_IS_ALIGNED(vrdl->size, TARGET_PAGE_SIZE)); >> + >> + /* We could consume quite some mappings later. */ >> + vfio_container_dma_reserve(container, vrdl->dma_max); > > > Aha, I guess this is where the "reservation" aspect begins to appear. > Should this be its own counter though, perhaps > dma_discard_max_mappings? The populate and discard callbacks could > further divide this into used and outstanding counters. However, TBH > I'm not sure I understand the counters since this is probably the most > robust mapping path where we can actually safely nak a populate I'd like to be able to warn early on fundamental setup issues, not only when accidentally running into these limits later. > callback. Maybe rather than any of these runtime counters we should > just walk the vrdl_list, calculate max mappings, and if that exceeds > some large fraction of available mappings, issue a warning (not that > they wouldn't be useful for tracing). Thanks, Sure, we can calculate max mappings from the vrdl_list. But which fraction to chose? The reservation approach simply considers any mappings (well, except IOMMU because they are kind of special) Guidance on the fraction / #mappings to assume we can use appreciated. Thanks! > > Alex -- Thanks, David / dhildenb