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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 65DE5C4321E for ; Mon, 5 Dec 2022 04:13:03 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1p22q9-00072e-Rh; Sun, 04 Dec 2022 23:12:25 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p22q7-00072U-2h for qemu-devel@nongnu.org; Sun, 04 Dec 2022 23:12:23 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1p22q3-0000Dj-M8 for qemu-devel@nongnu.org; Sun, 04 Dec 2022 23:12:22 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1670213538; 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: in-reply-to:in-reply-to:references:references; bh=FquIk0gpRbAfM46HQrZ3c+t3y1a3l70Vy5WZGsBcvyc=; b=Vq3rDvH6gO/muldmbS3ROTGcfhl6bJSmmKfs6tassge1WyF2dbGbnuTaNs2b994T0NM98A HpHQlrbZd4C9iRCLxDzyokwK6p3f2eljKRl0VKOFqYhv9Nye3XZoXSyxfF6B/G/yYy1HEM Oiup0EGuBhje/TgTA3YqkDcI/+8XqbE= Received: from mail-oo1-f72.google.com (mail-oo1-f72.google.com [209.85.161.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-288-8xzlvctwNLetx_1WKBI-8Q-1; Sun, 04 Dec 2022 23:12:17 -0500 X-MC-Unique: 8xzlvctwNLetx_1WKBI-8Q-1 Received: by mail-oo1-f72.google.com with SMTP id h4-20020a4a6b44000000b004a0a74f306aso1922933oof.2 for ; Sun, 04 Dec 2022 20:12:16 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=FquIk0gpRbAfM46HQrZ3c+t3y1a3l70Vy5WZGsBcvyc=; b=NsRp6rY+vrGHCEkuslegR7rGLOQaga3sjk9W9IHiJte8bVZSkcCL+M6NfnQt+4r12K X+ybzMkThFekPRCjsCPpglTKWVm45O8WLCF1+zKryPTzqDehf7UKL16AR0HymDZ8U78J qTAO9OAmcICL67UT3LYxJeVyMhgfyidvrY7S+ezOlyj/IGHK+IZj87p+EnK4M5eQf2pz I4GBkYu41PjP3AJP1VxAKOlkYAuwkh0bkNmFU8B8nyyg5B7TNAYDjccjcLMyn2X6O7OG HfKUR3UQ8/AfuQlQqMYfl1FxP3+zf3l0h/y4DC0X9Ash2FcPIp0oeKcavPBb0vKac9nT UWaQ== X-Gm-Message-State: ANoB5pnZaFfG3DigGI0hJIUjPkYh78b7QEsYCqCiXoky5QpKjO3dLQ7u q7ZEFSH9DPjSxhfRG5bXF2rIsJ0qKe5KJC+k3LiVIUn8AE0ZOZPp99ioTq72N6Go8Idx8F32vgh 9TWsAbNVVDmkwjMf/Dp4xIUzL26FVFik= X-Received: by 2002:a05:6870:55a9:b0:144:a97b:1ae2 with SMTP id n41-20020a05687055a900b00144a97b1ae2mr613223oao.35.1670213536245; Sun, 04 Dec 2022 20:12:16 -0800 (PST) X-Google-Smtp-Source: AA0mqf50tsPvf2M4q56VH8FH5dJNrFO72JLr9lfPk/znM2mO1sOejEeLmnxnIueevPpCQFHnYXLMNMEPGPm7J4ZpJfc= X-Received: by 2002:a05:6870:55a9:b0:144:a97b:1ae2 with SMTP id n41-20020a05687055a900b00144a97b1ae2mr613207oao.35.1670213535890; Sun, 04 Dec 2022 20:12:15 -0800 (PST) MIME-Version: 1.0 References: <20221129081037.12099-1-jasowang@redhat.com> <20221129081037.12099-4-jasowang@redhat.com> In-Reply-To: From: Jason Wang Date: Mon, 5 Dec 2022 12:12:04 +0800 Message-ID: Subject: Re: [PATCH 3/3] intel-iommu: build iova tree during IOMMU translation To: Peter Xu Cc: mst@redhat.com, qemu-devel@nongnu.org, eric.auger@redhat.com, viktor@daynix.com Content-Type: text/plain; charset="UTF-8" Received-SPF: pass client-ip=170.10.133.124; envelope-from=jasowang@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, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-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: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org ` On Thu, Dec 1, 2022 at 10:59 PM Peter Xu wrote: > > On Thu, Dec 01, 2022 at 04:35:48PM +0800, Jason Wang wrote: > > On Wed, Nov 30, 2022 at 11:17 PM Peter Xu wrote: > > > > > > On Wed, Nov 30, 2022 at 02:33:51PM +0800, Jason Wang wrote: > > > > On Tue, Nov 29, 2022 at 11:57 PM Peter Xu wrote: > > > > > > > > > > On Tue, Nov 29, 2022 at 04:10:37PM +0800, Jason Wang wrote: > > > > > > The IOVA tree is only built during page walk this breaks the device > > > > > > that tries to use UNMAP notifier only. One example is vhost-net, it > > > > > > tries to use UNMAP notifier when vIOMMU doesn't support DEVIOTLB_UNMAP > > > > > > notifier (e.g when dt mode is not enabled). The interesting part is > > > > > > that it doesn't use MAP since it can query the IOMMU translation by > > > > > > itself upon a IOTLB miss. > > > > > > > > > > > > This doesn't work since Qemu doesn't build IOVA tree in IOMMU > > > > > > translation which means the UNMAP notifier won't be triggered during > > > > > > the page walk since Qemu think it is never mapped. This could be > > > > > > noticed when vIOMMU is used with vhost_net but dt is disabled. > > > > > > > > > > > > Fixing this by build the iova tree during IOMMU translation, this > > > > > > makes sure the UNMAP notifier event could be identified during page > > > > > > walk. And we need to walk page table not only for UNMAP notifier but > > > > > > for MAP notifier during PSI. > > > > > > > > > > > > Signed-off-by: Jason Wang > > > > > > --- > > > > > > hw/i386/intel_iommu.c | 43 ++++++++++++++++++------------------------- > > > > > > 1 file changed, 18 insertions(+), 25 deletions(-) > > > > > > > > > > > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c > > > > > > index d025ef2873..edeb62f4b2 100644 > > > > > > --- a/hw/i386/intel_iommu.c > > > > > > +++ b/hw/i386/intel_iommu.c > > > > > > @@ -1834,6 +1834,8 @@ static bool vtd_do_iommu_translate(VTDAddressSpace *vtd_as, PCIBus *bus, > > > > > > uint8_t access_flags; > > > > > > bool rid2pasid = (pasid == PCI_NO_PASID) && s->root_scalable; > > > > > > VTDIOTLBEntry *iotlb_entry; > > > > > > + const DMAMap *mapped; > > > > > > + DMAMap target; > > > > > > > > > > > > /* > > > > > > * We have standalone memory region for interrupt addresses, we > > > > > > @@ -1954,6 +1956,21 @@ out: > > > > > > entry->translated_addr = vtd_get_slpte_addr(slpte, s->aw_bits) & page_mask; > > > > > > entry->addr_mask = ~page_mask; > > > > > > entry->perm = access_flags; > > > > > > + > > > > > > + target.iova = entry->iova; > > > > > > + target.size = entry->addr_mask; > > > > > > + target.translated_addr = entry->translated_addr; > > > > > > + target.perm = entry->perm; > > > > > > + > > > > > > + mapped = iova_tree_find(vtd_as->iova_tree, &target); > > > > > > + if (!mapped) { > > > > > > + /* To make UNMAP notifier work, we need build iova tree here > > > > > > + * in order to have the UNMAP iommu notifier to be triggered > > > > > > + * during the page walk. > > > > > > + */ > > > > > > + iova_tree_insert(vtd_as->iova_tree, &target); > > > > > > + } > > > > > > + > > > > > > return true; > > > > > > > > > > > > error: > > > > > > @@ -2161,31 +2178,7 @@ static void vtd_iotlb_page_invalidate_notify(IntelIOMMUState *s, > > > > > > ret = vtd_dev_to_context_entry(s, pci_bus_num(vtd_as->bus), > > > > > > vtd_as->devfn, &ce); > > > > > > if (!ret && domain_id == vtd_get_domain_id(s, &ce, vtd_as->pasid)) { > > > > > > - if (vtd_as_has_map_notifier(vtd_as)) { > > > > > > - /* > > > > > > - * As long as we have MAP notifications registered in > > > > > > - * any of our IOMMU notifiers, we need to sync the > > > > > > - * shadow page table. > > > > > > - */ > > > > > > - vtd_sync_shadow_page_table_range(vtd_as, &ce, addr, size); > > > > > > - } else { > > > > > > - /* > > > > > > - * For UNMAP-only notifiers, we don't need to walk the > > > > > > - * page tables. We just deliver the PSI down to > > > > > > - * invalidate caches. > > > > > > - */ > > > > > > - IOMMUTLBEvent event = { > > > > > > - .type = IOMMU_NOTIFIER_UNMAP, > > > > > > - .entry = { > > > > > > - .target_as = &address_space_memory, > > > > > > - .iova = addr, > > > > > > - .translated_addr = 0, > > > > > > - .addr_mask = size - 1, > > > > > > - .perm = IOMMU_NONE, > > > > > > - }, > > > > > > - }; > > > > > > - memory_region_notify_iommu(&vtd_as->iommu, 0, event); > > [1] > > > > > > > > > > > Isn't this path the one that will be responsible for pass-through the UNMAP > > > > > events from guest to vhost when there's no MAP notifier requested? > > > > > > > > Yes, but it doesn't do the iova tree removing. More below. > > > > > > > > > > > > > > At least that's what I expected when introducing the iova tree, because for > > > > > unmap-only device hierachy I thought we didn't need the tree at all. > > > > > > > > Then the problem is the UNMAP notifier won't be trigger at all during > > > > DSI page walk in vtd_page_walk_one() because there's no DMAMap stored > > > > in the iova tree.: > > > > > > > > if (!mapped) { > > > > /* Skip since we didn't map this range at all */ > > > > trace_vtd_page_walk_one_skip_unmap(entry->iova, entry->addr_mask); > > > > return 0; > > > > } > > > > > > > > So I choose to build the iova tree in translate then we won't go > > > > within the above condition. > > > > > > That's also why it's weird because IIUC we should never walk a page table > > > at all if there's no MAP notifier regiestered. > > > > If this is true, we probably need to document this somewhere. > > Agree. I'll post a patch. > > > > > > > > > When I'm looking at the walk callers I found that indeed there's one path > > > missing where can cause it to actually walk the pgtables without !MAP, then > > > I also noticed commit f7701e2c7983b6, and I'm wondering what we really want > > > is something like this: > > > > > > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c > > > index a08ee85edf..c46f3db992 100644 > > > --- a/hw/i386/intel_iommu.c > > > +++ b/hw/i386/intel_iommu.c > > > @@ -1536,7 +1536,7 @@ static int vtd_sync_shadow_page_table(VTDAddressSpace *vtd_as) > > > VTDContextEntry ce; > > > IOMMUNotifier *n; > > > > > > - if (!(vtd_as->iommu.iommu_notify_flags & IOMMU_NOTIFIER_IOTLB_EVENTS)) { > > > + if (!vtd_as_has_map_notifier(vtd_as)) { > > > return 0; > > > } > > > > > > So I'm not sure whether this patch is the problem resolver; so far I feel > > > like it's patch 2 who does the real fix. Then we can have the above > > > oneliner so we stop any walks when there's no map notifiers. > > > > > > Thanks, > > > > I may miss something but as state above, the problem is a missing > > UNMAP notification during DSI when there's only UNMAP notifier. > > I got confused too on why we didn't notify UNMAP for DSI already, that's so > weird because I thought it should be there or it should be broken for a > long time.. as we discussed multiple times around this one: > > /* > * Fallback to domain selective flush if no PSI support or > * the size is too big. > */ > if (!cap_pgsel_inv(iommu->cap) || > mask > cap_max_amask_val(iommu->cap)) > iommu->flush.flush_iotlb(iommu, did, 0, 0, > DMA_TLB_DSI_FLUSH); > else > iommu->flush.flush_iotlb(iommu, did, addr | ih, mask, > DMA_TLB_PSI_FLUSH); > > I guess we were just always lucky?.. Probably, or the reason is that we a notifier with UNMAP only is not commonly used before until patch 2. > > > > > To solve it we might have two ways: > > > > 1) build the iova tree during iommu translation then we can correctly > > trigger UNMAP during page walk caused by DSI > > 2) don't do the iova tree walk for !MAP notifier, need new logic to > > trigger UNMAP notifier in PSI/DSI > > > > This patch choose to go 1) (which seems easier at least for -stable). > > Do you mean you prefer to go with 2)? > > Yes. > > IOVA tree is unnecessary overhead IMHO because UNMAP (both IOTLB or > DEVIOTLB unmap) shouldn't need that complexity at all. Using the iova tree > can be accurate on which page got unmapped when the kernel driver used DSI > for a large PSI as shown above, however IMHO it needs more justification > that the pgtable walk is worth the effort. Not to mention if a device in > QEMU that wants to use the iova tree for some reason, one can just register > with MAP and ignore all MAP events, while by default we keep UNMAP simple. > > So we could do: > > (1) Rename vtd_sync_shadow_page_table() to vtd_sync_domain() > (2) instead of optimizing dev-iotlb only there: > > if (!(vtd_as->iommu.iommu_notify_flags & IOMMU_NOTIFIER_IOTLB_EVENTS)) { > return 0; > } > > we should firstly check if UNMAP or DEVUNMAP registered, we directly > send a notification to the whole domain. We need to choose the event > that the register happens with but not both. > > This also reminded me that whether we should sanity check on iommu > notifiers on some invalid cases. E.g. it seems to me when registered with > DEVIOTLB_UNMAP it should not register with either MAP or UNMAP anymore or > it doesn't make sense. It seems it doesn't' harm to allow both UNMAP and DEVIOTLB_UNMAP work. > > One step further, I'm wondering whether the DEV_IOTLB event should exist at > all. Maybe we want to have DEV_IOTLB typed iommu notifier only, This seems cleaner ( I remember we had some discussion before ). > but then > when we got dev-iotlb PSI/DSI we notify with type=UNMAP just like normal > UNMAP events, then in above (2) we can send UNMAP constantly as long as > !MAP. But even if so that'll just be another optional change on top. I'm fine to go without iova-tree. Would you mind to post patches for fix? I can test and include it in this series then. Thanks > > Thanks, > > -- > Peter Xu >