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=-11.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SIGNED_OFF_BY,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 C8FE7C388F9 for ; Mon, 9 Nov 2020 03:22:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5D1C1206C1 for ; Mon, 9 Nov 2020 03:22:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SYbWhSCy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729176AbgKIDWM (ORCPT ); Sun, 8 Nov 2020 22:22:12 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:43339 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728038AbgKIDWL (ORCPT ); Sun, 8 Nov 2020 22:22:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604892129; 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=gLsBf8rhpmFiThx374/5UmTWgvpMMnV6Dle3sLMtF2g=; b=SYbWhSCyjKJFyWb79HUPSB1Y6qnoEHbjEAhmPZYT2JMVvaMjW3hpY+eCQI2nTlG8hz0INz vJccnSk7qMfwuuA6WpZddT8JsQ1oJ8xcfiXCM9FbOkZ6FHNqaCpF6P0bvLndaq9tNrj0gl X+y6gS/N0uyojJfR7XhvcXGnBStsb6g= 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-392-rqBX1HTMOlW3zJ1ZLC4wGA-1; Sun, 08 Nov 2020 22:22:05 -0500 X-MC-Unique: rqBX1HTMOlW3zJ1ZLC4wGA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E99DD10866A1; Mon, 9 Nov 2020 03:22:03 +0000 (UTC) Received: from [10.72.12.244] (ovpn-12-244.pek2.redhat.com [10.72.12.244]) by smtp.corp.redhat.com (Postfix) with ESMTP id E7A7F6198D; Mon, 9 Nov 2020 03:21:57 +0000 (UTC) Subject: Re: [PATCH v2] vhost-vdpa: fix page pinning leakage in error path (rework) To: si-wei liu , mst@redhat.com, lingshan.zhu@intel.com Cc: joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org References: <1604532796-12757-1-git-send-email-si-wei.liu@oracle.com> <5FA48342.4060404@oracle.com> From: Jason Wang Message-ID: <64fb6179-c5ff-9552-381f-85b63e704057@redhat.com> Date: Mon, 9 Nov 2020 11:21:56 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <5FA48342.4060404@oracle.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/6 上午6:57, si-wei liu wrote: > > On 11/4/2020 7:26 PM, Jason Wang wrote: >> >> On 2020/11/5 上午7:33, Si-Wei Liu wrote: >>> Pinned pages are not properly accounted particularly when >>> mapping error occurs on IOTLB update. Clean up dangling >>> pinned pages for the error path. >>> >>> The memory usage for bookkeeping pinned pages is reverted >>> to what it was before: only one single free page is needed. >>> This helps reduce the host memory demand for VM with a large >>> amount of memory, or in the situation where host is running >>> short of free memory. >>> >>> Fixes: 4c8cf31885f6 ("vhost: introduce vDPA-based backend") >>> Signed-off-by: Si-Wei Liu >>> --- >>> Changes in v2: >>> - Drop the reversion patch >>> - Fix unhandled page leak towards the end of page_list >>> >>>   drivers/vhost/vdpa.c | 79 >>> ++++++++++++++++++++++++++++++++++++++++------------ >>>   1 file changed, 61 insertions(+), 18 deletions(-) >>> >>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c >>> index b6d9016..e112854 100644 >>> --- a/drivers/vhost/vdpa.c >>> +++ b/drivers/vhost/vdpa.c >>> @@ -560,6 +560,8 @@ static int vhost_vdpa_map(struct vhost_vdpa *v, >>>         if (r) >>>           vhost_iotlb_del_range(dev->iotlb, iova, iova + size - 1); >>> +    else >>> +        atomic64_add(size >> PAGE_SHIFT, &dev->mm->pinned_vm); >>>         return r; >>>   } >>> @@ -591,14 +593,16 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>>       unsigned long list_size = PAGE_SIZE / sizeof(struct page *); >>>       unsigned int gup_flags = FOLL_LONGTERM; >>>       unsigned long npages, cur_base, map_pfn, last_pfn = 0; >>> -    unsigned long locked, lock_limit, pinned, i; >>> +    unsigned long lock_limit, sz2pin, nchunks, i; >>>       u64 iova = msg->iova; >>> +    long pinned; >>>       int ret = 0; >>>         if (vhost_iotlb_itree_first(iotlb, msg->iova, >>>                       msg->iova + msg->size - 1)) >>>           return -EEXIST; >>>   +    /* Limit the use of memory for bookkeeping */ >>>       page_list = (struct page **) __get_free_page(GFP_KERNEL); >>>       if (!page_list) >>>           return -ENOMEM; >>> @@ -607,52 +611,75 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>>           gup_flags |= FOLL_WRITE; >>>         npages = PAGE_ALIGN(msg->size + (iova & ~PAGE_MASK)) >> >>> PAGE_SHIFT; >>> -    if (!npages) >>> -        return -EINVAL; >>> +    if (!npages) { >>> +        ret = -EINVAL; >>> +        goto free; >>> +    } >>>         mmap_read_lock(dev->mm); >>>   -    locked = atomic64_add_return(npages, &dev->mm->pinned_vm); >>>       lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT; >>> - >>> -    if (locked > lock_limit) { >>> +    if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) { >>>           ret = -ENOMEM; >>> -        goto out; >>> +        goto unlock; >>>       } >>>         cur_base = msg->uaddr & PAGE_MASK; >>>       iova &= PAGE_MASK; >>> +    nchunks = 0; >>>         while (npages) { >>> -        pinned = min_t(unsigned long, npages, list_size); >>> -        ret = pin_user_pages(cur_base, pinned, >>> -                     gup_flags, page_list, NULL); >>> -        if (ret != pinned) >>> +        sz2pin = min_t(unsigned long, npages, list_size); >>> +        pinned = pin_user_pages(cur_base, sz2pin, >>> +                    gup_flags, page_list, NULL); >>> +        if (sz2pin != pinned) { >>> +            if (pinned < 0) { >>> +                ret = pinned; >>> +            } else { >>> +                unpin_user_pages(page_list, pinned); >>> +                ret = -ENOMEM; >>> +            } >>>               goto out; >>> +        } >>> +        nchunks++; >>>             if (!last_pfn) >>>               map_pfn = page_to_pfn(page_list[0]); >>>   -        for (i = 0; i < ret; i++) { >>> +        for (i = 0; i < pinned; i++) { >>>               unsigned long this_pfn = page_to_pfn(page_list[i]); >>>               u64 csize; >>>                 if (last_pfn && (this_pfn != last_pfn + 1)) { >>>                   /* Pin a contiguous chunk of memory */ >>>                   csize = (last_pfn - map_pfn + 1) << PAGE_SHIFT; >>> -                if (vhost_vdpa_map(v, iova, csize, >>> -                           map_pfn << PAGE_SHIFT, >>> -                           msg->perm)) >>> +                ret = vhost_vdpa_map(v, iova, csize, >>> +                             map_pfn << PAGE_SHIFT, >>> +                             msg->perm); >>> +                if (ret) { >>> +                    /* >>> +                     * Unpin the pages that are left unmapped >>> +                     * from this point on in the current >>> +                     * page_list. The remaining outstanding >>> +                     * ones which may stride across several >>> +                     * chunks will be covered in the common >>> +                     * error path subsequently. >>> +                     */ >>> +                    unpin_user_pages(&page_list[i], >>> +                             pinned - i); >> >> >> Can we simply do last_pfn = this_pfn here? > Nope. They are not contiguous segments of memory. Noted the > conditional (this_pfn != last_pfn + 1) being held here. Right. > >> >> >>>                       goto out; >>> +                } >>> + >>>                   map_pfn = this_pfn; >>>                   iova += csize; >>> +                nchunks = 0; >>>               } >>>                 last_pfn = this_pfn; >>>           } >>>   -        cur_base += ret << PAGE_SHIFT; >>> -        npages -= ret; >>> +        cur_base += pinned << PAGE_SHIFT; >>> +        npages -= pinned; >>>       } >>>         /* Pin the rest chunk */ >>> @@ -660,10 +687,26 @@ static int >>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>>                    map_pfn << PAGE_SHIFT, msg->perm); >>>   out: >>>       if (ret) { >>> +        if (nchunks && last_pfn) { >> >> >> Any reason for checking last_pfn here? >> >> Note that we did: >> >> +        nchunks++; >> >>          if (!last_pfn) >>              map_pfn = page_to_pfn(page_list[0]); > It's for explicit coding to make sure this common error path can be > reused no matter if last_pfn has a sane value assigned or not. I can > change it to an implicit WARN_ON() if need be. Just to make sure I understand. A question, when will we get nchunks != 0 but last_pfn == 0? Thanks > Thanks, > -Siwei > >> >> >> Thanks >> >> >>> +            unsigned long pfn; >>> + >>> +            /* >>> +             * Unpin the outstanding pages which are yet to be >>> +             * mapped but haven't due to vdpa_map() or >>> +             * pin_user_pages() failure. >>> +             * >>> +             * Mapped pages are accounted in vdpa_map(), hence >>> +             * the corresponding unpinning will be handled by >>> +             * vdpa_unmap(). >>> +             */ >>> +            for (pfn = map_pfn; pfn <= last_pfn; pfn++) >>> +                unpin_user_page(pfn_to_page(pfn)); >>> +        } >>>           vhost_vdpa_unmap(v, msg->iova, msg->size); >>> -        atomic64_sub(npages, &dev->mm->pinned_vm); >>>       } >>> +unlock: >>>       mmap_read_unlock(dev->mm); >>> +free: >>>       free_page((unsigned long)page_list); >>>       return ret; >>>   } >> >