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 12609C2D0A3 for ; Wed, 4 Nov 2020 01:58:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 98C112242C for ; Wed, 4 Nov 2020 01:58:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="N+EBIz1Y" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730280AbgKDB63 (ORCPT ); Tue, 3 Nov 2020 20:58:29 -0500 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:26992 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728301AbgKDB63 (ORCPT ); Tue, 3 Nov 2020 20:58:29 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604455106; 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=/UAWX/l1lwuyu7yfRs5oPUEbyXJnB4GGE7rO3NI4ilQ=; b=N+EBIz1YlxvhhMWnPmuhL/nL25nDuidVCcCqcf7nIoatG/gQ1jahSYDsJTp1EaoTq9XS/w ZDqeFkwRi0HyKBiJF5qCagnD0/rpr0rrYzMp7EOrUo33wAz86KgGCdGq3+mgowfcSJ1jMD YmRGFEewcHdiWxavFs0rRhM4V1tO59c= 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-458-UaK9TAl2MnS_77rMomrX-g-1; Tue, 03 Nov 2020 20:58:22 -0500 X-MC-Unique: UaK9TAl2MnS_77rMomrX-g-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 5457A8030C8; Wed, 4 Nov 2020 01:58:21 +0000 (UTC) Received: from [10.72.13.133] (ovpn-13-133.pek2.redhat.com [10.72.13.133]) by smtp.corp.redhat.com (Postfix) with ESMTP id C93895D9D3; Wed, 4 Nov 2020 01:58:11 +0000 (UTC) Subject: Re: [PATCH 2/2] 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: <1604043944-4897-1-git-send-email-si-wei.liu@oracle.com> <1604043944-4897-2-git-send-email-si-wei.liu@oracle.com> <42fe6ef3-90f6-ddb9-f206-e60c1e98c301@redhat.com> <5FA1FE87.4050909@oracle.com> <5FA1FF1B.1000303@oracle.com> From: Jason Wang Message-ID: <328b6e09-7393-00d8-54d9-aac508b3016e@redhat.com> Date: Wed, 4 Nov 2020 09:58:09 +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: <5FA1FF1B.1000303@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 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/4 上午9:08, si-wei liu wrote: > > On 11/3/2020 5:06 PM, si-wei liu wrote: >> >> On 11/3/2020 5:00 AM, Jason Wang wrote: >>> >>> On 2020/10/30 下午3:45, 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 >>>> --- >>>>   drivers/vhost/vdpa.c | 64 >>>> +++++++++++++++++++++++++++++++++++++--------------- >>>>   1 file changed, 46 insertions(+), 18 deletions(-) >>>> >>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c >>>> index b6d9016..8da8558 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 +611,64 @@ 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) >>>>                       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 +676,22 @@ static int >>>> vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, >>>>                    map_pfn << PAGE_SHIFT, msg->perm); >>>>   out: >>>>       if (ret) { >>>> +        if (nchunks && last_pfn) { >>>> +            unsigned long pfn; >>>> + >>>> +            /* >>>> +             * Unpin the outstanding pages which are unmapped. >>>> +             * Mapped pages are accounted in vdpa_map(), thus >>>> +             * 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); >>> >>> >>> I want to know what's wrong with current code. >>> >>> We call vhost_vdpa_unmap() on error which calls >>> vhost_vdpa_iotlb_unmap() that will unpin and reduce the pinned_vm. >> Think about the case where vhost_vdpa_map() fails in the middle after >> making a few successful ones. In the current code, the >> vhost_vdpa_iotlb_unmap() unpins what had been mapped, but does not >> unpin those that have not yet been mapped. These outstanding pinned >> pages will be leaked after leaving the vhost_vdpa_map() function. > Typo: ... leaving the vhost_vdpa_process_iotlb_update() function. >> >> Also, the subtraction accounting at the end of the function is >> incorrect in that case: @npages is deduced by @pinned in each >> iteration. That's why I moved the accounting to vhost_vdpa_map() to >> be symmetric with vhost_vdpa_unmap(). >> I see, then I wonder if it would have more easy to read code if we do (un)pinning/accouting only in vhost_vdpa_map()/vhost_vdpa_unmap()? Thanks >> >> -Siwei >>> >>> Thanks >>> >>> >>>> -        atomic64_sub(npages, &dev->mm->pinned_vm); >>>>       } >>>> +unlock: >>>>       mmap_read_unlock(dev->mm); >>>> +free: >>>>       free_page((unsigned long)page_list); >>>>       return ret; >>>>   } >>> >> >