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 5053CC388F7 for ; Tue, 10 Nov 2020 03:28:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA16520721 for ; Tue, 10 Nov 2020 03:27:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="jKjvk18A" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730767AbgKJD16 (ORCPT ); Mon, 9 Nov 2020 22:27:58 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:26027 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729454AbgKJD15 (ORCPT ); Mon, 9 Nov 2020 22:27:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1604978875; 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=OdCoLTrBfFCRAJuNHfetWuIU7FDMdIZe8NhWrpGSAhw=; b=jKjvk18ADxfj2Qs/DK5MX87gT6ui+5oPiDA94VuBd2GrxCPdsrS4Sw2vIpY1ZURrSKDr8d n78VYnZARbkqcRfYxZNf84k7hgPfYiLPaOLX6CGC83PYcisU0rgVAM+x9IU4p9tnrBfsvI dqXes8k2KYGDlXQ6pgFM01+zFb6hb80= 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-509-pnvPGuLDMqikGu0rbBpPqg-1; Mon, 09 Nov 2020 22:27:51 -0500 X-MC-Unique: pnvPGuLDMqikGu0rbBpPqg-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id BE76C57207; Tue, 10 Nov 2020 03:27:49 +0000 (UTC) Received: from [10.72.13.94] (ovpn-13-94.pek2.redhat.com [10.72.13.94]) by smtp.corp.redhat.com (Postfix) with ESMTP id D89235C1D0; Tue, 10 Nov 2020 03:27:43 +0000 (UTC) Subject: Re: [PATCH v2] vhost-vdpa: fix page pinning leakage in error path (rework) To: si-wei liu , "Michael S. Tsirkin" Cc: lingshan.zhu@intel.com, 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> <64fb6179-c5ff-9552-381f-85b63e704057@redhat.com> <5FA9B823.9060609@oracle.com> <20201109173236-mutt-send-email-mst@kernel.org> <5FA9D725.3050906@oracle.com> From: Jason Wang Message-ID: <41804db9-27fe-5f5c-9d87-34fd380f3693@redhat.com> Date: Tue, 10 Nov 2020 11:27:42 +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: <5FA9D725.3050906@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 10.5.11.16 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/10 上午7:56, si-wei liu wrote: > > On 11/9/2020 2:42 PM, Michael S. Tsirkin wrote: >> On Mon, Nov 09, 2020 at 01:44:03PM -0800, si-wei liu wrote: >>> On 11/8/2020 7:21 PM, Jason Wang wrote: >>>> 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? >>> The current code has implicit assumption that nchunks != 0 infers >>> last_pfn >>> != 0. However, this assumption could break subject to code structure >>> changes >>> for eg. failure may occur after the increment of nchunks and before >>> the for >>> loop. I feel it'd be the best to capture this assumption with something >>> explicit. >>> >>> -Siwei >> if here isn't really an explicit way to document assumptions, >> it's a way to avoid assumptions :) > Agreed. I was referring to the v3 patch which had turned the defensive > coding to a WARN_ON(). I think I get you now. > >> A way to document assumptions is probably BUG_ON. > If you're fine with below checkpatch warning I can definitely convert > it to a BUG_ON: > > WARNING: Avoid crashing the kernel - try using WARN_ON & recovery code > rather than BUG() or BUG_ON() > > Let me know if I need to post a v4 for this nit. I will ack for V3. Thanks > > Thanks > -Siwei > > > >> >>>> 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; >>>>>>>    } >