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definitions=main-2011040004 Cc: virtualization@lists.linux-foundation.org, boris.ostrovsky@oracle.com, linux-kernel@vger.kernel.org X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" Ck9uIDExLzMvMjAyMCA1OjAwIEFNLCBKYXNvbiBXYW5nIHdyb3RlOgo+Cj4gT24gMjAyMC8xMC8z MCDkuIvljYgzOjQ1LCBTaS1XZWkgTGl1IHdyb3RlOgo+PiBQaW5uZWQgcGFnZXMgYXJlIG5vdCBw cm9wZXJseSBhY2NvdW50ZWQgcGFydGljdWxhcmx5IHdoZW4KPj4gbWFwcGluZyBlcnJvciBvY2N1 cnMgb24gSU9UTEIgdXBkYXRlLiBDbGVhbiB1cCBkYW5nbGluZwo+PiBwaW5uZWQgcGFnZXMgZm9y IHRoZSBlcnJvciBwYXRoLgo+Pgo+PiBUaGUgbWVtb3J5IHVzYWdlIGZvciBib29ra2VlcGluZyBw aW5uZWQgcGFnZXMgaXMgcmV2ZXJ0ZWQKPj4gdG8gd2hhdCBpdCB3YXMgYmVmb3JlOiBvbmx5IG9u 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Wed, 04 Nov 2020 01:06:18 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id 0A416GW7001902; Wed, 4 Nov 2020 01:06:16 GMT Received: from [10.159.249.36] (/10.159.249.36) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 03 Nov 2020 17:06:16 -0800 Message-ID: <5FA1FE87.4050909@oracle.com> Date: Tue, 03 Nov 2020 17:06:15 -0800 From: si-wei liu Organization: Oracle Corporation User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: Jason Wang , 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 Subject: Re: [PATCH 2/2] vhost-vdpa: fix page pinning leakage in error path (rework) 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> In-Reply-To: <42fe6ef3-90f6-ddb9-f206-e60c1e98c301@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9794 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 suspectscore=2 mlxscore=0 bulkscore=0 malwarescore=0 mlxlogscore=999 phishscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011040004 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9794 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 adultscore=0 malwarescore=0 mlxscore=0 suspectscore=2 clxscore=1015 priorityscore=1501 impostorscore=0 spamscore=0 lowpriorityscore=0 mlxlogscore=999 phishscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011040004 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. 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(). -Siwei > > Thanks > > >> - atomic64_sub(npages, &dev->mm->pinned_vm); >> } >> +unlock: >> mmap_read_unlock(dev->mm); >> +free: >> free_page((unsigned long)page_list); >> return ret; >> } >