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[79.176.44.197]) by smtp.gmail.com with ESMTPSA id i11sm3746755wro.85.2020.11.25.01.30.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Nov 2020 01:30:14 -0800 (PST) Date: Wed, 25 Nov 2020 04:30:11 -0500 From: "Michael S. Tsirkin" To: Si-Wei Liu Cc: jasowang@redhat.com, lingshan.zhu@intel.com, joao.m.martins@oracle.com, boris.ostrovsky@oracle.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Subject: Re: [PATCH v3] vhost-vdpa: fix page pinning leakage in error path (rework) Message-ID: <20201125042834-mutt-send-email-mst@kernel.org> References: <1604618793-4681-1-git-send-email-si-wei.liu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1604618793-4681-1-git-send-email-si-wei.liu@oracle.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Nov 05, 2020 at 06:26:33PM -0500, 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 Not sure which tree this is against, I had to apply this with minor tweaks. Pls take a look at the vhost tree and let me know whether it looks ok to you. > --- > Changes in v3: > - Turn explicit last_pfn check to a WARN_ON() (Jason) > > Changes in v2: > - Drop the reversion patch > - Fix unhandled page leak towards the end of page_list > > drivers/vhost/vdpa.c | 80 ++++++++++++++++++++++++++++++++++++++++------------ > 1 file changed, 62 insertions(+), 18 deletions(-) > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c > index b6d9016..5b13dfd 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); > 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 +687,27 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v, > map_pfn << PAGE_SHIFT, msg->perm); > out: > if (ret) { > + if (nchunks) { > + 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(). > + */ > + WARN_ON(!last_pfn); > + 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; > } > -- > 1.8.3.1