From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38397) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bpo4G-0004l8-SC for qemu-devel@nongnu.org; Thu, 29 Sep 2016 23:00:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bpo4A-0000gE-VQ for qemu-devel@nongnu.org; Thu, 29 Sep 2016 23:00:55 -0400 Received: from mga04.intel.com ([192.55.52.120]:29658) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bpo4A-0000g6-PL for qemu-devel@nongnu.org; Thu, 29 Sep 2016 23:00:50 -0400 Message-ID: <57EDD4CF.2080806@intel.com> Date: Fri, 30 Sep 2016 10:58:23 +0800 From: Jike Song MIME-Version: 1.0 References: <1472097235-6332-1-git-send-email-kwankhede@nvidia.com> <1472097235-6332-4-git-send-email-kwankhede@nvidia.com> <57EC79B3.2060305@intel.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v7 3/4] vfio iommu: Add support for mediated devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kirti Wankhede Cc: alex.williamson@redhat.com, pbonzini@redhat.com, kraxel@redhat.com, cjia@nvidia.com, qemu-devel@nongnu.org, kvm@vger.kernel.org, kevin.tian@intel.com, bjsdjshi@linux.vnet.ibm.com, "Xiao, Guangrong" On 09/29/2016 11:06 PM, Kirti Wankhede wrote: > > > On 9/29/2016 7:47 AM, Jike Song wrote: >> +Guangrong >> >> On 08/25/2016 11:53 AM, Kirti Wankhede wrote: > > ... > >>> +static long vfio_iommu_type1_pin_pages(void *iommu_data, >>> + unsigned long *user_pfn, >>> + long npage, int prot, >>> + unsigned long *phys_pfn) >>> +{ >>> + struct vfio_iommu *iommu = iommu_data; >>> + struct vfio_domain *domain; >>> + int i, j, ret; >>> + long retpage; >>> + unsigned long remote_vaddr; >>> + unsigned long *pfn = phys_pfn; >>> + struct vfio_dma *dma; >>> + bool do_accounting = false; >>> + >>> + if (!iommu || !user_pfn || !phys_pfn) >>> + return -EINVAL; >>> + >>> + mutex_lock(&iommu->lock); >>> + >>> + if (!iommu->local_domain) { >>> + ret = -EINVAL; >>> + goto pin_done; >>> + } >>> + >>> + domain = iommu->local_domain; >>> + >>> + /* >>> + * If iommu capable domain exist in the container then all pages are >>> + * already pinned and accounted. Accouting should be done if there is no >>> + * iommu capable domain in the container. >>> + */ >>> + do_accounting = !IS_IOMMU_CAPABLE_DOMAIN_IN_CONTAINER(iommu); >>> + >>> + for (i = 0; i < npage; i++) { >>> + struct vfio_pfn *p; >>> + dma_addr_t iova; >>> + >>> + iova = user_pfn[i] << PAGE_SHIFT; >>> + >>> + dma = vfio_find_dma(iommu, iova, 0); >>> + if (!dma) { >>> + ret = -EINVAL; >>> + goto pin_unwind; >>> + } >>> + >>> + remote_vaddr = dma->vaddr + iova - dma->iova; >>> + >>> + retpage = __vfio_pin_pages_local(domain, remote_vaddr, prot, >>> + &pfn[i], do_accounting); >> >> Hi Kirti, >> >> Here you call __vfio_pin_pages_local() > vaddr_get_pfn() > GUP regardless >> whether the vaddr already pinned or not. That probably means, if the caller >> calls vfio_pin_pages() with a GPA for multiple times, you get memory leaks. >> >> GUP always increases the page refcnt. >> >> FWIW, I would like to have the pfn_list_lock implemented with key == iova, >> so you can always try to find the PFN for a given iova, and pin it only if >> not found. >> > > I didn't get how there would be a memory leak. > > Right, GUP increases refcnt, so if vfio_pin_pages() is called for > multiple types for same GPA, refcnt would be incremented. In > vfio_iommu_type1_pin_pages() pinned pages list is maintained with > ref_count. If pfn is already in list, ref_count is incremented and same > is used while unpining pages. > Let's have a close look at vfio_unpin_pfn: static int vfio_unpin_pfn(struct vfio_domain *domain, struct vfio_pfn *vpfn, bool do_accounting) { __vfio_unpin_pages_for_mdev(domain, vpfn->pfn, vpfn->prot, do_accounting); if (atomic_dec_and_test(&vpfn->ref_count)) vfio_remove_from_pfn_list(domain, vpfn); return 1; } Here you didn't call __vfio_unpin_pages_for_mdev -- thereby put_page -- for vpfn->ref_count times. If page->_refcount increased by GUP for (N) times, here you only set it back to (N-1). -- Thanks, Jike