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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 EB1E9C43331 for ; Tue, 31 Mar 2020 01:00:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BC35B2054F for ; Tue, 31 Mar 2020 01:00:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729299AbgCaBA2 (ORCPT ); Mon, 30 Mar 2020 21:00:28 -0400 Received: from mga06.intel.com ([134.134.136.31]:16561 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729019AbgCaBA2 (ORCPT ); Mon, 30 Mar 2020 21:00:28 -0400 IronPort-SDR: 40WpJL8NMSn2KmIzP4wpCyjS66p9tKBdrbVyeUBqIN8T2soyb/po5EgiWpTDqo2yoEgNvKmX8L j2SrF7FeW3aw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga004.jf.intel.com ([10.7.209.38]) by orsmga104.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 30 Mar 2020 18:00:27 -0700 IronPort-SDR: oQyiHOOyCQKq68piWWtpyULYgDUNtHhnnfV0fvwCAAaR3jQ50hSjCRHWqeezMUNPjoHshxePtu ml/V3Rm9qw/w== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,326,1580803200"; d="scan'208";a="395319595" Received: from joy-optiplex-7040.sh.intel.com (HELO joy-OptiPlex-7040) ([10.239.13.16]) by orsmga004.jf.intel.com with ESMTP; 30 Mar 2020 18:00:20 -0700 Date: Mon, 30 Mar 2020 20:50:47 -0400 From: Yan Zhao To: Alex Williamson Cc: Kirti Wankhede , "cjia@nvidia.com" , "Tian, Kevin" , "Yang, Ziye" , "Liu, Changpeng" , "Liu, Yi L" , "mlevitsk@redhat.com" , "eskultet@redhat.com" , "cohuck@redhat.com" , "dgilbert@redhat.com" , "jonathan.davies@nutanix.com" , "eauger@redhat.com" , "aik@ozlabs.ru" , "pasic@linux.ibm.com" , "felipe@nutanix.com" , "Zhengxiao.zx@Alibaba-inc.com" , "shuangtai.tst@alibaba-inc.com" , "Ken.Xue@amd.com" , "Wang, Zhi A" , "qemu-devel@nongnu.org" , "kvm@vger.kernel.org" Subject: Re: [PATCH v16 Kernel 4/7] vfio iommu: Implementation of ioctl for dirty pages tracking. Message-ID: <20200331005046.GB6631@joy-OptiPlex-7040> Reply-To: Yan Zhao References: <1585084732-18473-1-git-send-email-kwankhede@nvidia.com> <20200325021135.GB20109@joy-OptiPlex-7040> <33d38629-aeaf-1c30-26d4-958b998620b0@nvidia.com> <20200327003055.GB26419@joy-OptiPlex-7040> <20200330032437.GD30683@joy-OptiPlex-7040> <20200330235131.GB6478@joy-OptiPlex-7040> <20200330185347.58b1ab93@x1.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200330185347.58b1ab93@x1.home> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, Mar 31, 2020 at 08:53:47AM +0800, Alex Williamson wrote: > On Mon, 30 Mar 2020 19:51:31 -0400 > Yan Zhao wrote: > > > On Mon, Mar 30, 2020 at 09:49:21PM +0800, Kirti Wankhede wrote: > > > > > > > > > On 3/30/2020 8:54 AM, Yan Zhao wrote: > > > > On Fri, Mar 27, 2020 at 01:28:13PM +0800, Kirti Wankhede wrote: > > > >> Hit send button little early. > > > >> > > > >> > > > > >> > I checked v12, it's not like what I said. > > > >> > In v12, bitmaps are generated per vfio_dma, and combination of the > > > >> > bitmaps are required in order to generate a big bitmap suiting for dirty > > > >> > query. It can cause problem when offset not aligning. > > > >> > But what I propose here is to generate an rb tree orthogonal to the tree > > > >> > of vfio_dma. > > > >> > > > > >> > as to CPU cycles saving, I don't think iterating/translating page by page > > > >> > would achieve that purpose. > > > >> > > > > >> > > > >> Instead of creating one extra rb tree for dirty pages tracking in v10 > > > >> tried to use dma->pfn_list itself, we tried changes in v10, v11 and v12, > > > >> latest version is evolved version with best possible approach after > > > >> discussion. Probably, go through v11 as well. > > > >> https://patchwork.kernel.org/patch/11298335/ > > > >> > > > > I'm not sure why all those previous implementations are bound to > > > > vfio_dma. for vIOMMU on, in most cases, a vfio_dma is only for a page, > > > > so generating a one-byte bitmap for a single page in each vfio_dma ? > > > > is it possible to creating one extra rb tree to keep dirty ranges, and > > > > one fixed length kernel bitmap whose content is generated on query, > > > > serving as a bouncing buffer for copy_to_user > > > > > > > > > > One fixed length? what should be fixed value? then isn't it better to > > > fix the size to dma->size? > > > > > > This is also to prevent DoS attack, user space application can query a > > > very large range. > > > > > > >> > > > >> On 3/27/2020 6:00 AM, Yan Zhao wrote: > > > >>> On Fri, Mar 27, 2020 at 05:39:01AM +0800, Kirti Wankhede wrote: > > > >>>> > > > >>>> > > > >>>> On 3/25/2020 7:41 AM, Yan Zhao wrote: > > > >>>>> On Wed, Mar 25, 2020 at 05:18:52AM +0800, Kirti Wankhede wrote: > > > >>>>>> VFIO_IOMMU_DIRTY_PAGES ioctl performs three operations: > > > >>>>>> - Start dirty pages tracking while migration is active > > > >>>>>> - Stop dirty pages tracking. > > > >>>>>> - Get dirty pages bitmap. Its user space application's responsibility to > > > >>>>>> copy content of dirty pages from source to destination during migration. > > > >>>>>> > > > >>>>>> To prevent DoS attack, memory for bitmap is allocated per vfio_dma > > > >>>>>> structure. Bitmap size is calculated considering smallest supported page > > > >>>>>> size. Bitmap is allocated for all vfio_dmas when dirty logging is enabled > > > >>>>>> > > > >>>>>> Bitmap is populated for already pinned pages when bitmap is allocated for > > > >>>>>> a vfio_dma with the smallest supported page size. Update bitmap from > > > >>>>>> pinning functions when tracking is enabled. When user application queries > > > >>>>>> bitmap, check if requested page size is same as page size used to > > > >>>>>> populated bitmap. If it is equal, copy bitmap, but if not equal, return > > > >>>>>> error. > > > >>>>>> > > > >>>>>> Signed-off-by: Kirti Wankhede > > > >>>>>> Reviewed-by: Neo Jia > > > >>>>>> --- > > > >>>>>> drivers/vfio/vfio_iommu_type1.c | 266 +++++++++++++++++++++++++++++++++++++++- > > > >>>>>> 1 file changed, 260 insertions(+), 6 deletions(-) > > > >>>>>> > > > >>>>>> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c > > > >>>>>> index 70aeab921d0f..874a1a7ae925 100644 > > > >>>>>> --- a/drivers/vfio/vfio_iommu_type1.c > > > >>>>>> +++ b/drivers/vfio/vfio_iommu_type1.c > > > >>>>>> @@ -71,6 +71,7 @@ struct vfio_iommu { > > > >>>>>> unsigned int dma_avail; > > > >>>>>> bool v2; > > > >>>>>> bool nesting; > > > >>>>>> + bool dirty_page_tracking; > > > >>>>>> }; > > > >>>>>> > > > >>>>>> struct vfio_domain { > > > >>>>>> @@ -91,6 +92,7 @@ struct vfio_dma { > > > >>>>>> bool lock_cap; /* capable(CAP_IPC_LOCK) */ > > > >>>>>> struct task_struct *task; > > > >>>>>> struct rb_root pfn_list; /* Ex-user pinned pfn list */ > > > >>>>>> + unsigned long *bitmap; > > > >>>>>> }; > > > >>>>>> > > > >>>>>> struct vfio_group { > > > >>>>>> @@ -125,7 +127,21 @@ struct vfio_regions { > > > >>>>>> #define IS_IOMMU_CAP_DOMAIN_IN_CONTAINER(iommu) \ > > > >>>>>> (!list_empty(&iommu->domain_list)) > > > >>>>>> > > > >>>>>> +#define DIRTY_BITMAP_BYTES(n) (ALIGN(n, BITS_PER_TYPE(u64)) / BITS_PER_BYTE) > > > >>>>>> + > > > >>>>>> +/* > > > >>>>>> + * Input argument of number of bits to bitmap_set() is unsigned integer, which > > > >>>>>> + * further casts to signed integer for unaligned multi-bit operation, > > > >>>>>> + * __bitmap_set(). > > > >>>>>> + * Then maximum bitmap size supported is 2^31 bits divided by 2^3 bits/byte, > > > >>>>>> + * that is 2^28 (256 MB) which maps to 2^31 * 2^12 = 2^43 (8TB) on 4K page > > > >>>>>> + * system. > > > >>>>>> + */ > > > >>>>>> +#define DIRTY_BITMAP_PAGES_MAX (uint64_t)(INT_MAX - 1) > > > >>>>>> +#define DIRTY_BITMAP_SIZE_MAX DIRTY_BITMAP_BYTES(DIRTY_BITMAP_PAGES_MAX) > > > >>>>>> + > > > >>>>>> static int put_pfn(unsigned long pfn, int prot); > > > >>>>>> +static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu); > > > >>>>>> > > > >>>>>> /* > > > >>>>>> * This code handles mapping and unmapping of user data buffers > > > >>>>>> @@ -175,6 +191,77 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old) > > > >>>>>> rb_erase(&old->node, &iommu->dma_list); > > > >>>>>> } > > > >>>>>> > > > >>>>>> + > > > >>>>>> +static int vfio_dma_bitmap_alloc(struct vfio_dma *dma, uint64_t pgsize) > > > >>>>>> +{ > > > >>>>>> + uint64_t npages = dma->size / pgsize; > > > >>>>>> + > > > > If pgsize > dma->size, npages = 0. > > > > wouldn't it cause problem? > > > > > > > > > > This patch-set supports bitmap for smallest supported page size, i.e. > > > PAGE_SIZE. vfio_dma_do_map() validates dma->size accordingly. So this > > > case will not happen. > > > > > as far as I know, qemu/kvm uses 4k as the unit for dirty page tracking. > > so why smallest iommu page size is used here? > > wouldn't it cause problem? > > If your concern is that the IOMMU supports sub-4K page sizes, see > vfio_pgsize_bitmap(). We actually only support PAGE_SIZE as our > minimum mapping unit, even if the IOMMU supports less, so PAGE_SIZE is > our lower bound. Thanks, if we always uses PAGE_SIZE, why not use PAGE_SIZE directly? or returning dirty bitmap unit (e.g. 1 << __ffs(vfio_pgsize_bitmap(iommu))) to QEMU in VFIO_IOMMU_DIRTY_PAGES_FLAG_START, so that qemu can do possible conversion if it's not the same unit that QEMU uses. Thanks Yan