From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 2F58BA04DD for ; Wed, 28 Oct 2020 15:17:30 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id EC927CB6B; Wed, 28 Oct 2020 15:17:28 +0100 (CET) Received: from mail-pg1-f194.google.com (mail-pg1-f194.google.com [209.85.215.194]) by dpdk.org (Postfix) with ESMTP id 9891DCB19; Wed, 28 Oct 2020 15:17:23 +0100 (CET) Received: by mail-pg1-f194.google.com with SMTP id r10so2851771pgb.10; Wed, 28 Oct 2020 07:17:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=MkN7CJesrqvBAKQOLvaznOS/OVJhQFnR6c2U2PMnOJU=; b=qEs3q+0J1m8Hp5+hKuDzuHFov5T079Uux97TP9iYR5DUve+T9HFfFWO9JL2CrlW0Sj jw69yItPTO8XX+fJyWa6ePcVjROunGL3MTEdTtEfxCIw5VNu/OIMEmdBVZKVj2ItTGVp HV05yqODE8uWhq3lpx8LAjVyiUQ5gjM8DEVU86T3lg/n6COuCrkRCiSsey20qMVmXC2C Eo51XOvvpJyFnVxZ1R1K/irq3ChjKiGPa/xP3BUbily+QMCmwmt5q0/AYPexlXuUIb8O Tdu4UscsqTgYRonry63hZIiQMT8LgMmuyAXFRrJByO5B9a5TQIt0bvaxsMiDmqD28IKD 09xw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=MkN7CJesrqvBAKQOLvaznOS/OVJhQFnR6c2U2PMnOJU=; b=bBsHkI0ZLVLp2AuLCG+kAa0TrraJQ8vnPdG6B4U2R0p5JsMQx0AgEzUpYYdml+TO/L XqcsIKNNJ1oxeD0KcFo4FZR/gj2X0ARWm5+IJhdht7RGJwUVw8PRtUja5UFXGMYxCUU1 N1ETQrXcQRYEvLM6nJIXRgNtN7CDFu2AEFn9r5QWZ6dOpiQLpsGtxx7mwQIaLIFXO6Uq t9Ct/tEmplDms4+hJZQrUgOITpZwiJo7XbW/kVFoZBVWltQ9xQzDUf/OdDGEW9J47J9T qNC2DP/xKlY0RiDqCbmMhMehEpF7tRrBii7gir4BOH+CA2OjqxjP4JtBcME0tP8q7CgC JP0A== X-Gm-Message-State: AOAM532wAqkOt0XY5yzbHzDOZDh3pMvABXaKFqHPTWIMtYi9hNa7p0wT O+XUq7iYthMLIUbTZ/3fWGE= X-Google-Smtp-Source: ABdhPJzghvTlLDO2HrAQ051wVBTbxS3aVhyslzbG7Q238Ftr1u9iwKa7RhYUUg/tS/pyfQmmIsAj7Q== X-Received: by 2002:a62:3782:0:b029:15d:2c3e:ca14 with SMTP id e124-20020a6237820000b029015d2c3eca14mr7970462pfa.38.1603894641625; Wed, 28 Oct 2020 07:17:21 -0700 (PDT) Received: from gmail.com ([1.6.215.26]) by smtp.gmail.com with ESMTPSA id c10sm6165026pfc.196.2020.10.28.07.17.19 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 28 Oct 2020 07:17:21 -0700 (PDT) Date: Wed, 28 Oct 2020 19:47:16 +0530 From: Nithin Dabilpuram To: "Burakov, Anatoly" Cc: Jerin Jacob , dev@dpdk.org, stable@dpdk.org Message-ID: References: <05afb7f5-96bf-dffd-15dd-2024586f7290@intel.com> <20201015060914.GA32207@outlook.office365.com> <66b61bda-03a8-d4c4-af9f-0f90a6ef956d@intel.com> <20201016071015.GA22749@gmail.com> <4deaf00f-02d3-15b3-2ebe-4a2becc89251@intel.com> <8cd0fd55-1af6-543d-50c1-80c5f4883550@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8cd0fd55-1af6-543d-50c1-80c5f4883550@intel.com> Subject: Re: [dpdk-stable] [dpdk-dev] [EXT] Re: [PATCH 2/2] vfio: fix partial DMA unmapping for VFIO type1 X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org Sender: "stable" On Wed, Oct 28, 2020 at 01:04:26PM +0000, Burakov, Anatoly wrote: > On 22-Oct-20 1:13 PM, Nithin Dabilpuram wrote: > > Ping. > > > > On Mon, Oct 19, 2020 at 03:13:15PM +0530, Nithin Dabilpuram wrote: > > > On Sat, Oct 17, 2020 at 05:14:55PM +0100, Burakov, Anatoly wrote: > > > > On 16-Oct-20 8:10 AM, Nithin Dabilpuram wrote: > > > > > On Thu, Oct 15, 2020 at 04:10:31PM +0100, Burakov, Anatoly wrote: > > > > > > On 15-Oct-20 12:57 PM, Nithin Dabilpuram wrote: > > > > > > > On Thu, Oct 15, 2020 at 3:31 PM Burakov, Anatoly > > > > > > > wrote: > > > > > > > > > > > > > > > > On 15-Oct-20 7:09 AM, Nithin Dabilpuram wrote: > > > > > > > > > On Wed, Oct 14, 2020 at 04:07:10PM +0100, Burakov, Anatoly wrote: > > > > > > > > > > External Email > > > > > > > > > > > > > > > > > > > > ---------------------------------------------------------------------- > > > > > > > > > > On 12-Oct-20 9:11 AM, Nithin Dabilpuram wrote: > > > > > > > > > > > Partial unmapping is not supported for VFIO IOMMU type1 > > > > > > > > > > > by kernel. Though kernel gives return as zero, the unmapped size > > > > > > > > > > > returned will not be same as expected. So check for > > > > > > > > > > > returned unmap size and return error. > > > > > > > > > > > > > > > > > > > > > > For case of DMA map/unmap triggered by heap allocations, > > > > > > > > > > > maintain granularity of memseg page size so that heap > > > > > > > > > > > expansion and contraction does not have this issue. > > > > > > > > > > > > > > > > > > > > This is quite unfortunate, because there was a different bug that had to do > > > > > > > > > > with kernel having a very limited number of mappings available [1], as a > > > > > > > > > > result of which the page concatenation code was added. > > > > > > > > > > > > > > > > > > > > It should therefore be documented that the dma_entry_limit parameter should > > > > > > > > > > be adjusted should the user run out of the DMA entries. > > > > > > > > > > > > > > > > > > > > [1] https://urldefense.proofpoint.com/v2/url?u=https-3A__lore.kernel.org_lkml_155414977872.12780.13728555131525362206.stgit-40gimli.home_T_&d=DwICaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=FZ_tPCbgFOh18zwRPO9H0yDx8VW38vuapifdDfc8SFQ&m=3GMg-634_cdUCY4WpQPwjzZ_S4ckuMHOnt2FxyyjXMk&s=TJLzppkaDS95VGyRHX2hzflQfb9XLK0OiOszSXoeXKk&e= > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > RTE_LOG(ERR, EAL, " cannot clear DMA remapping, error %i (%s)\n", > > > > > > > > > > > errno, strerror(errno)); > > > > > > > > > > > return -1; > > > > > > > > > > > + } else if (dma_unmap.size != len) { > > > > > > > > > > > + RTE_LOG(ERR, EAL, " unexpected size %"PRIu64" of DMA " > > > > > > > > > > > + "remapping cleared instead of %"PRIu64"\n", > > > > > > > > > > > + (uint64_t)dma_unmap.size, len); > > > > > > > > > > > + rte_errno = EIO; > > > > > > > > > > > + return -1; > > > > > > > > > > > } > > > > > > > > > > > } > > > > > > > > > > > @@ -1853,6 +1869,12 @@ container_dma_unmap(struct vfio_config *vfio_cfg, uint64_t vaddr, uint64_t iova, > > > > > > > > > > > /* we're partially unmapping a previously mapped region, so we > > > > > > > > > > > * need to split entry into two. > > > > > > > > > > > */ > > > > > > > > > > > + if (!vfio_cfg->vfio_iommu_type->partial_unmap) { > > > > > > > > > > > + RTE_LOG(DEBUG, EAL, "DMA partial unmap unsupported\n"); > > > > > > > > > > > + rte_errno = ENOTSUP; > > > > > > > > > > > + ret = -1; > > > > > > > > > > > + goto out; > > > > > > > > > > > + } > > > > > > > > > > > > > > > > > > > > How would we ever arrive here if we never do more than 1 page worth of > > > > > > > > > > memory anyway? I don't think this is needed. > > > > > > > > > > > > > > > > > > container_dma_unmap() is called by user via rte_vfio_container_dma_unmap() > > > > > > > > > and when he maps we don't split it as we don't about his memory. > > > > > > > > > So if he maps multiple pages and tries to unmap partially, then we should fail. > > > > > > > > > > > > > > > > Should we map it in page granularity then, instead of adding this > > > > > > > > discrepancy between EAL and user mapping? I.e. instead of adding a > > > > > > > > workaround, how about we just do the same thing for user mem mappings? > > > > > > > > > > > > > > > In heap mapping's we map and unmap it at huge page granularity as we will always > > > > > > > maintain that. > > > > > > > > > > > > > > But here I think we don't know if user's allocation is huge page or > > > > > > > collection of system > > > > > > > pages. Only thing we can do here is map it at system page granularity which > > > > > > > could waste entries if he say really is working with hugepages. Isn't ? > > > > > > > > > > > > > > > > > > > Yeah we do. The API mandates the pages granularity, and it will check > > > > > > against page size and number of IOVA entries, so yes, we do enforce the fact > > > > > > that the IOVA addresses supplied by the user have to be page addresses. > > > > > > > > > > If I see rte_vfio_container_dma_map(), there is no mention of Huge page size > > > > > user is providing or we computing. He can call rte_vfio_container_dma_map() > > > > > with 1GB huge page or 4K system page. > > > > > > > > > > Am I missing something ? > > > > > > > > Are you suggesting that a DMA mapping for hugepage-backed memory will be > > > > made at system page size granularity? E.g. will a 1GB page-backed segment be > > > > mapped for DMA as a contiguous 4K-based block? > > > > > > I'm not suggesting anything. My only thought is how to solve below problem. > > > Say application does the following. > > > > > > #1 Allocate 1GB memory from huge page or some external mem. > > > #2 Do rte_vfio_container_dma_map(RTE_VFIO_DEFAULT_CONTAINER_FD, mem, mem, 1GB) > > > In linux/eal_vfio.c, we map it is as single VFIO DMA entry of 1 GB as we > > > don't know where this memory is coming from or backed by what. > > > #3 After a while call rte_vfio_container_dma_unmap(RTE_VFIO_DEFAULT_CONTAINER_FD, mem+4KB, mem+4KB, 4KB) > > > Though rte_vfio_container_dma_unmap() supports #3 by splitting entry as shown below, > > > In VFIO type1 iommu, #3 cannot be supported by current kernel interface. So how > > > can we allow #3 ? > > > > > > > > > static int > > > container_dma_unmap(struct vfio_config *vfio_cfg, uint64_t vaddr, uint64_t iova, > > > uint64_t len) > > > { > > > struct user_mem_map *map, *new_map = NULL; > > > struct user_mem_maps *user_mem_maps; > > > int ret = 0; > > > > > > user_mem_maps = &vfio_cfg->mem_maps; > > > rte_spinlock_recursive_lock(&user_mem_maps->lock); > > > > > > /* find our mapping */ > > > map = find_user_mem_map(user_mem_maps, vaddr, iova, len); > > > if (!map) { > > > RTE_LOG(ERR, EAL, "Couldn't find previously mapped region\n"); > > > rte_errno = EINVAL; > > > ret = -1; > > > goto out; > > > } > > > if (map->addr != vaddr || map->iova != iova || map->len != len) { > > > /* we're partially unmapping a previously mapped region, so we > > > * need to split entry into two. > > > */ > > Hi, > > Apologies, i was on vacation. > > Yes, I can see the problem now. Does VFIO even support non-system page > sizes? Like, if i allocated a 1GB page, would i be able to map *this page* > for DMA, as opposed to first 4K of this page? I suspect that the mapping > doesn't support page sizes other than the system page size. It does support mapping any multiple of system page size. See vfio/vfio_iommu_type1.c vfio_pin_map_dma(). Also ./driver-api/vfio.rst doesn't mention any such restrictions even in its example. Also my test case is passing so that confirms the behavior. > > -- > Thanks, > Anatoly