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 A29DDA04DD; Wed, 28 Oct 2020 14:04:43 +0100 (CET) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 849AFCABF; Wed, 28 Oct 2020 14:04:38 +0100 (CET) Received: from mga14.intel.com (mga14.intel.com [192.55.52.115]) by dpdk.org (Postfix) with ESMTP id 7DA0DCAA2; Wed, 28 Oct 2020 14:04:35 +0100 (CET) IronPort-SDR: ybstgAXBNy6uaP9yFWQdlnVn92ad3jGZoWA/mssf1VyRv4f2ZQeVzsCbCMOWOS1IK5sxcfNQuf EkP+iREotZgg== X-IronPort-AV: E=McAfee;i="6000,8403,9787"; a="167472158" X-IronPort-AV: E=Sophos;i="5.77,426,1596524400"; d="scan'208";a="167472158" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Oct 2020 06:04:33 -0700 IronPort-SDR: MgU76D2g0qZPw7ebgzM3D22pxfcH8R8AqFIG6KbACwhnwI2jsATYLnU4yaDxa8r8RUq7axM5uQ 9vJ6cEX48kqw== X-IronPort-AV: E=Sophos;i="5.77,426,1596524400"; d="scan'208";a="536223214" Received: from aburakov-mobl.ger.corp.intel.com (HELO [10.213.193.36]) ([10.213.193.36]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 28 Oct 2020 06:04:32 -0700 To: Nithin Dabilpuram Cc: Jerin Jacob , dev@dpdk.org, stable@dpdk.org References: <20201012081106.10610-1-ndabilpuram@marvell.com> <20201012081106.10610-3-ndabilpuram@marvell.com> <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> From: "Burakov, Anatoly" Message-ID: <8cd0fd55-1af6-543d-50c1-80c5f4883550@intel.com> Date: Wed, 28 Oct 2020 13:04:26 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [EXT] Re: [PATCH 2/2] vfio: fix partial DMA unmapping for VFIO type1 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 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. -- Thanks, Anatoly