From: "Burakov, Anatoly" <anatoly.burakov@intel.com> To: Nithin Dabilpuram <nithind1988@gmail.com> Cc: Jerin Jacob <jerinj@marvell.com>, dev@dpdk.org, stable@dpdk.org Subject: Re: [dpdk-stable] [dpdk-dev] [EXT] Re: [PATCH 2/2] vfio: fix partial DMA unmapping for VFIO type1 Date: Sat, 17 Oct 2020 17:14:55 +0100 Message-ID: <4deaf00f-02d3-15b3-2ebe-4a2becc89251@intel.com> (raw) In-Reply-To: <20201016071015.GA22749@gmail.com> 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 >>> <anatoly.burakov@intel.com> 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= >>>> >>>> <snip> >>>> >>>>>>> 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? >> >> -- >> Thanks, >> Anatoly -- Thanks, Anatoly
next prev parent reply other threads:[~2020-10-17 16:15 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <20201012081106.10610-1-ndabilpuram@marvell.com> 2020-10-12 8:11 ` [dpdk-stable] " Nithin Dabilpuram 2020-10-14 15:07 ` Burakov, Anatoly 2020-10-15 6:09 ` [dpdk-stable] [EXT] " Nithin Dabilpuram 2020-10-15 10:00 ` Burakov, Anatoly 2020-10-15 11:38 ` Nithin Dabilpuram 2020-10-15 11:50 ` Nithin Dabilpuram 2020-10-15 11:57 ` [dpdk-stable] [dpdk-dev] " Nithin Dabilpuram 2020-10-15 15:10 ` Burakov, Anatoly 2020-10-16 7:10 ` Nithin Dabilpuram 2020-10-17 16:14 ` Burakov, Anatoly [this message] 2020-10-19 9:43 ` Nithin Dabilpuram 2020-10-22 12:13 ` Nithin Dabilpuram 2020-10-28 13:04 ` Burakov, Anatoly 2020-10-28 14:17 ` Nithin Dabilpuram 2020-10-28 16:07 ` Burakov, Anatoly 2020-10-28 16:31 ` Nithin Dabilpuram [not found] ` <20201105090423.11954-1-ndabilpuram@marvell.com> 2020-11-05 9:04 ` [dpdk-stable] [PATCH v2 1/3] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2020-11-05 9:04 ` [dpdk-stable] [PATCH v2 2/3] vfio: fix DMA mapping granularity for type1 iova as va Nithin Dabilpuram 2020-11-10 14:04 ` Burakov, Anatoly 2020-11-10 14:22 ` [dpdk-stable] [dpdk-dev] " Burakov, Anatoly 2020-11-10 14:17 ` [dpdk-stable] " Burakov, Anatoly 2020-11-11 5:08 ` [dpdk-stable] [dpdk-dev] " Nithin Dabilpuram 2020-11-11 10:00 ` Burakov, Anatoly [not found] ` <20201201193302.28131-1-ndabilpuram@marvell.com> 2020-12-01 19:32 ` [dpdk-stable] [PATCH v3 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2020-12-01 19:33 ` [dpdk-stable] [PATCH v3 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram [not found] ` <20201202054647.3449-1-ndabilpuram@marvell.com> 2020-12-02 5:46 ` [dpdk-stable] [PATCH v4 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2020-12-02 18:36 ` David Christensen 2020-12-02 5:46 ` [dpdk-stable] [PATCH v4 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram 2020-12-02 18:38 ` David Christensen [not found] ` <20201214081935.23577-1-ndabilpuram@marvell.com> 2020-12-14 8:19 ` [dpdk-stable] [PATCH v5 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2020-12-14 8:19 ` [dpdk-stable] [PATCH v5 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram [not found] ` <20201217190604.29803-1-ndabilpuram@marvell.com> 2020-12-17 19:06 ` [dpdk-stable] [PATCH v6 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2020-12-17 19:06 ` [dpdk-stable] [PATCH v6 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram [not found] ` <20210112173923.30320-1-ndabilpuram@marvell.com> 2021-01-12 17:39 ` [dpdk-stable] [PATCH v7 1/3] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2021-01-12 17:39 ` [dpdk-stable] [PATCH v7 2/3] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram [not found] ` <20210115073243.7025-1-ndabilpuram@marvell.com> 2021-01-15 7:32 ` [dpdk-stable] [PATCH v8 1/3] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram 2021-03-05 7:50 ` David Marchand 2021-03-05 13:54 ` Burakov, Anatoly 2021-03-05 15:50 ` [dpdk-stable] [dpdk-dev] " Nithin Dabilpuram 2021-01-15 7:32 ` [dpdk-stable] [PATCH v8 2/3] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram 2021-01-15 7:32 ` [dpdk-stable] [PATCH v8 3/3] test: change external memory test to use system page sz Nithin Dabilpuram 2021-02-11 11:21 ` Burakov, Anatoly
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