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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-dev] [EXT] Re: [PATCH 2/2] vfio: fix partial DMA unmapping for VFIO type1
Date: Sat, 17 Oct 2020 17:14:55 +0100	[thread overview]
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

  reply	other threads:[~2020-10-17 16:15 UTC|newest]

Thread overview: 81+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-12  8:11 [dpdk-dev] [PATCH 0/2] fix issue with partial DMA unmap Nithin Dabilpuram
2020-10-12  8:11 ` [dpdk-dev] [PATCH 1/2] test: add test case to validate VFIO DMA map/unmap Nithin Dabilpuram
2020-10-14 14:39   ` Burakov, Anatoly
2020-10-15  9:54     ` [dpdk-dev] [EXT] " Nithin Dabilpuram
2020-10-12  8:11 ` [dpdk-dev] [PATCH 2/2] vfio: fix partial DMA unmapping for VFIO type1 Nithin Dabilpuram
2020-10-14 15:07   ` Burakov, Anatoly
2020-10-15  6:09     ` [dpdk-dev] [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         ` 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
2020-11-05  9:04 ` [dpdk-dev] [PATCH v2 0/3] fix issue with partial DMA unmap Nithin Dabilpuram
2020-11-05  9:04   ` [dpdk-dev] [PATCH v2 1/3] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram
2020-11-05  9:04   ` [dpdk-dev] [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       ` Burakov, Anatoly
2020-11-10 14:17     ` Burakov, Anatoly
2020-11-11  5:08       ` Nithin Dabilpuram
2020-11-11 10:00         ` Burakov, Anatoly
2020-11-05  9:04   ` [dpdk-dev] [PATCH v2 3/3] test: add test case to validate VFIO DMA map/unmap Nithin Dabilpuram
2020-12-01 19:32 ` [dpdk-dev] [PATCH v3 0/4] fix issue with partial DMA unmap Nithin Dabilpuram
2020-12-01 19:32   ` [dpdk-dev] [PATCH v3 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram
2020-12-01 19:33   ` [dpdk-dev] [PATCH v3 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram
2020-12-01 19:33   ` [dpdk-dev] [PATCH v3 3/4] test: add test case to validate VFIO DMA map/unmap Nithin Dabilpuram
2020-12-01 19:33   ` [dpdk-dev] [PATCH v3 4/4] test: change external memory test to use system page sz Nithin Dabilpuram
2020-12-01 23:23     ` David Christensen
2020-12-02  5:40       ` Nithin Dabilpuram
2020-12-02  5:46 ` [dpdk-dev] [PATCH v4 0/4] fix issue with partial DMA unmap Nithin Dabilpuram
2020-12-02  5:46   ` [dpdk-dev] [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-dev] [PATCH v4 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram
2020-12-02 18:38     ` David Christensen
2020-12-02  5:46   ` [dpdk-dev] [PATCH v4 3/4] test: add test case to validate VFIO DMA map/unmap Nithin Dabilpuram
2020-12-02 19:23     ` David Christensen
2020-12-03  7:14       ` Nithin Dabilpuram
2020-12-14  8:24         ` Nithin Dabilpuram
2020-12-02  5:46   ` [dpdk-dev] [PATCH v4 4/4] test: change external memory test to use system page sz Nithin Dabilpuram
2020-12-14  8:19 ` [dpdk-dev] [PATCH v5 0/4] fix issue with partial DMA unmap Nithin Dabilpuram
2020-12-14  8:19   ` [dpdk-dev] [PATCH v5 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram
2020-12-14  8:19   ` [dpdk-dev] [PATCH v5 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram
2020-12-14  8:19   ` [dpdk-dev] [PATCH v5 3/4] test: add test case to validate VFIO DMA map/unmap Nithin Dabilpuram
2020-12-14  8:19   ` [dpdk-dev] [PATCH v5 4/4] test: change external memory test to use system page sz Nithin Dabilpuram
2020-12-17 19:06 ` [dpdk-dev] [PATCH v6 0/4] fix issue with partial DMA unmap Nithin Dabilpuram
2020-12-17 19:06   ` [dpdk-dev] [PATCH v6 1/4] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram
2020-12-17 19:06   ` [dpdk-dev] [PATCH v6 2/4] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram
2020-12-17 19:06   ` [dpdk-dev] [PATCH v6 3/4] test: add test case to validate VFIO DMA map/unmap Nithin Dabilpuram
2020-12-17 19:10     ` Nithin Dabilpuram
2021-01-05 19:33       ` David Christensen
2021-01-06  8:40         ` Nithin Dabilpuram
2021-01-06 21:20           ` David Christensen
2020-12-17 19:06   ` [dpdk-dev] [PATCH v6 4/4] test: change external memory test to use system page sz Nithin Dabilpuram
2020-12-23  5:13   ` [dpdk-dev] [PATCH v6 0/4] fix issue with partial DMA unmap Nithin Dabilpuram
2021-01-04 22:29     ` David Christensen
2021-01-12 17:39 ` [dpdk-dev] [PATCH v7 0/3] " Nithin Dabilpuram
2021-01-12 17:39   ` [dpdk-dev] [PATCH v7 1/3] vfio: revert changes for map contiguous areas in one go Nithin Dabilpuram
2021-01-12 17:39   ` [dpdk-dev] [PATCH v7 2/3] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram
2021-01-12 17:39   ` [dpdk-dev] [PATCH v7 3/3] test: change external memory test to use system page sz Nithin Dabilpuram
2021-01-14 16:30     ` David Marchand
2021-01-15  6:57       ` Nithin Dabilpuram
2021-01-15  7:32 ` [dpdk-dev] [PATCH v8 0/3] fix issue with partial DMA unmap Nithin Dabilpuram
2021-01-15  7:32   ` [dpdk-dev] [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         ` Nithin Dabilpuram
2021-04-01 11:27           ` Burakov, Anatoly
2021-01-15  7:32   ` [dpdk-dev] [PATCH v8 2/3] vfio: fix DMA mapping granularity for type1 IOVA as VA Nithin Dabilpuram
2021-01-15  7:32   ` [dpdk-dev] [PATCH v8 3/3] test: change external memory test to use system page sz Nithin Dabilpuram
2021-02-11 11:21     ` Burakov, Anatoly
2021-02-16 13:14   ` [dpdk-dev] [PATCH v8 0/3] fix issue with partial DMA unmap Burakov, Anatoly
2021-02-22  9:41     ` Nithin Dabilpuram
2021-02-22 10:06       ` David Marchand
2021-03-01 12:13   ` David Marchand

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