From: Nithin Dabilpuram <nithind1988@gmail.com> To: "Burakov, Anatoly" <anatoly.burakov@intel.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: Wed, 28 Oct 2020 19:47:16 +0530 Message-ID: <X5l9bO5/+fyyt+qT@gmail.com> (raw) In-Reply-To: <8cd0fd55-1af6-543d-50c1-80c5f4883550@intel.com> 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 > > > > > > > <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? > > > > > > 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
next prev parent reply other threads:[~2020-10-28 14:17 UTC|newest] Thread overview: 72+ 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 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 [this message] 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 2021-01-15 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
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