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.bura...@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. > */ > > > > > > > > > > > > -- > > > > Thanks, > > > > Anatoly > > > > > > -- > > Thanks, > > Anatoly
