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 ? > > -- > Thanks, > Anatoly
