On 1/29/2019 6:58 PM, jgli...@redhat.com wrote:
> Convert ODP to use HMM so that we can build on common infrastructure
> for different class of devices that want to mirror a process address
> space into a device. There is no functional changes.
Thanks for sending this patch. I think in general it is a good idea to
use a common infrastructure for ODP.
I have a couple of questions below.
> -static void ib_umem_notifier_invalidate_range_end(struct mmu_notifier *mn,
> - const struct mmu_notifier_range *range)
> -{
> - struct ib_ucontext_per_mm *per_mm =
> - container_of(mn, struct ib_ucontext_per_mm, mn);
> -
> - if (unlikely(!per_mm->active))
> - return;
> -
> - rbt_ib_umem_for_each_in_range(&per_mm->umem_tree, range->start,
> - range->end,
> - invalidate_range_end_trampoline, true,
> NULL);
> up_read(&per_mm->umem_rwsem);
> + return ret;
> }
Previously the code held the umem_rwsem between range_start and
range_end calls. I guess that was in order to guarantee that no device
page faults take reference to the pages being invalidated while the
invalidation is ongoing. I assume this is now handled by hmm instead,
correct?
> +
> +static uint64_t odp_hmm_flags[HMM_PFN_FLAG_MAX] = {
> + ODP_READ_BIT, /* HMM_PFN_VALID */
> + ODP_WRITE_BIT, /* HMM_PFN_WRITE */
> + ODP_DEVICE_BIT, /* HMM_PFN_DEVICE_PRIVATE */
It seems that the mlx5_ib code in this patch currently ignores the
ODP_DEVICE_BIT (e.g., in umem_dma_to_mtt). Is that okay? Or is it
handled implicitly by the HMM_PFN_SPECIAL case?
> @@ -327,9 +287,10 @@ void put_per_mm(struct ib_umem_odp *umem_odp)
> up_write(&per_mm->umem_rwsem);
>
> WARN_ON(!RB_EMPTY_ROOT(&per_mm->umem_tree.rb_root));
> - mmu_notifier_unregister_no_release(&per_mm->mn, per_mm->mm);
> + hmm_mirror_unregister(&per_mm->mirror);
> put_pid(per_mm->tgid);
> - mmu_notifier_call_srcu(&per_mm->rcu, free_per_mm);
> +
> + kfree(per_mm);
> }
Previously the per_mm struct was released through call srcu, but now it
is released immediately. Is it safe? I saw that hmm_mirror_unregister
calls mmu_notifier_unregister_no_release, so I don't understand what
prevents concurrently running invalidations from accessing the released
per_mm struct.
> @@ -578,11 +578,27 @@ static int pagefault_mr(struct mlx5_ib_dev *dev, struct
> mlx5_ib_mr *mr,
>
> next_mr:
> size = min_t(size_t, bcnt, ib_umem_end(&odp->umem) - io_virt);
> -
> page_shift = mr->umem->page_shift;
> page_mask = ~(BIT(page_shift) - 1);
> + off = (io_virt & (~page_mask));
> + size += (io_virt & (~page_mask));
> + io_virt = io_virt & page_mask;
> + off += (size & (~page_mask));
> + size = ALIGN(size, 1UL << page_shift);
> +
> + if (io_virt < ib_umem_start(&odp->umem))
> + return -EINVAL;
> +
> start_idx = (io_virt - (mr->mmkey.iova & page_mask)) >> page_shift;
>
> + if (odp_mr->per_mm == NULL || odp_mr->per_mm->mm == NULL)
> + return -ENOENT;
> +
> + ret = hmm_range_register(&range, odp_mr->per_mm->mm,
> + io_virt, io_virt + size, page_shift);
> + if (ret)
> + return ret;
> +
> if (prefetch && !downgrade && !mr->umem->writable) {
> /* prefetch with write-access must
> * be supported by the MR
Isn't there a mistake in the calculation of the variable size? Itis
first set to the size of the page fault range, but then you add the
virtual address, so I guess it is actually the range end. Then you pass
io_virt + size to hmm_range_register. Doesn't it double the size of the
range
> -void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp, u64 virt,
> - u64 bound)
> +void ib_umem_odp_unmap_dma_pages(struct ib_umem_odp *umem_odp,
> + u64 virt, u64 bound)
> {
> + struct device *device = umem_odp->umem.context->device->dma_device;
> struct ib_umem *umem = &umem_odp->umem;
> - int idx;
> - u64 addr;
> - struct ib_device *dev = umem->context->device;
> + unsigned long idx, page_mask;
> + struct hmm_range range;
> + long ret;
> +
> + if (!umem->npages)
> + return;
> +
> + bound = ALIGN(bound, 1UL << umem->page_shift);
> + page_mask = ~(BIT(umem->page_shift) - 1);
> + virt &= page_mask;
>
> virt = max_t(u64, virt, ib_umem_start(umem));
> bound = min_t(u64, bound, ib_umem_end(umem));
> - /* Note that during the run of this function, the
> - * notifiers_count of the MR is > 0, preventing any racing
> - * faults from completion. We might be racing with other
> - * invalidations, so we must make sure we free each page only
> - * once. */
> +
> + idx = ((unsigned long)virt - ib_umem_start(umem)) >> PAGE_SHIFT;
> +
> + range.page_shift = umem->page_shift;
> + range.pfns = &umem_odp->pfns[idx];
> + range.pfn_shift = ODP_FLAGS_BITS;
> + range.values = odp_hmm_values;
> + range.flags = odp_hmm_flags;
> + range.start = virt;
> + range.end = bound;
> +
> mutex_lock(&umem_odp->umem_mutex);
> - for (addr = virt; addr < bound; addr += BIT(umem->page_shift)) {
> - idx = (addr - ib_umem_start(umem)) >> umem->page_shift;
> - if (umem_odp->page_list[idx]) {
> - struct page *page = umem_odp->page_list[idx];
> - dma_addr_t dma = umem_odp->dma_list[idx];
> - dma_addr_t dma_addr = dma & ODP_DMA_ADDR_MASK;
> -
> - WARN_ON(!dma_addr);
> -
> - ib_dma_unmap_page(dev, dma_addr, PAGE_SIZE,
> - DMA_BIDIRECTIONAL);
> - if (dma & ODP_WRITE_ALLOWED_BIT) {
> - struct page *head_page = compound_head(page);
> - /*
> - * set_page_dirty prefers being called with
> - * the page lock. However, MMU notifiers are
> - * called sometimes with and sometimes without
> - * the lock. We rely on the umem_mutex instead
> - * to prevent other mmu notifiers from
> - * continuing and allowing the page mapping to
> - * be removed.
> - */
> - set_page_dirty(head_page);
> - }
> - /* on demand pinning support */
> - if (!umem->context->invalidate_range)
> - put_page(page);
> - umem_odp->page_list[idx] = NULL;
> - umem_odp->dma_list[idx] = 0;
> - umem->npages--;
> - }
> - }
> + ret = hmm_range_dma_unmap(&range, NULL, device,
> + &umem_odp->dma_list[idx], true);
> + if (ret > 0)
> + umem->npages -= ret;
Can hmm_range_dma_unmap fail? If it does, we do we simply leak the DMA
mappings?
> mutex_unlock(&umem_odp->umem_mutex);
> }
Regards,
Haggai
