diff options
Diffstat (limited to 'Documentation/vm/hmm.rst')
| -rw-r--r-- | Documentation/vm/hmm.rst | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index 61f073215a8d..945d5fb6d14a 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -217,17 +217,33 @@ respect in order to keep things properly synchronized. The usage pattern is:: range.flags = ...; range.values = ...; range.pfn_shift = ...; + hmm_range_register(&range); + + /* + * Just wait for range to be valid, safe to ignore return value as we + * will use the return value of hmm_range_snapshot() below under the + * mmap_sem to ascertain the validity of the range. + */ + hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC); again: down_read(&mm->mmap_sem); - range.vma = ...; ret = hmm_range_snapshot(&range); if (ret) { up_read(&mm->mmap_sem); + if (ret == -EAGAIN) { + /* + * No need to check hmm_range_wait_until_valid() return value + * on retry we will get proper error with hmm_range_snapshot() + */ + hmm_range_wait_until_valid(&range, TIMEOUT_IN_MSEC); + goto again; + } + hmm_mirror_unregister(&range); return ret; } take_lock(driver->update); - if (!hmm_vma_range_done(vma, &range)) { + if (!range.valid) { release_lock(driver->update); up_read(&mm->mmap_sem); goto again; @@ -235,14 +251,15 @@ respect in order to keep things properly synchronized. The usage pattern is:: // Use pfns array content to update device page table + hmm_mirror_unregister(&range); release_lock(driver->update); up_read(&mm->mmap_sem); return 0; } The driver->update lock is the same lock that the driver takes inside its -update() callback. That lock must be held before hmm_vma_range_done() to avoid -any race with a concurrent CPU page table update. +update() callback. That lock must be held before checking the range.valid +field to avoid any race with a concurrent CPU page table update. HMM implements all this on top of the mmu_notifier API because we wanted a simpler API and also to be able to perform optimizations latter on like doing |