diff options
| -rw-r--r-- | Documentation/vm/hmm.rst | 8 | ||||
| -rw-r--r-- | include/linux/hmm.h | 13 | ||||
| -rw-r--r-- | mm/hmm.c | 91 |
3 files changed, 52 insertions, 60 deletions
diff --git a/Documentation/vm/hmm.rst b/Documentation/vm/hmm.rst index d9b27bdadd1b..61f073215a8d 100644 --- a/Documentation/vm/hmm.rst +++ b/Documentation/vm/hmm.rst @@ -190,13 +190,7 @@ When the device driver wants to populate a range of virtual addresses, it can use either:: long hmm_range_snapshot(struct hmm_range *range); - int hmm_vma_fault(struct vm_area_struct *vma, - struct hmm_range *range, - unsigned long start, - unsigned long end, - hmm_pfn_t *pfns, - bool write, - bool block); + long hmm_range_fault(struct hmm_range *range, bool block); The first one (hmm_range_snapshot()) will only fetch present CPU page table entries and will not trigger a page fault on missing or non-present entries. diff --git a/include/linux/hmm.h b/include/linux/hmm.h index 32206b0b1bfd..e9afd23c2eac 100644 --- a/include/linux/hmm.h +++ b/include/linux/hmm.h @@ -391,7 +391,18 @@ bool hmm_vma_range_done(struct hmm_range *range); * * See the function description in mm/hmm.c for further documentation. */ -int hmm_vma_fault(struct hmm_range *range, bool block); +long hmm_range_fault(struct hmm_range *range, bool block); + +/* This is a temporary helper to avoid merge conflict between trees. */ +static inline int hmm_vma_fault(struct hmm_range *range, bool block) +{ + long ret = hmm_range_fault(range, block); + if (ret == -EBUSY) + ret = -EAGAIN; + else if (ret == -EAGAIN) + ret = -EBUSY; + return ret < 0 ? ret : 0; +} /* Below are for HMM internal use only! Not to be used by device driver! */ void hmm_mm_destroy(struct mm_struct *mm); @@ -340,13 +340,13 @@ static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr, flags |= write_fault ? FAULT_FLAG_WRITE : 0; ret = handle_mm_fault(vma, addr, flags); if (ret & VM_FAULT_RETRY) - return -EBUSY; + return -EAGAIN; if (ret & VM_FAULT_ERROR) { *pfn = range->values[HMM_PFN_ERROR]; return -EFAULT; } - return -EAGAIN; + return -EBUSY; } static int hmm_pfns_bad(unsigned long addr, @@ -372,7 +372,7 @@ static int hmm_pfns_bad(unsigned long addr, * @fault: should we fault or not ? * @write_fault: write fault ? * @walk: mm_walk structure - * Returns: 0 on success, -EAGAIN after page fault, or page fault error + * Returns: 0 on success, -EBUSY after page fault, or page fault error * * This function will be called whenever pmd_none() or pte_none() returns true, * or whenever there is no page directory covering the virtual address range. @@ -395,12 +395,12 @@ static int hmm_vma_walk_hole_(unsigned long addr, unsigned long end, ret = hmm_vma_do_fault(walk, addr, write_fault, &pfns[i]); - if (ret != -EAGAIN) + if (ret != -EBUSY) return ret; } } - return (fault || write_fault) ? -EAGAIN : 0; + return (fault || write_fault) ? -EBUSY : 0; } static inline void hmm_pte_need_fault(const struct hmm_vma_walk *hmm_vma_walk, @@ -531,11 +531,11 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, uint64_t orig_pfn = *pfn; *pfn = range->values[HMM_PFN_NONE]; - cpu_flags = pte_to_hmm_pfn_flags(range, pte); - hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, - &fault, &write_fault); + fault = write_fault = false; if (pte_none(pte)) { + hmm_pte_need_fault(hmm_vma_walk, orig_pfn, 0, + &fault, &write_fault); if (fault || write_fault) goto fault; return 0; @@ -574,7 +574,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, hmm_vma_walk->last = addr; migration_entry_wait(vma->vm_mm, pmdp, addr); - return -EAGAIN; + return -EBUSY; } return 0; } @@ -582,6 +582,10 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr, /* Report error for everything else */ *pfn = range->values[HMM_PFN_ERROR]; return -EFAULT; + } else { + cpu_flags = pte_to_hmm_pfn_flags(range, pte); + hmm_pte_need_fault(hmm_vma_walk, orig_pfn, cpu_flags, + &fault, &write_fault); } if (fault || write_fault) @@ -632,7 +636,7 @@ again: if (fault || write_fault) { hmm_vma_walk->last = addr; pmd_migration_entry_wait(vma->vm_mm, pmdp); - return -EAGAIN; + return -EBUSY; } return 0; } else if (!pmd_present(pmd)) @@ -860,53 +864,34 @@ bool hmm_vma_range_done(struct hmm_range *range) EXPORT_SYMBOL(hmm_vma_range_done); /* - * hmm_vma_fault() - try to fault some address in a virtual address range + * hmm_range_fault() - try to fault some address in a virtual address range * @range: range being faulted * @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem) - * Returns: 0 success, error otherwise (-EAGAIN means mmap_sem have been drop) + * Returns: number of valid pages in range->pfns[] (from range start + * address). This may be zero. If the return value is negative, + * then one of the following values may be returned: + * + * -EINVAL invalid arguments or mm or virtual address are in an + * invalid vma (ie either hugetlbfs or device file vma). + * -ENOMEM: Out of memory. + * -EPERM: Invalid permission (for instance asking for write and + * range is read only). + * -EAGAIN: If you need to retry and mmap_sem was drop. This can only + * happens if block argument is false. + * -EBUSY: If the the range is being invalidated and you should wait + * for invalidation to finish. + * -EFAULT: Invalid (ie either no valid vma or it is illegal to access + * that range), number of valid pages in range->pfns[] (from + * range start address). * * This is similar to a regular CPU page fault except that it will not trigger - * any memory migration if the memory being faulted is not accessible by CPUs. + * any memory migration if the memory being faulted is not accessible by CPUs + * and caller does not ask for migration. * * On error, for one virtual address in the range, the function will mark the * corresponding HMM pfn entry with an error flag. - * - * Expected use pattern: - * retry: - * down_read(&mm->mmap_sem); - * // Find vma and address device wants to fault, initialize hmm_pfn_t - * // array accordingly - * ret = hmm_vma_fault(range, write, block); - * switch (ret) { - * case -EAGAIN: - * hmm_vma_range_done(range); - * // You might want to rate limit or yield to play nicely, you may - * // also commit any valid pfn in the array assuming that you are - * // getting true from hmm_vma_range_monitor_end() - * goto retry; - * case 0: - * break; - * case -ENOMEM: - * case -EINVAL: - * case -EPERM: - * default: - * // Handle error ! - * up_read(&mm->mmap_sem) - * return; - * } - * // Take device driver lock that serialize device page table update - * driver_lock_device_page_table_update(); - * hmm_vma_range_done(range); - * // Commit pfns we got from hmm_vma_fault() - * driver_unlock_device_page_table_update(); - * up_read(&mm->mmap_sem) - * - * YOU MUST CALL hmm_vma_range_done() AFTER THIS FUNCTION RETURN SUCCESS (0) - * BEFORE FREEING THE range struct OR YOU WILL HAVE SERIOUS MEMORY CORRUPTION ! - * - * YOU HAVE BEEN WARNED ! */ -int hmm_vma_fault(struct hmm_range *range, bool block) +long hmm_range_fault(struct hmm_range *range, bool block) { struct vm_area_struct *vma = range->vma; unsigned long start = range->start; @@ -978,7 +963,8 @@ int hmm_vma_fault(struct hmm_range *range, bool block) do { ret = walk_page_range(start, range->end, &mm_walk); start = hmm_vma_walk.last; - } while (ret == -EAGAIN); + /* Keep trying while the range is valid. */ + } while (ret == -EBUSY && range->valid); if (ret) { unsigned long i; @@ -988,6 +974,7 @@ int hmm_vma_fault(struct hmm_range *range, bool block) range->end); hmm_vma_range_done(range); hmm_put(hmm); + return ret; } else { /* * Transfer hmm reference to the range struct it will be drop @@ -997,9 +984,9 @@ int hmm_vma_fault(struct hmm_range *range, bool block) range->hmm = hmm; } - return ret; + return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT; } -EXPORT_SYMBOL(hmm_vma_fault); +EXPORT_SYMBOL(hmm_range_fault); #endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */ |