On 10/21/19 11:32 AM, Jason Gunthorpe wrote:
On Tue, Oct 15, 2019 at 01:48:12PM -0700, Ralph Campbell wrote:
+static bool hmm_range_needs_fault(unsigned long addr, unsigned long end,
+ const struct hmm_vma_walk *hmm_vma_walk)
This has a very similar name to hmm_range_need_fault(), and seems like
it does the same thing?
The two functions are very similar but not identical.
I guess I could resolve the differences and use one function.
+static int hmm_vma_walk_test(unsigned long start, unsigned long end,
+ struct mm_walk *walk)
+{
+ struct hmm_vma_walk *hmm_vma_walk = walk->private;
+ struct hmm_range *range = hmm_vma_walk->range;
+ struct vm_area_struct *vma = walk->vma;
+
+ /* If range is no longer valid, force retry. */
+ if (!range->valid)
+ return -EBUSY;
+
+ /*
+ * Skip vma ranges that don't have struct page backing them or
+ * map I/O devices directly.
+ */
+ if (vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP))
+ return -EFAULT;
+
+ /*
+ * If the vma does not allow read access, then assume that it does not
+ * allow write access either. HMM does not support architectures
+ * that allow write without read.
+ */
+ if (!(vma->vm_flags & VM_READ)) {
+ /*
+ * Check to see if a fault is requested for any page in the
+ * range.
+ */
+ if (hmm_range_needs_fault(start, end, hmm_vma_walk))
+ return -EFAULT;
Is this change to call hmm_range_needs_fault another bug fix?
Jason
Yes. If the HMM_FAULT_SNAPSHOT is specified, there shouldn't be any
error return code. If it is not specified, then the range->pfns[] array,
on input, holds flags indicating which pages the driver wants populated
if the page is not already present. The hmm_range_needs_fault() checks
for this and hmm_vma_walk_test() returns -EFAULT.
I guess I could include this in the change log.
