hmm_range_fault() can be used instead of get_user_pages() for devices
which allow faulting however unlike get_user_pages() it will return an
error when used on a VM_MIXEDMAP range.
To make hmm_range_fault() more closely match get_user_pages() remove
this restriction. This requires dealing with the !ARCH_HAS_PTE_SPECIAL
case in hmm_vma_handle_pte(). Rather than replicating the logic of
vm_normal_page() call it directly and do a check for the zero pfn
similar to what get_user_pages() currently does.
Also add a test to hmm selftest to verify functionality.
Signed-off-by: Alistair Popple <apopple@xxxxxxxxxx>
---
lib/test_hmm.c | 24 +++++++++++++++
mm/hmm.c | 5 +--
tools/testing/selftests/vm/hmm-tests.c | 42 ++++++++++++++++++++++++++
3 files changed, 69 insertions(+), 2 deletions(-)
diff --git a/lib/test_hmm.c b/lib/test_hmm.c
index c259842f6d44..ac794e354069 100644
--- a/lib/test_hmm.c
+++ b/lib/test_hmm.c
@@ -1087,9 +1087,33 @@ static long dmirror_fops_unlocked_ioctl(struct file *filp,
return 0;
}
+static int dmirror_fops_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ unsigned long addr;
+
+ for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
+ struct page *page;
+ int ret;
+
+ page = alloc_page(GFP_KERNEL | __GFP_ZERO);
+ if (!page)
+ return -ENOMEM;
+
+ ret = vm_insert_page(vma, addr, page);
+ if (ret) {
+ __free_page(page);
+ return ret;
+ }
+ put_page(page);
+ }
+
+ return 0;
+}
+
static const struct file_operations dmirror_fops = {
.open = dmirror_fops_open,
.release = dmirror_fops_release,
+ .mmap = dmirror_fops_mmap,
.unlocked_ioctl = dmirror_fops_unlocked_ioctl,
.llseek = default_llseek,
.owner = THIS_MODULE,
diff --git a/mm/hmm.c b/mm/hmm.c
index fad6be2bf072..70fa81a3b629 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -298,7 +298,8 @@ static int hmm_vma_handle_pte(struct mm_walk *walk, unsigned long addr,
* Since each architecture defines a struct page for the zero page, just
* fall through and treat it like a normal page.
*/
- if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
+ if (!vm_normal_page(walk->vma, addr, pte) &&
+ !is_zero_pfn(pte_pfn(pte))) {
if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
pte_unmap(ptep);
return -EFAULT;
@@ -515,7 +516,7 @@ static int hmm_vma_walk_test(unsigned long start, unsigned long end,
struct hmm_range *range = hmm_vma_walk->range;
struct vm_area_struct *vma = walk->vma;
- if (!(vma->vm_flags & (VM_IO | VM_PFNMAP | VM_MIXEDMAP)) &&
+ if (!(vma->vm_flags & (VM_IO | VM_PFNMAP)) &&
vma->vm_flags & VM_READ)
return 0;
diff --git a/tools/testing/selftests/vm/hmm-tests.c b/tools/testing/selftests/vm/hmm-tests.c
index 864f126ffd78..203323967b50 100644
--- a/tools/testing/selftests/vm/hmm-tests.c
+++ b/tools/testing/selftests/vm/hmm-tests.c
@@ -1248,6 +1248,48 @@ TEST_F(hmm, anon_teardown)
}
}
+/*
+ * Test memory snapshot without faulting in pages accessed by the device.
+ */
+TEST_F(hmm, mixedmap)
+{
+ struct hmm_buffer *buffer;
+ unsigned long npages;
+ unsigned long size;
+ unsigned char *m;
+ int ret;
+
+ npages = 1;
+ size = npages << self->page_shift;
+
+ buffer = malloc(sizeof(*buffer));
+ ASSERT_NE(buffer, NULL);
+
+ buffer->fd = -1;
+ buffer->size = size;
+ buffer->mirror = malloc(npages);
+ ASSERT_NE(buffer->mirror, NULL);
+
+
+ /* Reserve a range of addresses. */
+ buffer->ptr = mmap(NULL, size,
+ PROT_READ | PROT_WRITE,
+ MAP_PRIVATE,
+ self->fd, 0);
+ ASSERT_NE(buffer->ptr, MAP_FAILED);
+
+ /* Simulate a device snapshotting CPU pagetables. */
+ ret = hmm_dmirror_cmd(self->fd, HMM_DMIRROR_SNAPSHOT, buffer, npages);
+ ASSERT_EQ(ret, 0);
+ ASSERT_EQ(buffer->cpages, npages);
+
+ /* Check what the device saw. */
+ m = buffer->mirror;
+ ASSERT_EQ(m[0], HMM_DMIRROR_PROT_READ);
+
+ hmm_buffer_free(buffer);
+}
+
/*
* Test memory snapshot without faulting in pages accessed by the device.
*/
--
2.30.2
