Xen: Fix retry calls into PRIVCMD_MMAPBATCH*.
When a foreign mapper attempts to map guest frames that are paged out,
the mapper receives an ENOENT response and will have to try again
while a helper process pages the target frame back in.
Gating checks on PRIVCMD_MMAPBATCH* ioctl args were preventing retries
of mapping calls.
Permit subsequent calls to update a sub-range of the VMA, iff nothing
is yet mapped in that range.
Since it is now valid to call PRIVCMD_MMAPBATCH* multiple times, only
set vma->vm_private_data if the parameters are valid and (if
necessary) the pages for the auto_translated_physmap case have been
allocated. This prevents subsequent calls from incorrectly entering
the 'retry' path when there are no pages allocated etc.
Signed-off-by: Andres Lagar-Cavilla <andres@lagarcavilla.org>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index f8e5dd70..8e74590 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -43,9 +43,10 @@
#define PRIV_VMA_LOCKED ((void *)1)
-#ifndef HAVE_ARCH_PRIVCMD_MMAP
-static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma);
-#endif
+static int privcmd_vma_range_is_mapped(
+ struct vm_area_struct *vma,
+ unsigned long addr,
+ unsigned long nr_pages);
static long privcmd_ioctl_hypercall(void __user *udata)
{
@@ -225,9 +226,9 @@
vma = find_vma(mm, msg->va);
rc = -EINVAL;
- if (!vma || (msg->va != vma->vm_start) ||
- !privcmd_enforce_singleshot_mapping(vma))
+ if (!vma || (msg->va != vma->vm_start) || vma->vm_private_data)
goto out_up;
+ vma->vm_private_data = PRIV_VMA_LOCKED;
}
state.va = vma->vm_start;
@@ -358,7 +359,7 @@
kfree(pages);
return -ENOMEM;
}
- BUG_ON(vma->vm_private_data != PRIV_VMA_LOCKED);
+ BUG_ON(vma->vm_private_data != NULL);
vma->vm_private_data = pages;
return 0;
@@ -421,19 +422,43 @@
vma = find_vma(mm, m.addr);
if (!vma ||
- vma->vm_ops != &privcmd_vm_ops ||
- (m.addr != vma->vm_start) ||
- ((m.addr + (nr_pages << PAGE_SHIFT)) != vma->vm_end) ||
- !privcmd_enforce_singleshot_mapping(vma)) {
- up_write(&mm->mmap_sem);
+ vma->vm_ops != &privcmd_vm_ops) {
ret = -EINVAL;
- goto out;
+ goto out_unlock;
}
- if (xen_feature(XENFEAT_auto_translated_physmap)) {
- ret = alloc_empty_pages(vma, m.num);
- if (ret < 0) {
- up_write(&mm->mmap_sem);
- goto out;
+
+ /*
+ * Caller must either:
+ *
+ * Map the whole VMA range, which will also allocate all the
+ * pages required for the auto_translated_physmap case.
+ *
+ * Or
+ *
+ * Map unmapped holes left from a previous map attempt (e.g.,
+ * because those foreign frames were previously paged out).
+ */
+ if (vma->vm_private_data == NULL) {
+ if (m.addr != vma->vm_start ||
+ m.addr + (nr_pages << PAGE_SHIFT) != vma->vm_end) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ if (xen_feature(XENFEAT_auto_translated_physmap)) {
+ ret = alloc_empty_pages(vma, m.num);
+ if (ret < 0)
+ goto out_unlock;
+ } else
+ vma->vm_private_data = PRIV_VMA_LOCKED;
+ } else {
+ if (m.addr < vma->vm_start ||
+ m.addr + (nr_pages << PAGE_SHIFT) > vma->vm_end) {
+ ret = -EINVAL;
+ goto out_unlock;
+ }
+ if (privcmd_vma_range_is_mapped(vma, m.addr, nr_pages)) {
+ ret = -EINVAL;
+ goto out_unlock;
}
}
@@ -466,8 +491,11 @@
out:
free_page_list(&pagelist);
-
return ret;
+
+out_unlock:
+ up_write(&mm->mmap_sem);
+ goto out;
}
static long privcmd_ioctl(struct file *file,
@@ -540,9 +568,24 @@
return 0;
}
-static int privcmd_enforce_singleshot_mapping(struct vm_area_struct *vma)
+/*
+ * For MMAPBATCH*. This allows asserting the singleshot mapping
+ * on a per pfn/pte basis. Mapping calls that fail with ENOENT
+ * can be then retried until success.
+ */
+static int is_mapped_fn(pte_t *pte, struct page *pmd_page,
+ unsigned long addr, void *data)
{
- return !cmpxchg(&vma->vm_private_data, NULL, PRIV_VMA_LOCKED);
+ return pte_none(*pte) ? 0 : -EBUSY;
+}
+
+static int privcmd_vma_range_is_mapped(
+ struct vm_area_struct *vma,
+ unsigned long addr,
+ unsigned long nr_pages)
+{
+ return apply_to_page_range(vma->vm_mm, addr, nr_pages << PAGE_SHIFT,
+ is_mapped_fn, NULL) != 0;
}
const struct file_operations xen_privcmd_fops = {