xen/privcmd: Add support for Linux 64KB page granularity

The hypercall interface (as well as the toolstack) is always using 4KB
page granularity. When the toolstack is asking for mapping a series of
guest PFN in a batch, it expects to have the page map contiguously in
its virtual memory.

When Linux is using 64KB page granularity, the privcmd driver will have
to map multiple Xen PFN in a single Linux page.

Note that this solution works on page granularity which is a multiple of
4KB.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/xen/privcmd.c b/drivers/xen/privcmd.c
index b199ad3d4587..df2e6f783318 100644
--- a/drivers/xen/privcmd.c
+++ b/drivers/xen/privcmd.c
@@ -446,7 +446,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
                 return -EINVAL;
         }
 
-        nr_pages = m.num;
+        nr_pages = DIV_ROUND_UP(m.num, XEN_PFN_PER_PAGE);
         if ((m.num <= 0) || (nr_pages > (LONG_MAX >> PAGE_SHIFT)))
                 return -EINVAL;
 
@@ -494,7 +494,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
                         goto out_unlock;
                 }
                 if (xen_feature(XENFEAT_auto_translated_physmap)) {
-                        ret = alloc_empty_pages(vma, m.num);
+                        ret = alloc_empty_pages(vma, nr_pages);
                         if (ret < 0)
                                 goto out_unlock;
                 } else
@@ -518,6 +518,7 @@ static long privcmd_ioctl_mmap_batch(void __user *udata, int version)
         state.global_error  = 0;
         state.version       = version;
 
+        BUILD_BUG_ON(((PAGE_SIZE / sizeof(xen_pfn_t)) % XEN_PFN_PER_PAGE) != 0);
         /* mmap_batch_fn guarantees ret == 0 */
         BUG_ON(traverse_pages_block(m.num, sizeof(xen_pfn_t),
                                     &pagelist, mmap_batch_fn, &state));
@@ -582,12 +583,13 @@ static void privcmd_close(struct vm_area_struct *vma)
 {
         struct page **pages = vma->vm_private_data;
         int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+        int numgfns = (vma->vm_end - vma->vm_start) >> XEN_PAGE_SHIFT;
         int rc;
 
         if (!xen_feature(XENFEAT_auto_translated_physmap) || !numpgs || !pages)
                 return;
 
-        rc = xen_unmap_domain_gfn_range(vma, numpgs, pages);
+        rc = xen_unmap_domain_gfn_range(vma, numgfns, pages);
         if (rc == 0)
                 free_xenballooned_pages(numpgs, pages);
         else