Commit 30dcc56b authored by Juergen Gross's avatar Juergen Gross
Browse files

xen: assume XENFEAT_gnttab_map_avail_bits being set for pv guests 



XENFEAT_gnttab_map_avail_bits is always set in Xen 4.0 and newer.
Remove coding assuming it might be zero.

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarBoris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20210730071804.4302-4-jgross@suse.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent 2526cff7

drivers/xen/gntdev.c

+2 −34
Original line number Diff line number Diff line
@@ -266,20 +266,13 @@ static int find_grant_ptes(pte_t *pte, unsigned long addr, void *data) 
{

	struct gntdev_grant_map *map = data;

	unsigned int pgnr = (addr - map->vma->vm_start) >> PAGE_SHIFT;

	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte;

	int flags = map->flags | GNTMAP_application_map | GNTMAP_contains_pte |

		    (1 << _GNTMAP_guest_avail0);

	u64 pte_maddr;



	BUG_ON(pgnr >= map->count);

	pte_maddr = arbitrary_virt_to_machine(pte).maddr;



	/*

	 * Set the PTE as special to force get_user_pages_fast() fall

	 * back to the slow path.  If this is not supported as part of

	 * the grant map, it will be done afterwards.

	 */

	if (xen_feature(XENFEAT_gnttab_map_avail_bits))

		flags |= (1 << _GNTMAP_guest_avail0);



	gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, flags,

			  map->grants[pgnr].ref,

			  map->grants[pgnr].domid);
@@ -288,14 +281,6 @@ static int find_grant_ptes(pte_t *pte, unsigned long addr, void *data) 
	return 0;

}



#ifdef CONFIG_X86

static int set_grant_ptes_as_special(pte_t *pte, unsigned long addr, void *data)

{

	set_pte_at(current->mm, addr, pte, pte_mkspecial(*pte));

	return 0;

}

#endif



int gntdev_map_grant_pages(struct gntdev_grant_map *map)

{

	int i, err = 0;
@@ -1055,23 +1040,6 @@ static int gntdev_mmap(struct file *flip, struct vm_area_struct *vma) 
		err = vm_map_pages_zero(vma, map->pages, map->count);

		if (err)

			goto out_put_map;

	} else {

#ifdef CONFIG_X86

		/*

		 * If the PTEs were not made special by the grant map

		 * hypercall, do so here.

		 *

		 * This is racy since the mapping is already visible

		 * to userspace but userspace should be well-behaved

		 * enough to not touch it until the mmap() call

		 * returns.

		 */

		if (!xen_feature(XENFEAT_gnttab_map_avail_bits)) {

			apply_to_page_range(vma->vm_mm, vma->vm_start,

					    vma->vm_end - vma->vm_start,

					    set_grant_ptes_as_special, NULL);

		}

#endif

	}



	return 0;