x86/xen: safely map and unmap grant frames when in atomic context
arch_gnttab_map_frames() and arch_gnttab_unmap_frames() are called in
atomic context but were calling alloc_vm_area() which might sleep.
Also, if a driver attempts to allocate a grant ref from an interrupt
and the table needs expanding, then the CPU may already by in lazy MMU
mode and apply_to_page_range() will BUG when it tries to re-enable
lazy MMU mode.
These two functions are only used in PV guests.
Introduce arch_gnttab_init() to allocates the virtual address space in
advance.
Avoid the use of apply_to_page_range() by using saving and using the
array of PTE addresses from the alloc_vm_area() call.
N.B. 'alloc_vm_area' pre-allocates the pagetable so there is no need
to worry about having to do a PGD/PUD/PMD walk (like apply_to_page_range
does) and we can instead do set_pte.
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
----
[v2: Add comment about alloc_vm_area]
[v3: Fix compile error found by 0-day bot]
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 5d4de88..eeba754 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -1195,18 +1195,20 @@
int gnttab_init(void)
{
int i;
+ unsigned long max_nr_grant_frames;
unsigned int max_nr_glist_frames, nr_glist_frames;
unsigned int nr_init_grefs;
int ret;
gnttab_request_version();
+ max_nr_grant_frames = gnttab_max_grant_frames();
nr_grant_frames = 1;
/* Determine the maximum number of frames required for the
* grant reference free list on the current hypervisor.
*/
BUG_ON(grefs_per_grant_frame == 0);
- max_nr_glist_frames = (gnttab_max_grant_frames() *
+ max_nr_glist_frames = (max_nr_grant_frames *
grefs_per_grant_frame / RPP);
gnttab_list = kmalloc(max_nr_glist_frames * sizeof(grant_ref_t *),
@@ -1223,6 +1225,11 @@
}
}
+ ret = arch_gnttab_init(max_nr_grant_frames,
+ nr_status_frames(max_nr_grant_frames));
+ if (ret < 0)
+ goto ini_nomem;
+
if (gnttab_setup() < 0) {
ret = -ENODEV;
goto ini_nomem;