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authorDavid Vrabel <david.vrabel@citrix.com>2014-07-11 16:42:34 +0100
committerKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>2014-07-14 15:28:02 -0400
commit162e371712768248a38646eefa71af38b6e0f8ce (patch)
tree899b44d49c7b6cce18e831bb32deb4496d0e016e /drivers/xen
parenta2c5ae65addb122270cf4115c92039c5b8bf15b9 (diff)
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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]
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/grant-table.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 5d4de88fe5b8..eeba7544f0cd 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -1195,18 +1195,20 @@ static int gnttab_expand(unsigned int req_entries)
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 @@ int gnttab_init(void)
}
}
+ 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;