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/arch/arm/xen/grant-table.c b/arch/arm/xen/grant-table.c
index 859a9bb..91cf08b 100644
--- a/arch/arm/xen/grant-table.c
+++ b/arch/arm/xen/grant-table.c
@@ -51,3 +51,8 @@
{
return -ENOSYS;
}
+
+int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
+{
+ return 0;
+}
diff --git a/arch/x86/xen/grant-table.c b/arch/x86/xen/grant-table.c
index c985835..ebfa9b2 100644
--- a/arch/x86/xen/grant-table.c
+++ b/arch/x86/xen/grant-table.c
@@ -36,99 +36,133 @@
#include <linux/sched.h>
#include <linux/mm.h>
+#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <xen/interface/xen.h>
#include <xen/page.h>
#include <xen/grant_table.h>
+#include <xen/xen.h>
#include <asm/pgtable.h>
-static int map_pte_fn(pte_t *pte, struct page *pmd_page,
- unsigned long addr, void *data)
-{
- unsigned long **frames = (unsigned long **)data;
-
- set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
- (*frames)++;
- return 0;
-}
-
-/*
- * This function is used to map shared frames to store grant status. It is
- * different from map_pte_fn above, the frames type here is uint64_t.
- */
-static int map_pte_fn_status(pte_t *pte, struct page *pmd_page,
- unsigned long addr, void *data)
-{
- uint64_t **frames = (uint64_t **)data;
-
- set_pte_at(&init_mm, addr, pte, mfn_pte((*frames)[0], PAGE_KERNEL));
- (*frames)++;
- return 0;
-}
-
-static int unmap_pte_fn(pte_t *pte, struct page *pmd_page,
- unsigned long addr, void *data)
-{
-
- set_pte_at(&init_mm, addr, pte, __pte(0));
- return 0;
-}
+static struct gnttab_vm_area {
+ struct vm_struct *area;
+ pte_t **ptes;
+} gnttab_shared_vm_area, gnttab_status_vm_area;
int arch_gnttab_map_shared(unsigned long *frames, unsigned long nr_gframes,
unsigned long max_nr_gframes,
void **__shared)
{
- int rc;
void *shared = *__shared;
+ unsigned long addr;
+ unsigned long i;
- if (shared == NULL) {
- struct vm_struct *area =
- alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);
- BUG_ON(area == NULL);
- shared = area->addr;
- *__shared = shared;
+ if (shared == NULL)
+ *__shared = shared = gnttab_shared_vm_area.area->addr;
+
+ addr = (unsigned long)shared;
+
+ for (i = 0; i < nr_gframes; i++) {
+ set_pte_at(&init_mm, addr, gnttab_shared_vm_area.ptes[i],
+ mfn_pte(frames[i], PAGE_KERNEL));
+ addr += PAGE_SIZE;
}
- rc = apply_to_page_range(&init_mm, (unsigned long)shared,
- PAGE_SIZE * nr_gframes,
- map_pte_fn, &frames);
- return rc;
+ return 0;
}
int arch_gnttab_map_status(uint64_t *frames, unsigned long nr_gframes,
unsigned long max_nr_gframes,
grant_status_t **__shared)
{
- int rc;
grant_status_t *shared = *__shared;
+ unsigned long addr;
+ unsigned long i;
- if (shared == NULL) {
- /* No need to pass in PTE as we are going to do it
- * in apply_to_page_range anyhow. */
- struct vm_struct *area =
- alloc_vm_area(PAGE_SIZE * max_nr_gframes, NULL);
- BUG_ON(area == NULL);
- shared = area->addr;
- *__shared = shared;
+ if (shared == NULL)
+ *__shared = shared = gnttab_status_vm_area.area->addr;
+
+ addr = (unsigned long)shared;
+
+ for (i = 0; i < nr_gframes; i++) {
+ set_pte_at(&init_mm, addr, gnttab_status_vm_area.ptes[i],
+ mfn_pte(frames[i], PAGE_KERNEL));
+ addr += PAGE_SIZE;
}
- rc = apply_to_page_range(&init_mm, (unsigned long)shared,
- PAGE_SIZE * nr_gframes,
- map_pte_fn_status, &frames);
- return rc;
+ return 0;
}
void arch_gnttab_unmap(void *shared, unsigned long nr_gframes)
{
- apply_to_page_range(&init_mm, (unsigned long)shared,
- PAGE_SIZE * nr_gframes, unmap_pte_fn, NULL);
+ pte_t **ptes;
+ unsigned long addr;
+ unsigned long i;
+
+ if (shared == gnttab_status_vm_area.area->addr)
+ ptes = gnttab_status_vm_area.ptes;
+ else
+ ptes = gnttab_shared_vm_area.ptes;
+
+ addr = (unsigned long)shared;
+
+ for (i = 0; i < nr_gframes; i++) {
+ set_pte_at(&init_mm, addr, ptes[i], __pte(0));
+ addr += PAGE_SIZE;
+ }
}
+
+static int arch_gnttab_valloc(struct gnttab_vm_area *area, unsigned nr_frames)
+{
+ area->ptes = kmalloc(sizeof(pte_t *) * nr_frames, GFP_KERNEL);
+ if (area->ptes == NULL)
+ return -ENOMEM;
+
+ area->area = alloc_vm_area(PAGE_SIZE * nr_frames, area->ptes);
+ if (area->area == NULL) {
+ kfree(area->ptes);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void arch_gnttab_vfree(struct gnttab_vm_area *area)
+{
+ free_vm_area(area->area);
+ kfree(area->ptes);
+}
+
+int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status)
+{
+ int ret;
+
+ if (!xen_pv_domain())
+ return 0;
+
+ ret = arch_gnttab_valloc(&gnttab_shared_vm_area, nr_shared);
+ if (ret < 0)
+ return ret;
+
+ /*
+ * Always allocate the space for the status frames in case
+ * we're migrated to a host with V2 support.
+ */
+ ret = arch_gnttab_valloc(&gnttab_status_vm_area, nr_status);
+ if (ret < 0)
+ goto err;
+
+ return 0;
+ err:
+ arch_gnttab_vfree(&gnttab_shared_vm_area);
+ return -ENOMEM;
+}
+
#ifdef CONFIG_XEN_PVH
#include <xen/balloon.h>
#include <xen/events.h>
-#include <xen/xen.h>
#include <linux/slab.h>
static int __init xlated_setup_gnttab_pages(void)
{
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;
diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
index a5af2a2..5c1aba1 100644
--- a/include/xen/grant_table.h
+++ b/include/xen/grant_table.h
@@ -170,6 +170,7 @@
unmap->dev_bus_addr = 0;
}
+int arch_gnttab_init(unsigned long nr_shared, unsigned long nr_status);
int arch_gnttab_map_shared(xen_pfn_t *frames, unsigned long nr_gframes,
unsigned long max_nr_gframes,
void **__shared);