[PATCH v2 12/20] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux
Julien Grall
julien.grall at citrix.com
Thu Jul 9 13:42:24 PDT 2015
For ARM64 guests, Linux is able to support either 64K or 4K page
granularity. Although, the hypercall interface is always based on 4K
page granularity.
With 64K page granuliarty, a single page will be spread over multiple
Xen frame.
When a driver request/free a balloon page, the balloon driver will have
to split the Linux page in 4K chunk before asking Xen to add/remove the
frame from the guest.
Note that this can work on any page granularity assuming it's a multiple
of 4K.
Signed-off-by: Julien Grall <julien.grall at citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky at oracle.com>
Cc: David Vrabel <david.vrabel at citrix.com>
Cc: Wei Liu <wei.liu2 at citrix.com>
---
Changes in v2:
- Use xen_apply_to_page to split a page in 4K chunk
- It's not necessary to have a smaller frame list. Re-use
PAGE_SIZE
- Convert reserve_additional_memory to use XEN_... macro
---
drivers/xen/balloon.c | 147 +++++++++++++++++++++++++++++++++++---------------
1 file changed, 105 insertions(+), 42 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index fd93369..19a72b1 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -230,6 +230,7 @@ static enum bp_state reserve_additional_memory(long credit)
nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
#ifdef CONFIG_XEN_HAVE_PVMMU
+ /* TODO */
/*
* add_memory() will build page tables for the new memory so
* the p2m must contain invalid entries so the correct
@@ -242,8 +243,8 @@ static enum bp_state reserve_additional_memory(long credit)
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
unsigned long pfn, i;
- pfn = PFN_DOWN(hotplug_start_paddr);
- for (i = 0; i < balloon_hotplug; i++) {
+ pfn = XEN_PFN_DOWN(hotplug_start_paddr);
+ for (i = 0; i < (balloon_hotplug * XEN_PFN_PER_PAGE); i++) {
if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
pr_warn("set_phys_to_machine() failed, no memory added\n");
return BP_ECANCELED;
@@ -323,10 +324,72 @@ static enum bp_state reserve_additional_memory(long credit)
}
#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
+static int set_frame(struct page *page, unsigned long pfn, void *data)
+{
+ unsigned long *index = data;
+
+ frame_list[(*index)++] = pfn;
+
+ return 0;
+}
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+static int pvmmu_update_mapping(struct page *page, unsigned long pfn,
+ void *data)
+{
+ unsigned long *index = data;
+ xen_pfn_t frame = frame_list[*index];
+
+ set_phys_to_machine(pfn, frame);
+ /* Link back into the page tables if not highmem. */
+ if (!PageHighMem(page)) {
+ int ret;
+ ret = HYPERVISOR_update_va_mapping(
+ (unsigned long)__va(pfn << XEN_PAGE_SHIFT),
+ mfn_pte(frame, PAGE_KERNEL),
+ 0);
+ BUG_ON(ret);
+ }
+
+ (*index)++;
+
+ return 0;
+}
+#endif
+
+static int balloon_remove_mapping(struct page *page, unsigned long pfn,
+ void *data)
+{
+ unsigned long *index = data;
+
+ /* We expect the frame_list to contain the same pfn */
+ BUG_ON(pfn != frame_list[*index]);
+
+ frame_list[*index] = pfn_to_mfn(pfn);
+
+#ifdef CONFIG_XEN_HAVE_PVMMU
+ if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ if (!PageHighMem(page)) {
+ int ret;
+
+ ret = HYPERVISOR_update_va_mapping(
+ (unsigned long)__va(pfn << XEN_PAGE_SHIFT),
+ __pte_ma(0), 0);
+ BUG_ON(ret);
+ }
+ __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+ }
+#endif
+
+ (*index)++;
+
+ return 0;
+}
+
static enum bp_state increase_reservation(unsigned long nr_pages)
{
int rc;
- unsigned long pfn, i;
+ unsigned long i, frame_idx;
struct page *page;
struct xen_memory_reservation reservation = {
.address_bits = 0,
@@ -343,44 +406,43 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
}
#endif
- if (nr_pages > ARRAY_SIZE(frame_list))
- nr_pages = ARRAY_SIZE(frame_list);
+ if (nr_pages > (ARRAY_SIZE(frame_list) / XEN_PFN_PER_PAGE))
+ nr_pages = ARRAY_SIZE(frame_list) / XEN_PFN_PER_PAGE;
+ frame_idx = 0;
page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
for (i = 0; i < nr_pages; i++) {
if (!page) {
nr_pages = i;
break;
}
- frame_list[i] = page_to_pfn(page);
+
+ rc = xen_apply_to_page(page, set_frame, &frame_idx);
+
page = balloon_next_page(page);
}
set_xen_guest_handle(reservation.extent_start, frame_list);
- reservation.nr_extents = nr_pages;
+ reservation.nr_extents = nr_pages * XEN_PFN_PER_PAGE;
rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
if (rc <= 0)
return BP_EAGAIN;
- for (i = 0; i < rc; i++) {
+ /* rc is equal to the number of Xen page populated */
+ nr_pages = rc / XEN_PFN_PER_PAGE;
+
+ for (i = 0; i < nr_pages; i++) {
page = balloon_retrieve(false);
BUG_ON(page == NULL);
- pfn = page_to_pfn(page);
-
#ifdef CONFIG_XEN_HAVE_PVMMU
+ frame_idx = 0;
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- set_phys_to_machine(pfn, frame_list[i]);
-
- /* Link back into the page tables if not highmem. */
- if (!PageHighMem(page)) {
- int ret;
- ret = HYPERVISOR_update_va_mapping(
- (unsigned long)__va(pfn << PAGE_SHIFT),
- mfn_pte(frame_list[i], PAGE_KERNEL),
- 0);
- BUG_ON(ret);
- }
+ int ret;
+
+ ret = xen_apply_to_page(page, pvmmu_update_mapping,
+ &frame_idx);
+ BUG_ON(ret);
}
#endif
@@ -388,7 +450,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
__free_reserved_page(page);
}
- balloon_stats.current_pages += rc;
+ balloon_stats.current_pages += nr_pages;
return BP_DONE;
}
@@ -396,7 +458,7 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
{
enum bp_state state = BP_DONE;
- unsigned long pfn, i;
+ unsigned long pfn, i, frame_idx, nr_frames;
struct page *page;
int ret;
struct xen_memory_reservation reservation = {
@@ -414,9 +476,10 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
}
#endif
- if (nr_pages > ARRAY_SIZE(frame_list))
- nr_pages = ARRAY_SIZE(frame_list);
+ if (nr_pages > (ARRAY_SIZE(frame_list) / XEN_PFN_PER_PAGE))
+ nr_pages = ARRAY_SIZE(frame_list) / XEN_PFN_PER_PAGE;
+ frame_idx = 0;
for (i = 0; i < nr_pages; i++) {
page = alloc_page(gfp);
if (page == NULL) {
@@ -426,9 +489,12 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
}
scrub_page(page);
- frame_list[i] = page_to_pfn(page);
+ ret = xen_apply_to_page(page, set_frame, &frame_idx);
+ BUG_ON(ret);
}
+ nr_frames = nr_pages * XEN_PFN_PER_PAGE;
+
/*
* Ensure that ballooned highmem pages don't have kmaps.
*
@@ -439,22 +505,19 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
kmap_flush_unused();
/* Update direct mapping, invalidate P2M, and add to balloon. */
+ frame_idx = 0;
for (i = 0; i < nr_pages; i++) {
- pfn = frame_list[i];
- frame_list[i] = pfn_to_mfn(pfn);
- page = pfn_to_page(pfn);
+ /*
+ * The Xen PFN for a given Linux Page are contiguous in
+ * frame_list
+ */
+ pfn = frame_list[frame_idx];
+ page = xen_pfn_to_page(pfn);
-#ifdef CONFIG_XEN_HAVE_PVMMU
- if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- if (!PageHighMem(page)) {
- ret = HYPERVISOR_update_va_mapping(
- (unsigned long)__va(pfn << PAGE_SHIFT),
- __pte_ma(0), 0);
- BUG_ON(ret);
- }
- __set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
- }
-#endif
+
+ ret = xen_apply_to_page(page, balloon_remove_mapping,
+ &frame_idx);
+ BUG_ON(ret);
balloon_append(page);
}
@@ -462,9 +525,9 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
flush_tlb_all();
set_xen_guest_handle(reservation.extent_start, frame_list);
- reservation.nr_extents = nr_pages;
+ reservation.nr_extents = nr_frames;
ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
- BUG_ON(ret != nr_pages);
+ BUG_ON(ret != nr_frames);
balloon_stats.current_pages -= nr_pages;
--
2.1.4
More information about the linux-arm-kernel
mailing list