[RFC 15/23] xen/balloon: Don't rely on the page granularity is the same for Xen and Linux
Julien Grall
julien.grall at citrix.com
Thu May 14 10:00:55 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>
---
TODO/LIMITATIONS:
- When CONFIG_XEN_HAVE_PMMU only 4K page granularity is supported
- It may be possible to extend the concept for ballooning 2M/1G
page.
---
drivers/xen/balloon.c | 93 +++++++++++++++++++++++++++++++++------------------
1 file changed, 60 insertions(+), 33 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index fd93369..f0d8666 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -91,7 +91,7 @@ struct balloon_stats balloon_stats;
EXPORT_SYMBOL_GPL(balloon_stats);
/* We increase/decrease in batches which fit in a page */
-static xen_pfn_t frame_list[PAGE_SIZE / sizeof(unsigned long)];
+static xen_pfn_t frame_list[XEN_PAGE_SIZE / sizeof(unsigned long)];
/* List of ballooned pages, threaded through the mem_map array. */
@@ -326,7 +326,7 @@ static enum bp_state reserve_additional_memory(long credit)
static enum bp_state increase_reservation(unsigned long nr_pages)
{
int rc;
- unsigned long pfn, i;
+ unsigned long pfn, i, nr_frames;
struct page *page;
struct xen_memory_reservation reservation = {
.address_bits = 0,
@@ -343,30 +343,43 @@ 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;
+
+ nr_frames = nr_pages * XEN_PFN_PER_PAGE;
+
+ pfn = 0; /* make gcc happy */
page = list_first_entry_or_null(&ballooned_pages, struct page, lru);
- for (i = 0; i < nr_pages; i++) {
- if (!page) {
- nr_pages = i;
- break;
+ for (i = 0; i < nr_frames; i++) {
+ if (!(i % XEN_PFN_PER_PAGE)) {
+ if (!page) {
+ nr_frames = i;
+ break;
+ }
+ pfn = xen_page_to_pfn(page);
+ page = balloon_next_page(page);
}
- frame_list[i] = page_to_pfn(page);
- page = balloon_next_page(page);
+ frame_list[i] = pfn++;
}
set_xen_guest_handle(reservation.extent_start, frame_list);
- reservation.nr_extents = nr_pages;
+ reservation.nr_extents = nr_frames;
rc = HYPERVISOR_memory_op(XENMEM_populate_physmap, &reservation);
if (rc <= 0)
return BP_EAGAIN;
for (i = 0; i < rc; i++) {
- page = balloon_retrieve(false);
- BUG_ON(page == NULL);
- pfn = page_to_pfn(page);
+ /* TODO: Make this code cleaner to make CONFIG_XEN_HAVE_PVMMU
+ * with 64K Pages
+ */
+ if (!(i % XEN_PFN_PER_PAGE)) {
+ page = balloon_retrieve(false);
+ BUG_ON(page == NULL);
+
+ pfn = page_to_pfn(page);
+ }
#ifdef CONFIG_XEN_HAVE_PVMMU
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
@@ -385,7 +398,8 @@ static enum bp_state increase_reservation(unsigned long nr_pages)
#endif
/* Relinquish the page back to the allocator. */
- __free_reserved_page(page);
+ if (!(i % XEN_PFN_PER_PAGE))
+ __free_reserved_page(page);
}
balloon_stats.current_pages += rc;
@@ -396,7 +410,7 @@ 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, nr_frames;
struct page *page;
int ret;
struct xen_memory_reservation reservation = {
@@ -414,19 +428,27 @@ 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;
- for (i = 0; i < nr_pages; i++) {
- page = alloc_page(gfp);
- if (page == NULL) {
- nr_pages = i;
- state = BP_EAGAIN;
- break;
+ nr_frames = nr_pages * XEN_PFN_PER_PAGE;
+
+ pfn = 0; /* Make GCC happy */
+
+ for (i = 0; i < nr_frames; i++) {
+
+ if (!(i % XEN_PFN_PER_PAGE)) {
+ page = alloc_page(gfp);
+ if (page == NULL) {
+ nr_frames = i;
+ state = BP_EAGAIN;
+ break;
+ }
+ scrub_page(page);
+ pfn = xen_page_to_pfn(page);
}
- scrub_page(page);
- frame_list[i] = page_to_pfn(page);
+ frame_list[i] = pfn++;
}
/*
@@ -439,16 +461,20 @@ 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. */
- for (i = 0; i < nr_pages; i++) {
+ for (i = 0; i < nr_frames; i++) {
pfn = frame_list[i];
frame_list[i] = pfn_to_mfn(pfn);
- page = pfn_to_page(pfn);
+ page = xen_pfn_to_page(pfn);
+
+ /* TODO: Make this code cleaner to make CONFIG_XEN_HAVE_PVMMU
+ * work with 64K pages
+ */
#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),
+ (unsigned long)__va(pfn << XEN_PAGE_SHIFT),
__pte_ma(0), 0);
BUG_ON(ret);
}
@@ -456,17 +482,18 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
}
#endif
- balloon_append(page);
+ if (!(i % XEN_PFN_PER_PAGE))
+ balloon_append(page);
}
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;
+ balloon_stats.current_pages -= nr_frames * XEN_PFN_PER_PAGE;
return state;
}
--
2.1.4
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