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 granularity, a single page will be spread over multiple
Xen frame.
To avoid splitting the page into 4K frame, take advantage of the
extent_order field to directly allocate/free chunk of the Linux page
size.
Note that PVMMU is only used for PV guest (which is x86) and the page
granularity is always 4KB. Some BUILD_BUG_ON has been added to ensure
that because the code has not been modified.
Signed-off-by: Julien Grall <julien.gr...@citrix.com>
---
Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
Cc: Boris Ostrovsky <boris.ostrov...@oracle.com>
Cc: David Vrabel <david.vra...@citrix.com>
Cc: Wei Liu <wei.l...@citrix.com>
Changes in v3:
- Fix errors reported by checkpatch.pl
- s/mfn/gfn/ based on the new naming
- Rather than splitting the page into 4KB chunk, use the
extent_order field to allocate directly a Linux page size. This
is avoid lots of code for no benefits.
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 | 47 ++++++++++++++++++++++++++++++++++++-----------
1 file changed, 36 insertions(+), 11 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 9734649..c8739c8 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -70,6 +70,9 @@
#include <xen/features.h>
#include <xen/page.h>
+/* Use one extent per PAGE_SIZE to avoid break down into multiple frame */
+#define EXTENT_ORDER (fls(XEN_PFN_PER_PAGE) - 1)
+
/*
* balloon_process() state:
*
@@ -230,6 +233,11 @@ static enum bp_state reserve_additional_memory(long credit)
nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
#ifdef CONFIG_XEN_HAVE_PVMMU
+ /* We don't support PV MMU when Linux and Xen is using
+ * different page granularity.
+ */
+ BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
/*
* add_memory() will build page tables for the new memory so
* the p2m must contain invalid entries so the correct
@@ -326,11 +334,11 @@ 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 i;
struct page *page;
struct xen_memory_reservation reservation = {
.address_bits = 0,
- .extent_order = 0,
+ .extent_order = EXTENT_ORDER,
.domid = DOMID_SELF
};
@@ -352,7 +360,11 @@ static enum bp_state increase_reservation(unsigned long
nr_pages)
nr_pages = i;
break;
}
- frame_list[i] = page_to_pfn(page);
+
+ /* XENMEM_populate_physmap requires a PFN based on Xen
+ * granularity.
+ */
+ frame_list[i] = xen_page_to_pfn(page);
page = balloon_next_page(page);
}
@@ -366,10 +378,15 @@ static enum bp_state increase_reservation(unsigned long
nr_pages)
page = balloon_retrieve(false);
BUG_ON(page == NULL);
- pfn = page_to_pfn(page);
-
#ifdef CONFIG_XEN_HAVE_PVMMU
+ /* We don't support PV MMU when Linux and Xen is using
+ * different page granularity.
+ */
+ BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ unsigned long pfn = page_to_pfn(page);
+
set_phys_to_machine(pfn, frame_list[i]);
/* Link back into the page tables if not highmem. */
@@ -396,14 +413,15 @@ 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 i;
struct page *page;
int ret;
struct xen_memory_reservation reservation = {
.address_bits = 0,
- .extent_order = 0,
+ .extent_order = EXTENT_ORDER,
.domid = DOMID_SELF
};
+ static struct page *pages[ARRAY_SIZE(frame_list)];
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
if (balloon_stats.hotplug_pages) {
@@ -426,7 +444,9 @@ static enum bp_state decrease_reservation(unsigned long
nr_pages, gfp_t gfp)
}
scrub_page(page);
- frame_list[i] = page_to_pfn(page);
+ /* XENMEM_decrease_reservation requires a GFN */
+ frame_list[i] = xen_page_to_gfn(page);
+ pages[i] = page;
}
/*
@@ -440,12 +460,17 @@ static enum bp_state decrease_reservation(unsigned long
nr_pages, gfp_t gfp)
/* Update direct mapping, invalidate P2M, and add to balloon. */
for (i = 0; i < nr_pages; i++) {
- pfn = frame_list[i];
- frame_list[i] = pfn_to_gfn(pfn);
- page = pfn_to_page(pfn);
+ page = pages[i];
#ifdef CONFIG_XEN_HAVE_PVMMU
+ /* We don't support PV MMU when Linux and Xen is using
+ * different page granularity.
+ */
+ BUILD_BUG_ON(XEN_PAGE_SIZE != PAGE_SIZE);
+
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ unsigned long pfn = page_to_pfn(page);
+
if (!PageHighMem(page)) {
ret = HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn <<
PAGE_SHIFT),
--
2.1.4
--
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