xen: add configurable max domain size
Add a config option to set the max size of a Xen domain. This is used
to scale the size of the physical-to-machine array; it ends up using
around 1 page/GByte, so there's no reason to be very restrictive.
For a 32-bit guest, the default value of 8GB is probably sufficient;
there's not much point in giving a 32-bit machine much more memory
than that.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index c3b27de..644232a 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -56,19 +56,13 @@
#include "multicalls.h"
#include "mmu.h"
-/*
- * This should probably be a config option. On 32-bit, it costs 1
- * page/gig of memory; on 64-bit its 2 pages/gig. If we want it to be
- * completely unbounded we can add another level to the p2m structure.
- */
-#define MAX_GUEST_PAGES (16ull * 1024*1024*1024 / PAGE_SIZE)
#define P2M_ENTRIES_PER_PAGE (PAGE_SIZE / sizeof(unsigned long))
-static unsigned long *p2m_top[MAX_GUEST_PAGES / P2M_ENTRIES_PER_PAGE];
+static unsigned long *p2m_top[MAX_DOMAIN_PAGES / P2M_ENTRIES_PER_PAGE];
static inline unsigned p2m_top_index(unsigned long pfn)
{
- BUG_ON(pfn >= MAX_GUEST_PAGES);
+ BUG_ON(pfn >= MAX_DOMAIN_PAGES);
return pfn / P2M_ENTRIES_PER_PAGE;
}
@@ -81,12 +75,9 @@
{
unsigned pfn;
unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
+ unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
- BUG_ON(xen_start_info->nr_pages >= MAX_GUEST_PAGES);
-
- for(pfn = 0;
- pfn < xen_start_info->nr_pages;
- pfn += P2M_ENTRIES_PER_PAGE) {
+ for(pfn = 0; pfn < max_pfn; pfn += P2M_ENTRIES_PER_PAGE) {
unsigned topidx = p2m_top_index(pfn);
p2m_top[topidx] = &mfn_list[pfn];
@@ -97,6 +88,9 @@
{
unsigned topidx, idx;
+ if (unlikely(pfn >= MAX_DOMAIN_PAGES))
+ return INVALID_P2M_ENTRY;
+
topidx = p2m_top_index(pfn);
if (p2m_top[topidx] == NULL)
return INVALID_P2M_ENTRY;
@@ -129,6 +123,11 @@
return;
}
+ if (unlikely(pfn >= MAX_DOMAIN_PAGES)) {
+ BUG_ON(mfn != INVALID_P2M_ENTRY);
+ return;
+ }
+
topidx = p2m_top_index(pfn);
if (p2m_top[topidx] == NULL) {
/* no need to allocate a page to store an invalid entry */