Commit 42ee1471 authored by Jeremy Fitzhardinge's avatar Jeremy Fitzhardinge
Browse files

xen: implement "extra" memory to reserve space for pages not present at boot 



When using the e820 map to get the initial pseudo-physical address space,
look for either Xen-provided memory which doesn't lie within an E820
region, or an E820 RAM region which extends beyond the Xen-provided
memory range.

Count these pages, and add them to a new "extra memory" range.  This range
has an E820 RAM range to describe it - so the kernel will allocate page
structures for it - but it is also marked reserved so that the kernel
will not attempt to use it.

The balloon driver can then add this range as a set of currently
ballooned-out pages, which can be used to extend the domain beyond its
original size.

Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
parent 35ae11fd

arch/x86/xen/setup.c

+27 −2
Original line number Diff line number Diff line
@@ -34,6 +34,26 @@ extern void xen_sysenter_target(void); 
extern void xen_syscall_target(void);

extern void xen_syscall32_target(void);



/* Amount of extra memory space we add to the e820 ranges */

phys_addr_t xen_extra_mem_start, xen_extra_mem_size;



static __init void xen_add_extra_mem(unsigned long pages)

{

	u64 size = (u64)pages * PAGE_SIZE;



	if (!pages)

		return;



	e820_add_region(xen_extra_mem_start + xen_extra_mem_size, size, E820_RAM);

	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);



	reserve_early(xen_extra_mem_start + xen_extra_mem_size,

		      xen_extra_mem_start + xen_extra_mem_size + size,

		      "XEN EXTRA");



	xen_extra_mem_size += size;

}



static unsigned long __init xen_release_chunk(phys_addr_t start_addr,

					      phys_addr_t end_addr)

{
@@ -105,7 +125,6 @@ static unsigned long __init xen_return_unused_memory(unsigned long max_pfn, 
/**

 * machine_specific_memory_setup - Hook for machine specific memory setup.

 **/



char * __init xen_memory_setup(void)

{

	static struct e820entry map[E820MAX] __initdata;
@@ -114,6 +133,7 @@ char * __init xen_memory_setup(void) 
	unsigned long long mem_end;

	int rc;

	struct xen_memory_map memmap;

	unsigned long extra_pages = 0;

	int i;



	max_pfn = min(MAX_DOMAIN_PAGES, max_pfn);
@@ -135,6 +155,7 @@ char * __init xen_memory_setup(void) 
	BUG_ON(rc);



	e820.nr_map = 0;

	xen_extra_mem_start = mem_end;

	for (i = 0; i < memmap.nr_entries; i++) {

		unsigned long long end = map[i].addr + map[i].size;

		if (map[i].type == E820_RAM) {
@@ -143,6 +164,8 @@ char * __init xen_memory_setup(void) 
			if (end > mem_end) {

				/* Truncate region to max_mem. */

				map[i].size -= end - mem_end;



				extra_pages += PFN_DOWN(end - mem_end);

			}

		}

		if (map[i].size > 0)
@@ -169,7 +192,9 @@ char * __init xen_memory_setup(void) 


	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);



	xen_return_unused_memory(xen_start_info->nr_pages, &e820);

	extra_pages += xen_return_unused_memory(xen_start_info->nr_pages, &e820);



	xen_add_extra_mem(extra_pages);



	return "Xen";

}

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