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Commit cd9151e2 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Konrad Rzeszutek Wilk
Browse files

xen/balloon: set a mapping for ballooned out pages 

Currently ballooned out pages are mapped to 0 and have INVALID_P2M_ENTRY
in the p2m. These ballooned out pages are used to map foreign grants
by gntdev and blkback (see alloc_xenballooned_pages).

Allocate a page per cpu and map all the ballooned out pages to the
corresponding mfn. Set the p2m accordingly. This way reading from a
ballooned out page won't cause a kernel crash (see
http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html

).

Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
CC: alex@alex.org.uk
CC: dcrisan@flexiant.com
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 73cc4bb0

drivers/xen/balloon.c

+66 −3
Original line number Original line Diff line number Diff line
@@ -38,6 +38,7 @@ 




#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt

#define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt





#include <linux/cpu.h>

#include <linux/kernel.h>

#include <linux/kernel.h>

#include <linux/sched.h>

#include <linux/sched.h>

#include <linux/errno.h>

#include <linux/errno.h>
@@ -52,6 +53,7 @@ 
#include <linux/notifier.h>

#include <linux/notifier.h>

#include <linux/memory.h>

#include <linux/memory.h>

#include <linux/memory_hotplug.h>

#include <linux/memory_hotplug.h>

#include <linux/percpu-defs.h>





#include <asm/page.h>

#include <asm/page.h>

#include <asm/pgalloc.h>

#include <asm/pgalloc.h>
@@ -90,6 +92,8 @@ EXPORT_SYMBOL_GPL(balloon_stats); 




/* We increase/decrease in batches which fit in a page */

/* 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[PAGE_SIZE / sizeof(unsigned long)];

static DEFINE_PER_CPU(struct page *, balloon_scratch_page);







/* List of ballooned pages, threaded through the mem_map array. */

/* List of ballooned pages, threaded through the mem_map array. */

static LIST_HEAD(ballooned_pages);

static LIST_HEAD(ballooned_pages);
@@ -412,7 +416,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) 
		if (xen_pv_domain() && !PageHighMem(page)) {

		if (xen_pv_domain() && !PageHighMem(page)) {

			ret = HYPERVISOR_update_va_mapping(

			ret = HYPERVISOR_update_va_mapping(

				(unsigned long)__va(pfn << PAGE_SHIFT),

				(unsigned long)__va(pfn << PAGE_SHIFT),

				__pte_ma(0), 0);

				pfn_pte(page_to_pfn(__get_cpu_var(balloon_scratch_page)),

					PAGE_KERNEL_RO), 0);

			BUG_ON(ret);

			BUG_ON(ret);

		}

		}

#endif

#endif
@@ -425,7 +430,8 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) 
	/* No more mappings: invalidate P2M and add to balloon. */

	/* No more mappings: invalidate P2M and add to balloon. */

	for (i = 0; i < nr_pages; i++) {

	for (i = 0; i < nr_pages; i++) {

		pfn = mfn_to_pfn(frame_list[i]);

		pfn = mfn_to_pfn(frame_list[i]);

		__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);

		__set_phys_to_machine(pfn,

				pfn_to_mfn(page_to_pfn(__get_cpu_var(balloon_scratch_page))));

		balloon_append(pfn_to_page(pfn));

		balloon_append(pfn_to_page(pfn));

	}

	}
@@ -480,6 +486,18 @@ static void balloon_process(struct work_struct *work) 
	mutex_unlock(&balloon_mutex);

	mutex_unlock(&balloon_mutex);

}

}





struct page *get_balloon_scratch_page(void)

{

	struct page *ret = get_cpu_var(balloon_scratch_page);

	BUG_ON(ret == NULL);

	return ret;

}



void put_balloon_scratch_page(void)

{

	put_cpu_var(balloon_scratch_page);

}



/* Resets the Xen limit, sets new target, and kicks off processing. */

/* Resets the Xen limit, sets new target, and kicks off processing. */

void balloon_set_new_target(unsigned long target)

void balloon_set_new_target(unsigned long target)

{

{
@@ -573,13 +591,47 @@ static void __init balloon_add_region(unsigned long start_pfn, 
	}

	}

}

}





static int __cpuinit balloon_cpu_notify(struct notifier_block *self,

				    unsigned long action, void *hcpu)

{

	int cpu = (long)hcpu;

	switch (action) {

	case CPU_UP_PREPARE:

		if (per_cpu(balloon_scratch_page, cpu) != NULL)

			break;

		per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);

		if (per_cpu(balloon_scratch_page, cpu) == NULL) {

			pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);

			return NOTIFY_BAD;

		}

		break;

	default:

		break;

	}

	return NOTIFY_OK;

}



static struct notifier_block balloon_cpu_notifier __cpuinitdata = {

	.notifier_call	= balloon_cpu_notify,

};



static int __init balloon_init(void)

static int __init balloon_init(void)

{

{

	int i;

	int i, cpu;





	if (!xen_domain())

	if (!xen_domain())

		return -ENODEV;

		return -ENODEV;





	for_each_online_cpu(cpu)

	{

		per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);

		if (per_cpu(balloon_scratch_page, cpu) == NULL) {

			pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);

			return -ENOMEM;

		}

	}

	register_cpu_notifier(&balloon_cpu_notifier);



	pr_info("Initialising balloon driver\n");

	pr_info("Initialising balloon driver\n");





	balloon_stats.current_pages = xen_pv_domain()

	balloon_stats.current_pages = xen_pv_domain()
@@ -616,4 +668,15 @@ static int __init balloon_init(void) 




subsys_initcall(balloon_init);

subsys_initcall(balloon_init);





static int __init balloon_clear(void)

{

	int cpu;



	for_each_possible_cpu(cpu)

		per_cpu(balloon_scratch_page, cpu) = NULL;



	return 0;

}

early_initcall(balloon_clear);



MODULE_LICENSE("GPL");
 
MODULE_LICENSE("GPL");

include/xen/balloon.h

+3 −0
Original line number Original line Diff line number Diff line
@@ -29,6 +29,9 @@ int alloc_xenballooned_pages(int nr_pages, struct page **pages, 
		bool highmem);

		bool highmem);

void free_xenballooned_pages(int nr_pages, struct page **pages);

void free_xenballooned_pages(int nr_pages, struct page **pages);





struct page *get_balloon_scratch_page(void);

void put_balloon_scratch_page(void);



struct device;

struct device;

#ifdef CONFIG_XEN_SELFBALLOONING

#ifdef CONFIG_XEN_SELFBALLOONING

extern int register_xen_selfballooning(struct device *dev);

extern int register_xen_selfballooning(struct device *dev);