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authorDavid Vrabel <david.vrabel@citrix.com>2015-01-05 17:06:01 +0000
committerDavid Vrabel <david.vrabel@citrix.com>2015-01-28 14:03:10 +0000
commit0bb599fd30108883b00c7d4a226eeb49111e6932 (patch)
treee7939c55ff9b95a2eb180884bea213c1b78eb863 /drivers/xen
parent853d0289340026b30f93fd0e768340221d4e605c (diff)
xen: remove scratch frames for ballooned pages and m2p override
The scratch frame mappings for ballooned pages and the m2p override are broken. Remove them in preparation for replacing them with simpler mechanisms that works. The scratch pages did not ensure that the page was not in use. In particular, the foreign page could still be in use by hardware. If the guest reused the frame the hardware could read or write that frame. The m2p override did not handle the same frame being granted by two different grant references. Trying an M2P override lookup in this case is impossible. With the m2p override removed, the grant map/unmap for the kernel mappings (for x86 PV) can be easily batched in set_foreign_p2m_mapping() and clear_foreign_p2m_mapping(). Signed-off-by: David Vrabel <david.vrabel@citrix.com> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/balloon.c86
1 files changed, 2 insertions, 84 deletions
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 3860d02729dc..0b52d92cb2e5 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -92,7 +92,6 @@ 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 DEFINE_PER_CPU(struct page *, balloon_scratch_page);
/* List of ballooned pages, threaded through the mem_map array. */
@@ -423,22 +422,12 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp)
page = pfn_to_page(pfn);
#ifdef CONFIG_XEN_HAVE_PVMMU
- /*
- * Ballooned out frames are effectively replaced with
- * a scratch frame. Ensure direct mappings and the
- * p2m are consistent.
- */
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
if (!PageHighMem(page)) {
- struct page *scratch_page = get_balloon_scratch_page();
-
ret = HYPERVISOR_update_va_mapping(
(unsigned long)__va(pfn << PAGE_SHIFT),
- pfn_pte(page_to_pfn(scratch_page),
- PAGE_KERNEL_RO), 0);
+ __pte_ma(0), 0);
BUG_ON(ret);
-
- put_balloon_scratch_page();
}
__set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
}
@@ -500,18 +489,6 @@ static void balloon_process(struct work_struct *work)
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. */
void balloon_set_new_target(unsigned long target)
{
@@ -605,61 +582,13 @@ static void __init balloon_add_region(unsigned long start_pfn,
}
}
-static int alloc_balloon_scratch_page(int cpu)
-{
- if (per_cpu(balloon_scratch_page, cpu) != NULL)
- return 0;
-
- 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;
- }
-
- return 0;
-}
-
-
-static int balloon_cpu_notify(struct notifier_block *self,
- unsigned long action, void *hcpu)
-{
- int cpu = (long)hcpu;
- switch (action) {
- case CPU_UP_PREPARE:
- if (alloc_balloon_scratch_page(cpu))
- return NOTIFY_BAD;
- break;
- default:
- break;
- }
- return NOTIFY_OK;
-}
-
-static struct notifier_block balloon_cpu_notifier = {
- .notifier_call = balloon_cpu_notify,
-};
-
static int __init balloon_init(void)
{
- int i, cpu;
+ int i;
if (!xen_domain())
return -ENODEV;
- if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- register_cpu_notifier(&balloon_cpu_notifier);
-
- get_online_cpus();
- for_each_online_cpu(cpu) {
- if (alloc_balloon_scratch_page(cpu)) {
- put_online_cpus();
- unregister_cpu_notifier(&balloon_cpu_notifier);
- return -ENOMEM;
- }
- }
- put_online_cpus();
- }
-
pr_info("Initialising balloon driver\n");
balloon_stats.current_pages = xen_pv_domain()
@@ -696,15 +625,4 @@ static int __init balloon_init(void)
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");