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Subject: Add fallback when XENMEM_exchange fails to replace contiguous region
From: jbeulich@novell.com
Patch-mainline: obsolete
References: 181869
This avoids losing precious special memory in places where any memory can be
used.
Index: 10.3-2007-10-22/arch/i386/mm/hypervisor.c
===================================================================
--- 10.3-2007-10-22.orig/arch/i386/mm/hypervisor.c 2007-10-22 13:49:28.000000000 +0200
+++ 10.3-2007-10-22/arch/i386/mm/hypervisor.c 2007-10-22 14:00:22.000000000 +0200
@@ -41,6 +41,7 @@
#include <xen/interface/memory.h>
#include <linux/module.h>
#include <linux/percpu.h>
+#include <linux/highmem.h>
#include <asm/tlbflush.h>
#ifdef CONFIG_X86_64
@@ -442,6 +443,83 @@ void xen_destroy_contiguous_region(unsig
BUG();
balloon_unlock(flags);
+
+ if (unlikely(!success)) {
+ /* Try hard to get the special memory back to Xen. */
+ exchange.in.extent_order = 0;
+ set_xen_guest_handle(exchange.in.extent_start, &in_frame);
+
+ for (i = 0; i < (1UL<<order); i++) {
+ struct page *page = alloc_page(__GFP_HIGHMEM);
+ unsigned long pfn;
+ mmu_update_t mmu;
+ unsigned int j = 0;
+
+ if (!page) {
+ printk(KERN_WARNING "Xen and kernel out of memory "
+ "while trying to release an order %u "
+ "contiguous region\n", order);
+ break;
+ }
+ pfn = page_to_pfn(page);
+
+ balloon_lock(flags);
+
+ if (!PageHighMem(page)) {
+ void *v = __va(pfn << PAGE_SHIFT);
+
+ scrub_pages(v, 1);
+ MULTI_update_va_mapping(cr_mcl + j, (unsigned long)v,
+ __pte_ma(0), UVMF_INVLPG|UVMF_ALL);
+ ++j;
+ }
+#ifdef CONFIG_XEN_SCRUB_PAGES
+ else {
+ scrub_pages(kmap(page), 1);
+ kunmap(page);
+ kmap_flush_unused();
+ }
+#endif
+
+ frame = pfn_to_mfn(pfn);
+ set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
+
+ MULTI_update_va_mapping(cr_mcl + j, vstart,
+ pfn_pte_ma(frame, PAGE_KERNEL),
+ UVMF_INVLPG|UVMF_ALL);
+ ++j;
+
+ pfn = __pa(vstart) >> PAGE_SHIFT;
+ set_phys_to_machine(pfn, frame);
+ if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+ mmu.ptr = ((uint64_t)frame << PAGE_SHIFT) | MMU_MACHPHYS_UPDATE;
+ mmu.val = pfn;
+ cr_mcl[j].op = __HYPERVISOR_mmu_update;
+ cr_mcl[j].args[0] = (unsigned long)&mmu;
+ cr_mcl[j].args[1] = 1;
+ cr_mcl[j].args[2] = 0;
+ cr_mcl[j].args[3] = DOMID_SELF;
+ ++j;
+ }
+
+ cr_mcl[j].op = __HYPERVISOR_memory_op;
+ cr_mcl[j].args[0] = XENMEM_decrease_reservation;
+ cr_mcl[j].args[1] = (unsigned long)&exchange.in;
+
+ if (HYPERVISOR_multicall(cr_mcl, j + 1))
+ BUG();
+ BUG_ON(cr_mcl[j].result != 1);
+ while (j--)
+ BUG_ON(cr_mcl[j].result != 0);
+
+ balloon_unlock(flags);
+
+ free_empty_pages(&page, 1);
+
+ in_frame++;
+ vstart += PAGE_SIZE;
+ }
+ }
}
EXPORT_SYMBOL_GPL(xen_destroy_contiguous_region);
Index: 10.3-2007-10-22/drivers/xen/balloon/balloon.c
===================================================================
--- 10.3-2007-10-22.orig/drivers/xen/balloon/balloon.c 2007-10-22 14:00:20.000000000 +0200
+++ 10.3-2007-10-22/drivers/xen/balloon/balloon.c 2007-10-22 14:00:22.000000000 +0200
@@ -680,7 +680,7 @@ struct page **alloc_empty_pages_and_page
goto out;
}
-void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages)
+static void _free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages, int free_vec)
{
unsigned long flags;
int i;
@@ -695,11 +695,24 @@ void free_empty_pages_and_pagevec(struct
}
balloon_unlock(flags);
- kfree(pagevec);
+ if (free_vec)
+ kfree(pagevec);
+ else
+ totalram_pages = bs.current_pages -= nr_pages;
schedule_work(&balloon_worker);
}
+void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages)
+{
+ _free_empty_pages_and_pagevec(pagevec, nr_pages, 1);
+}
+
+void free_empty_pages(struct page **pagevec, int nr_pages)
+{
+ _free_empty_pages_and_pagevec(pagevec, nr_pages, 0);
+}
+
void balloon_release_driver_page(struct page *page)
{
unsigned long flags;
Index: 10.3-2007-10-22/include/xen/balloon.h
===================================================================
--- 10.3-2007-10-22.orig/include/xen/balloon.h 2007-10-22 13:48:11.000000000 +0200
+++ 10.3-2007-10-22/include/xen/balloon.h 2007-10-22 14:00:22.000000000 +0200
@@ -44,6 +44,10 @@ void balloon_update_driver_allowance(lon
struct page **alloc_empty_pages_and_pagevec(int nr_pages);
void free_empty_pages_and_pagevec(struct page **pagevec, int nr_pages);
+/* Free an empty page range (not allocated through
+ alloc_empty_pages_and_pagevec), adding to the balloon. */
+void free_empty_pages(struct page **pagevec, int nr_pages);
+
void balloon_release_driver_page(struct page *page);
/*
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