svn commit: r258997 - stable/10/sys/dev/xen/balloon

Roger Pau Monné royger at FreeBSD.org
Thu Dec 5 18:09:49 UTC 2013


Author: royger
Date: Thu Dec  5 18:09:48 2013
New Revision: 258997
URL: http://svnweb.freebsd.org/changeset/base/258997

Log:
  MFC 258178:
  
  Improve robustness of the Xen balloon driver.
  
  sys/dev/xen/balloon/balloon.c:
  	Remove unused and commented out code.
  
  	Fix deadlock caused by performing a sleepable malloc
  	while holding the balloon mutex.
  
  	Perform proper accounting of the memory used by the domain.
  
  Submitted by:	Roger Pau Monné
  Sponsored by:	Citrix Systems R&D
  Reviewed by:	gibbs
  Approved by:	gibbs (mentor)
  Approved by:	re (gjb)

Modified:
  stable/10/sys/dev/xen/balloon/balloon.c
Directory Properties:
  stable/10/sys/   (props changed)

Modified: stable/10/sys/dev/xen/balloon/balloon.c
==============================================================================
--- stable/10/sys/dev/xen/balloon/balloon.c	Thu Dec  5 18:08:05 2013	(r258996)
+++ stable/10/sys/dev/xen/balloon/balloon.c	Thu Dec  5 18:09:48 2013	(r258997)
@@ -52,18 +52,13 @@ __FBSDID("$FreeBSD$");
 
 static MALLOC_DEFINE(M_BALLOON, "Balloon", "Xen Balloon Driver");
 
-struct mtx balloon_mutex;
+/* Convert from KB (as fetched from xenstore) to number of PAGES */
+#define KB_TO_PAGE_SHIFT	(PAGE_SHIFT - 10)
 
-/*
- * Protects atomic reservation decrease/increase against concurrent increases.
- * Also protects non-atomic updates of current_pages and driver_pages, and
- * balloon lists.
- */
-struct mtx balloon_lock;
+struct mtx balloon_mutex;
 
 /* We increase/decrease in batches which fit in a page */
 static unsigned long frame_list[PAGE_SIZE / sizeof(unsigned long)];
-#define ARRAY_SIZE(A)	(sizeof(A) / sizeof(A[0]))
 
 struct balloon_stats {
 	/* We aim for 'current allocation' == 'target allocation'. */
@@ -116,15 +111,21 @@ static void balloon_process(void *unused
 	printk(KERN_WARNING "xen_mem: " fmt, ##args)
 
 /* balloon_append: add the given page to the balloon. */
-static void 
+static int
 balloon_append(vm_page_t page)
 {
 	struct balloon_entry *entry;
 
-	entry = malloc(sizeof(struct balloon_entry), M_BALLOON, M_WAITOK);
+	mtx_assert(&balloon_mutex, MA_OWNED);
+
+	entry = malloc(sizeof(struct balloon_entry), M_BALLOON, M_NOWAIT);
+	if (!entry)
+		return (ENOMEM);
 	entry->page = page;
 	STAILQ_INSERT_HEAD(&ballooned_pages, entry, list);
 	bs.balloon_low++;
+
+	return (0);
 }
 
 /* balloon_retrieve: rescue a page from the balloon, if it is not empty. */
@@ -134,8 +135,10 @@ balloon_retrieve(void)
 	vm_page_t page;
 	struct balloon_entry *entry;
 
+	mtx_assert(&balloon_mutex, MA_OWNED);
+
 	if (STAILQ_EMPTY(&ballooned_pages))
-		return NULL;
+		return (NULL);
 
 	entry = STAILQ_FIRST(&ballooned_pages);
 	STAILQ_REMOVE_HEAD(&ballooned_pages, list);
@@ -145,7 +148,7 @@ balloon_retrieve(void)
 	
 	bs.balloon_low--;
 
-	return page;
+	return (page);
 }
 
 static unsigned long 
@@ -154,21 +157,22 @@ current_target(void)
 	unsigned long target = min(bs.target_pages, bs.hard_limit);
 	if (target > (bs.current_pages + bs.balloon_low + bs.balloon_high))
 		target = bs.current_pages + bs.balloon_low + bs.balloon_high;
-	return target;
+	return (target);
 }
 
 static unsigned long
 minimum_target(void)
 {
 #ifdef XENHVM
-#define max_pfn physmem
+#define max_pfn realmem
 #else
 #define max_pfn HYPERVISOR_shared_info->arch.max_pfn
 #endif
 	unsigned long min_pages, curr_pages = current_target();
 
 #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT))
-	/* Simple continuous piecewiese linear function:
+	/*
+	 * Simple continuous piecewiese linear function:
 	 *  max MiB -> min MiB	gradient
 	 *       0	   0
 	 *      16	  16
@@ -189,12 +193,10 @@ minimum_target(void)
 	else
 		min_pages = MB2PAGES(296) + (max_pfn >> 5);
 #undef MB2PAGES
+#undef max_pfn
 
 	/* Don't enforce growth */
-	return min(min_pages, curr_pages);
-#ifndef CONFIG_XEN
-#undef max_pfn
-#endif
+	return (min(min_pages, curr_pages));
 }
 
 static int 
@@ -210,10 +212,10 @@ increase_reservation(unsigned long nr_pa
 		.domid        = DOMID_SELF
 	};
 
-	if (nr_pages > ARRAY_SIZE(frame_list))
-		nr_pages = ARRAY_SIZE(frame_list);
+	mtx_assert(&balloon_mutex, MA_OWNED);
 
-	mtx_lock(&balloon_lock);
+	if (nr_pages > nitems(frame_list))
+		nr_pages = nitems(frame_list);
 
 	for (entry = STAILQ_FIRST(&ballooned_pages), i = 0;
 	     i < nr_pages; i++, entry = STAILQ_NEXT(entry, list)) {
@@ -253,33 +255,14 @@ increase_reservation(unsigned long nr_pa
 
 		set_phys_to_machine(pfn, frame_list[i]);
 
-#if 0
-#ifndef XENHVM
-		/* Link back into the page tables if not highmem. */
-		if (pfn < max_low_pfn) {
-			int ret;
-			ret = HYPERVISOR_update_va_mapping(
-				(unsigned long)__va(pfn << PAGE_SHIFT),
-				pfn_pte_ma(frame_list[i], PAGE_KERNEL),
-				0);
-			PASSING(ret == 0,
-			    ("HYPERVISOR_update_va_mapping failed"));
-		}
-#endif
-#endif
-
-		/* Relinquish the page back to the allocator. */
 		vm_page_unwire(page, 0);
 		vm_page_free(page);
 	}
 
 	bs.current_pages += nr_pages;
-	//totalram_pages = bs.current_pages;
 
  out:
-	mtx_unlock(&balloon_lock);
-
-	return 0;
+	return (0);
 }
 
 static int
@@ -295,8 +278,10 @@ decrease_reservation(unsigned long nr_pa
 		.domid        = DOMID_SELF
 	};
 
-	if (nr_pages > ARRAY_SIZE(frame_list))
-		nr_pages = ARRAY_SIZE(frame_list);
+	mtx_assert(&balloon_mutex, MA_OWNED);
+
+	if (nr_pages > nitems(frame_list))
+		nr_pages = nitems(frame_list);
 
 	for (i = 0; i < nr_pages; i++) {
 		if ((page = vm_page_alloc(NULL, 0, 
@@ -310,39 +295,15 @@ decrease_reservation(unsigned long nr_pa
 		pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT);
 		frame_list[i] = PFNTOMFN(pfn);
 
-#if 0
-		if (!PageHighMem(page)) {
-			v = phys_to_virt(pfn << PAGE_SHIFT);
-			scrub_pages(v, 1);
-#ifdef CONFIG_XEN
-			ret = HYPERVISOR_update_va_mapping(
-				(unsigned long)v, __pte_ma(0), 0);
-			BUG_ON(ret);
-#endif
-		}
-#endif
-#ifdef CONFIG_XEN_SCRUB_PAGES
-		else {
-			v = kmap(page);
-			scrub_pages(v, 1);
-			kunmap(page);
-		}
-#endif
-	}
-
-#ifdef CONFIG_XEN
-	/* Ensure that ballooned highmem pages don't have kmaps. */
-	kmap_flush_unused();
-	flush_tlb_all();
-#endif
-
-	mtx_lock(&balloon_lock);
-
-	/* No more mappings: invalidate P2M and add to balloon. */
-	for (i = 0; i < nr_pages; i++) {
-		pfn = MFNTOPFN(frame_list[i]);
 		set_phys_to_machine(pfn, INVALID_P2M_ENTRY);
-		balloon_append(PHYS_TO_VM_PAGE(pfn << PAGE_SHIFT));
+		if (balloon_append(page) != 0) {
+			vm_page_unwire(page, 0);
+			vm_page_free(page);
+
+			nr_pages = i;
+			need_sleep = 1;
+			break;
+		}
 	}
 
 	set_xen_guest_handle(reservation.extent_start, frame_list);
@@ -351,9 +312,6 @@ decrease_reservation(unsigned long nr_pa
 	KASSERT(ret == nr_pages, ("HYPERVISOR_memory_op failed"));
 
 	bs.current_pages -= nr_pages;
-	//totalram_pages = bs.current_pages;
-
-	mtx_unlock(&balloon_lock);
 
 	return (need_sleep);
 }
@@ -425,11 +383,11 @@ watch_target(struct xs_watch *watch,
 		return;
 	} 
         
-	/* The given memory/target value is in KiB, so it needs converting to
-	   pages.  PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
-	*/
-	set_new_target(new_target >> (PAGE_SHIFT - 10));
-    
+	/*
+	 * The given memory/target value is in KiB, so it needs converting to
+	 * pages.  PAGE_SHIFT converts bytes to pages, hence PAGE_SHIFT - 10.
+	 */
+	set_new_target(new_target >> KB_TO_PAGE_SHIFT);
 }
 
 static void 
@@ -461,13 +419,12 @@ balloon_init(void *arg)
 	if (!is_running_on_xen())
 		return;
 
-	mtx_init(&balloon_lock, "balloon_lock", NULL, MTX_DEF);
 	mtx_init(&balloon_mutex, "balloon_mutex", NULL, MTX_DEF);
 
 #ifndef XENHVM
 	bs.current_pages = min(xen_start_info->nr_pages, max_pfn);
 #else
-	bs.current_pages = physmem;
+	bs.current_pages = realmem;
 #endif
 	bs.target_pages  = bs.current_pages;
 	bs.balloon_low   = 0;
@@ -497,76 +454,7 @@ void balloon_update_driver_allowance(lon
 void 
 balloon_update_driver_allowance(long delta)
 {
-	mtx_lock(&balloon_lock);
+	mtx_lock(&balloon_mutex);
 	bs.driver_pages += delta;
-	mtx_unlock(&balloon_lock);
-}
-
-#if 0
-static int dealloc_pte_fn(
-	pte_t *pte, struct page *pte_page, unsigned long addr, void *data)
-{
-	unsigned long mfn = pte_mfn(*pte);
-	int ret;
-	struct xen_memory_reservation reservation = {
-		.extent_start = &mfn,
-		.nr_extents   = 1,
-		.extent_order = 0,
-		.domid        = DOMID_SELF
-	};
-	set_pte_at(&init_mm, addr, pte, __pte_ma(0));
-	set_phys_to_machine(__pa(addr) >> PAGE_SHIFT, INVALID_P2M_ENTRY);
-	ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation);
-	KASSERT(ret == 1, ("HYPERVISOR_memory_op failed"));
-	return 0;
-}
-
-#endif
-
-#if 0
-vm_page_t
-balloon_alloc_empty_page_range(unsigned long nr_pages)
-{
-	vm_page_t pages;
-	int i, rc;
-	unsigned long *mfn_list;
-	struct xen_memory_reservation reservation = {
-		.address_bits = 0,
-		.extent_order = 0,
-		.domid        = DOMID_SELF
-	};
-
-	pages = vm_page_alloc_contig(nr_pages, 0, -1, 4, 4)
-	if (pages == NULL)
-		return NULL;
-	
-	mfn_list = malloc(nr_pages*sizeof(unsigned long), M_DEVBUF, M_WAITOK);
-	
-	for (i = 0; i < nr_pages; i++) {
-		mfn_list[i] = PFNTOMFN(VM_PAGE_TO_PHYS(pages[i]) >> PAGE_SHIFT);
-		PFNTOMFN(i) = INVALID_P2M_ENTRY;
-		reservation.extent_start = mfn_list;
-		reservation.nr_extents = nr_pages;
-		rc = HYPERVISOR_memory_op(XENMEM_decrease_reservation,
-		    &reservation);
-		KASSERT(rc == nr_pages, ("HYPERVISOR_memory_op failed"));
-	}
-
-	current_pages -= nr_pages;
-
-	wakeup(balloon_process);
-
-	return pages;
-}
-
-void 
-balloon_dealloc_empty_page_range(vm_page_t page, unsigned long nr_pages)
-{
-	unsigned long i;
-
-	for (i = 0; i < nr_pages; i++)
-		balloon_append(page + i);
-
-	wakeup(balloon_process);
+	mtx_unlock(&balloon_mutex);
 }
-#endif


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