From 68e58ea7edb30b90468e0d0d609f9dfa6b8dd9d5 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Roger=20Pau=20Monn=C3=A9?= Date: Wed, 25 Jun 2014 09:51:08 +0000 Subject: [PATCH] xen/virtio: fix balloon drivers to not mark pages as WIRED Prevent the Xen and VirtIO balloon drivers from marking pages as wired. This prevents them from increasing the system wired page count, which can lead to mlock failing because of hitting the limit in vm.max_wired. In the Xen case make sure pages are zeroed before giving them back to the hypervisor, or else we might be leaking data. Also remove the balloon_{append/retrieve} and link pages directly into the ballooned_pages queue using the plinks.q field in the page struct. Sponsored by: Citrix Systems R&D Reviewed by: kib, bryanv Approved by: gibbs dev/virtio/balloon/virtio_balloon.c: - Don't allocate pages with VM_ALLOC_WIRED. dev/xen/balloon/balloon.c: - Don't allocate pages with VM_ALLOC_WIRED. - Make sure pages are zeroed before giving them back to the hypervisor. - Remove the balloon_entry struct and the balloon_{append/retrieve} functions and use the page plinks.q entry to link the pages directly into the ballooned_pages queue. --- sys/dev/virtio/balloon/virtio_balloon.c | 4 +- sys/dev/xen/balloon/balloon.c | 89 +++++++------------------ 2 files changed, 25 insertions(+), 68 deletions(-) diff --git a/sys/dev/virtio/balloon/virtio_balloon.c b/sys/dev/virtio/balloon/virtio_balloon.c index d540099316f..6d00ef38bfa 100644 --- a/sys/dev/virtio/balloon/virtio_balloon.c +++ b/sys/dev/virtio/balloon/virtio_balloon.c @@ -438,8 +438,7 @@ vtballoon_alloc_page(struct vtballoon_softc *sc) { vm_page_t m; - m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_WIRED | - VM_ALLOC_NOOBJ); + m = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ); if (m != NULL) sc->vtballoon_current_npages++; @@ -450,7 +449,6 @@ static void vtballoon_free_page(struct vtballoon_softc *sc, vm_page_t m) { - vm_page_unwire(m, PQ_INACTIVE); vm_page_free(m); sc->vtballoon_current_npages--; } diff --git a/sys/dev/xen/balloon/balloon.c b/sys/dev/xen/balloon/balloon.c index fa56c863656..6503a0060fa 100644 --- a/sys/dev/xen/balloon/balloon.c +++ b/sys/dev/xen/balloon/balloon.c @@ -94,13 +94,8 @@ SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, low_mem, CTLFLAG_RD, SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, high_mem, CTLFLAG_RD, &bs.balloon_high, 0, "High-mem balloon"); -struct balloon_entry { - vm_page_t page; - STAILQ_ENTRY(balloon_entry) list; -}; - /* List of ballooned pages, threaded through the mem_map array. */ -static STAILQ_HEAD(,balloon_entry) ballooned_pages; +static TAILQ_HEAD(,vm_page) ballooned_pages; /* Main work function, always executed in process context. */ static void balloon_process(void *unused); @@ -110,47 +105,6 @@ static void balloon_process(void *unused); #define WPRINTK(fmt, args...) \ printk(KERN_WARNING "xen_mem: " fmt, ##args) -/* balloon_append: add the given page to the balloon. */ -static int -balloon_append(vm_page_t page) -{ - struct balloon_entry *entry; - - 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. */ -static vm_page_t -balloon_retrieve(void) -{ - vm_page_t page; - struct balloon_entry *entry; - - mtx_assert(&balloon_mutex, MA_OWNED); - - if (STAILQ_EMPTY(&ballooned_pages)) - return (NULL); - - entry = STAILQ_FIRST(&ballooned_pages); - STAILQ_REMOVE_HEAD(&ballooned_pages, list); - - page = entry->page; - free(entry, M_BALLOON); - - bs.balloon_low--; - - return (page); -} - static unsigned long current_target(void) { @@ -203,7 +157,6 @@ static int increase_reservation(unsigned long nr_pages) { unsigned long pfn, i; - struct balloon_entry *entry; vm_page_t page; long rc; struct xen_memory_reservation reservation = { @@ -217,10 +170,9 @@ increase_reservation(unsigned long nr_pages) 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)) { - KASSERT(entry, ("ballooned_pages list corrupt")); - page = entry->page; + for (page = TAILQ_FIRST(&ballooned_pages), i = 0; + i < nr_pages; i++, page = TAILQ_NEXT(page, plinks.q)) { + KASSERT(page != NULL, ("ballooned_pages list corrupt")); frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); } @@ -245,8 +197,10 @@ increase_reservation(unsigned long nr_pages) } for (i = 0; i < nr_pages; i++) { - page = balloon_retrieve(); - KASSERT(page, ("balloon_retrieve failed")); + page = TAILQ_FIRST(&ballooned_pages); + KASSERT(page != NULL, ("Unable to get ballooned page")); + TAILQ_REMOVE(&ballooned_pages, page, plinks.q); + bs.balloon_low--; pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); KASSERT((xen_feature(XENFEAT_auto_translated_physmap) || @@ -255,7 +209,6 @@ increase_reservation(unsigned long nr_pages) set_phys_to_machine(pfn, frame_list[i]); - vm_page_unwire(page, PQ_INACTIVE); vm_page_free(page); } @@ -286,24 +239,29 @@ decrease_reservation(unsigned long nr_pages) for (i = 0; i < nr_pages; i++) { if ((page = vm_page_alloc(NULL, 0, VM_ALLOC_NORMAL | VM_ALLOC_NOOBJ | - VM_ALLOC_WIRED | VM_ALLOC_ZERO)) == NULL) { + VM_ALLOC_ZERO)) == NULL) { nr_pages = i; need_sleep = 1; break; } + if ((page->flags & PG_ZERO) == 0) { + /* + * Zero the page, or else we might be leaking + * important data to other domains on the same + * host. Xen doesn't scrub ballooned out memory + * pages, the guest is in charge of making + * sure that no information is leaked. + */ + pmap_zero_page(page); + } + pfn = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); frame_list[i] = PFNTOMFN(pfn); set_phys_to_machine(pfn, INVALID_P2M_ENTRY); - if (balloon_append(page) != 0) { - vm_page_unwire(page, PQ_INACTIVE); - vm_page_free(page); - - nr_pages = i; - need_sleep = 1; - break; - } + TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); + bs.balloon_low++; } set_xen_guest_handle(reservation.extent_start, frame_list); @@ -438,7 +396,8 @@ balloon_init(void *arg) /* Initialise the balloon with excess memory space. */ for (pfn = xen_start_info->nr_pages; pfn < max_pfn; pfn++) { page = PHYS_TO_VM_PAGE(pfn << PAGE_SHIFT); - balloon_append(page); + TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); + bs.balloon_low++; } #undef max_pfn #endif