/****************************************************************************** * balloon.c * * Xen balloon driver - enables returning/claiming memory to/from Xen. * * Copyright (c) 2003, B Dragovic * Copyright (c) 2003-2004, M Williamson, K Fraser * Copyright (c) 2005 Dan M. Smith, IBM Corporation * * This file may be distributed separately from the Linux kernel, or * incorporated into other software packages, subject to the following license: * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this source file (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, copy, modify, * merge, publish, distribute, sublicense, and/or sell copies of the Software, * and to permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS * IN THE SOFTWARE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include static MALLOC_DEFINE(M_BALLOON, "Balloon", "Xen Balloon Driver"); /* Convert from KB (as fetched from xenstore) to number of PAGES */ #define KB_TO_PAGE_SHIFT (PAGE_SHIFT - 10) struct mtx balloon_mutex; /* We increase/decrease in batches which fit in a page */ static xen_pfn_t frame_list[PAGE_SIZE / sizeof(xen_pfn_t)]; struct balloon_stats { /* We aim for 'current allocation' == 'target allocation'. */ unsigned long current_pages; unsigned long target_pages; /* We may hit the hard limit in Xen. If we do then we remember it. */ unsigned long hard_limit; /* * Drivers may alter the memory reservation independently, but they * must inform the balloon driver so we avoid hitting the hard limit. */ unsigned long driver_pages; /* Number of pages in high- and low-memory balloons. */ unsigned long balloon_low; unsigned long balloon_high; }; static struct balloon_stats balloon_stats; #define bs balloon_stats SYSCTL_DECL(_dev_xen); static SYSCTL_NODE(_dev_xen, OID_AUTO, balloon, CTLFLAG_RD | CTLFLAG_MPSAFE, NULL, "Balloon"); SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, current, CTLFLAG_RD, &bs.current_pages, 0, "Current allocation"); SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, target, CTLFLAG_RD, &bs.target_pages, 0, "Target allocation"); SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, driver_pages, CTLFLAG_RD, &bs.driver_pages, 0, "Driver pages"); SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, hard_limit, CTLFLAG_RD, &bs.hard_limit, 0, "Xen hard limit"); SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, low_mem, CTLFLAG_RD, &bs.balloon_low, 0, "Low-mem balloon"); SYSCTL_ULONG(_dev_xen_balloon, OID_AUTO, high_mem, CTLFLAG_RD, &bs.balloon_high, 0, "High-mem balloon"); /* List of ballooned pages, threaded through the mem_map array. */ static TAILQ_HEAD(,vm_page) ballooned_pages; /* Main work function, always executed in process context. */ static void balloon_process(void *unused); #define IPRINTK(fmt, args...) \ printk(KERN_INFO "xen_mem: " fmt, ##args) #define WPRINTK(fmt, args...) \ printk(KERN_WARNING "xen_mem: " fmt, ##args) static unsigned long 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); } static unsigned long minimum_target(void) { unsigned long min_pages, curr_pages = current_target(); #define MB2PAGES(mb) ((mb) << (20 - PAGE_SHIFT)) /* * Simple continuous piecewiese linear function: * max MiB -> min MiB gradient * 0 0 * 16 16 * 32 24 * 128 72 (1/2) * 512 168 (1/4) * 2048 360 (1/8) * 8192 552 (1/32) * 32768 1320 * 131072 4392 */ if (realmem < MB2PAGES(128)) min_pages = MB2PAGES(8) + (realmem >> 1); else if (realmem < MB2PAGES(512)) min_pages = MB2PAGES(40) + (realmem >> 2); else if (realmem < MB2PAGES(2048)) min_pages = MB2PAGES(104) + (realmem >> 3); else min_pages = MB2PAGES(296) + (realmem >> 5); #undef MB2PAGES /* Don't enforce growth */ return (min(min_pages, curr_pages)); } static int increase_reservation(unsigned long nr_pages) { unsigned long i; vm_page_t page; long rc; struct xen_memory_reservation reservation = { .address_bits = 0, .extent_order = 0, .domid = DOMID_SELF }; mtx_assert(&balloon_mutex, MA_OWNED); if (nr_pages > nitems(frame_list)) nr_pages = nitems(frame_list); 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); } set_xen_guest_handle(reservation.extent_start, frame_list); reservation.nr_extents = nr_pages; rc = HYPERVISOR_memory_op( XENMEM_populate_physmap, &reservation); if (rc < nr_pages) { if (rc > 0) { int ret; /* We hit the Xen hard limit: reprobe. */ reservation.nr_extents = rc; ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); KASSERT(ret == rc, ("HYPERVISOR_memory_op failed")); } if (rc >= 0) bs.hard_limit = (bs.current_pages + rc - bs.driver_pages); goto out; } for (i = 0; i < nr_pages; i++) { page = TAILQ_FIRST(&ballooned_pages); KASSERT(page != NULL, ("Unable to get ballooned page")); TAILQ_REMOVE(&ballooned_pages, page, plinks.q); bs.balloon_low--; KASSERT(xen_feature(XENFEAT_auto_translated_physmap), ("auto translated physmap but mapping is valid")); vm_page_free(page); } bs.current_pages += nr_pages; out: return (0); } static int decrease_reservation(unsigned long nr_pages) { unsigned long i; vm_page_t page; int need_sleep = 0; int ret; struct xen_memory_reservation reservation = { .address_bits = 0, .extent_order = 0, .domid = DOMID_SELF }; mtx_assert(&balloon_mutex, MA_OWNED); if (nr_pages > nitems(frame_list)) nr_pages = nitems(frame_list); for (i = 0; i < nr_pages; i++) { /* * 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. */ if ((page = vm_page_alloc_noobj(VM_ALLOC_ZERO)) == NULL) { nr_pages = i; need_sleep = 1; break; } frame_list[i] = (VM_PAGE_TO_PHYS(page) >> PAGE_SHIFT); TAILQ_INSERT_HEAD(&ballooned_pages, page, plinks.q); bs.balloon_low++; } set_xen_guest_handle(reservation.extent_start, frame_list); reservation.nr_extents = nr_pages; ret = HYPERVISOR_memory_op(XENMEM_decrease_reservation, &reservation); KASSERT(ret == nr_pages, ("HYPERVISOR_memory_op failed")); bs.current_pages -= nr_pages; return (need_sleep); } /* * We avoid multiple worker processes conflicting via the balloon mutex. * We may of course race updates of the target counts (which are protected * by the balloon lock), or with changes to the Xen hard limit, but we will * recover from these in time. */ static void balloon_process(void *unused) { int need_sleep = 0; long credit; mtx_lock(&balloon_mutex); for (;;) { int sleep_time; do { credit = current_target() - bs.current_pages; if (credit > 0) need_sleep = (increase_reservation(credit) != 0); if (credit < 0) need_sleep = (decrease_reservation(-credit) != 0); } while ((credit != 0) && !need_sleep); /* Schedule more work if there is some still to be done. */ if (current_target() != bs.current_pages) sleep_time = hz; else sleep_time = 0; msleep(balloon_process, &balloon_mutex, 0, "balloon", sleep_time); } mtx_unlock(&balloon_mutex); } /* Resets the Xen limit, sets new target, and kicks off processing. */ static void set_new_target(unsigned long target) { /* No need for lock. Not read-modify-write updates. */ bs.hard_limit = ~0UL; bs.target_pages = max(target, minimum_target()); wakeup(balloon_process); } static struct xs_watch target_watch = { .node = "memory/target", .max_pending = 1, }; /* React to a change in the target key */ static void watch_target(struct xs_watch *watch, const char **vec, unsigned int len) { unsigned long long new_target; int err; err = xs_scanf(XST_NIL, "memory", "target", NULL, "%llu", &new_target); if (err) { /* This is ok (for domain0 at least) - so just return */ 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 >> KB_TO_PAGE_SHIFT); } /*------------------ Private Device Attachment Functions --------------------*/ /** * \brief Identify instances of this device type in the system. * * \param driver The driver performing this identify action. * \param parent The NewBus parent device for any devices this method adds. */ static void xenballoon_identify(driver_t *driver __unused, device_t parent) { /* * A single device instance for our driver is always present * in a system operating under Xen. */ BUS_ADD_CHILD(parent, 0, driver->name, 0); } /** * \brief Probe for the existence of the Xen Balloon device * * \param dev NewBus device_t for this Xen control instance. * * \return Always returns 0 indicating success. */ static int xenballoon_probe(device_t dev) { device_set_desc(dev, "Xen Balloon Device"); return (0); } /** * \brief Attach the Xen Balloon device. * * \param dev NewBus device_t for this Xen control instance. * * \return On success, 0. Otherwise an errno value indicating the * type of failure. */ static int xenballoon_attach(device_t dev) { int err; mtx_init(&balloon_mutex, "balloon_mutex", NULL, MTX_DEF); bs.current_pages = realmem; bs.target_pages = bs.current_pages; bs.balloon_low = 0; bs.balloon_high = 0; bs.driver_pages = 0UL; bs.hard_limit = ~0UL; kproc_create(balloon_process, NULL, NULL, 0, 0, "balloon"); target_watch.callback = watch_target; err = xs_register_watch(&target_watch); if (err) device_printf(dev, "xenballon: failed to set balloon watcher\n"); return (err); } /*-------------------- Private Device Attachment Data -----------------------*/ static device_method_t xenballoon_methods[] = { /* Device interface */ DEVMETHOD(device_identify, xenballoon_identify), DEVMETHOD(device_probe, xenballoon_probe), DEVMETHOD(device_attach, xenballoon_attach), DEVMETHOD_END }; DEFINE_CLASS_0(xenballoon, xenballoon_driver, xenballoon_methods, 0); devclass_t xenballoon_devclass; DRIVER_MODULE(xenballoon, xenstore, xenballoon_driver, xenballoon_devclass, NULL, NULL);