@@ -15,6 +15,7 @@
#include "qemu/osdep.h"
#include <sys/ioctl.h>
+#include <poll.h>
#include <linux/kvm.h>
@@ -78,6 +79,25 @@ struct KVMParkedVcpu {
QLIST_ENTRY(KVMParkedVcpu) node;
};
+enum KVMDirtyRingReaperState {
+ KVM_DIRTY_RING_REAPER_NONE = 0,
+ /* The reaper is sleeping */
+ KVM_DIRTY_RING_REAPER_WAIT,
+ /* The reaper is reaping for dirty pages */
+ KVM_DIRTY_RING_REAPER_REAPING,
+};
+
+/*
+ * KVM reaper instance, responsible for collecting the KVM dirty bits
+ * via the dirty ring.
+ */
+struct KVMDirtyRingReaper {
+ /* The reaper thread */
+ QemuThread reaper_thr;
+ volatile uint64_t reaper_iteration; /* iteration number of reaper thr */
+ volatile enum KVMDirtyRingReaperState reaper_state; /* reap thr state */
+};
+
struct KVMState
{
AccelState parent_obj;
@@ -128,6 +148,7 @@ struct KVMState
} *as;
uint64_t kvm_dirty_ring_bytes; /* Size of the per-vcpu dirty ring */
uint32_t kvm_dirty_ring_size; /* Number of dirty GFNs per ring */
+ struct KVMDirtyRingReaper reaper;
};
KVMState *kvm_state;
@@ -389,6 +410,13 @@ static int do_kvm_destroy_vcpu(CPUState *cpu)
goto err;
}
+ if (cpu->kvm_dirty_gfns) {
+ ret = munmap(cpu->kvm_dirty_gfns, s->kvm_dirty_ring_size);
+ if (ret < 0) {
+ goto err;
+ }
+ }
+
vcpu = g_malloc0(sizeof(*vcpu));
vcpu->vcpu_id = kvm_arch_vcpu_id(cpu);
vcpu->kvm_fd = cpu->kvm_fd;
@@ -465,6 +493,19 @@ int kvm_init_vcpu(CPUState *cpu, Error **errp)
(void *)cpu->kvm_run + s->coalesced_mmio * PAGE_SIZE;
}
+ if (s->kvm_dirty_ring_size) {
+ /* Use MAP_SHARED to share pages with the kernel */
+ cpu->kvm_dirty_gfns = mmap(NULL, s->kvm_dirty_ring_size,
+ PROT_READ | PROT_WRITE, MAP_SHARED,
+ cpu->kvm_fd,
+ PAGE_SIZE * KVM_DIRTY_LOG_PAGE_OFFSET);
+ if (cpu->kvm_dirty_gfns == MAP_FAILED) {
+ ret = -errno;
+ DPRINTF("mmap'ing vcpu dirty gfns failed: %d\n", ret);
+ goto err;
+ }
+ }
+
ret = kvm_arch_init_vcpu(cpu);
if (ret < 0) {
error_setg_errno(errp, -ret,
@@ -583,6 +624,11 @@ static void kvm_slot_sync_dirty_pages(KVMSlot *slot)
cpu_physical_memory_set_dirty_lebitmap(slot->dirty_bmap, start, pages);
}
+static void kvm_slot_reset_dirty_pages(KVMSlot *slot)
+{
+ memset(slot->dirty_bmap, 0, slot->dirty_bmap_size);
+}
+
#define ALIGN(x, y) (((x)+(y)-1) & ~((y)-1))
/* Allocate the dirty bitmap for a slot */
@@ -639,6 +685,171 @@ static bool kvm_slot_get_dirty_log(KVMState *s, KVMSlot *slot)
return ret == 0;
}
+/* Should be with all slots_lock held for the address spaces. */
+static void kvm_dirty_ring_mark_page(KVMState *s, uint32_t as_id,
+ uint32_t slot_id, uint64_t offset)
+{
+ KVMMemoryListener *kml;
+ KVMSlot *mem;
+
+ if (as_id >= s->nr_as) {
+ return;
+ }
+
+ kml = s->as[as_id].ml;
+ mem = &kml->slots[slot_id];
+
+ if (!mem->memory_size || offset >=
+ (mem->memory_size / qemu_real_host_page_size)) {
+ return;
+ }
+
+ set_bit(offset, mem->dirty_bmap);
+}
+
+static bool dirty_gfn_is_dirtied(struct kvm_dirty_gfn *gfn)
+{
+ return gfn->flags == KVM_DIRTY_GFN_F_DIRTY;
+}
+
+static void dirty_gfn_set_collected(struct kvm_dirty_gfn *gfn)
+{
+ gfn->flags = KVM_DIRTY_GFN_F_RESET;
+}
+
+/*
+ * Should be with all slots_lock held for the address spaces. It returns the
+ * dirty page we've collected on this dirty ring.
+ */
+static uint32_t kvm_dirty_ring_reap_one(KVMState *s, CPUState *cpu)
+{
+ struct kvm_dirty_gfn *dirty_gfns = cpu->kvm_dirty_gfns, *cur;
+ uint32_t ring_size = s->kvm_dirty_ring_size;
+ uint32_t count = 0, fetch = cpu->kvm_fetch_index;
+
+ assert(dirty_gfns && ring_size);
+ trace_kvm_dirty_ring_reap_vcpu(cpu->cpu_index);
+
+ while (true) {
+ cur = &dirty_gfns[fetch % ring_size];
+ if (!dirty_gfn_is_dirtied(cur)) {
+ break;
+ }
+ kvm_dirty_ring_mark_page(s, cur->slot >> 16, cur->slot & 0xffff,
+ cur->offset);
+ dirty_gfn_set_collected(cur);
+ trace_kvm_dirty_ring_page(cpu->cpu_index, fetch, cur->offset);
+ fetch++;
+ count++;
+ }
+ cpu->kvm_fetch_index = fetch;
+
+ return count;
+}
+
+/* Must be with slots_lock held */
+static uint64_t kvm_dirty_ring_reap_locked(KVMState *s)
+{
+ int ret;
+ CPUState *cpu;
+ uint64_t total = 0;
+ int64_t stamp;
+
+ stamp = get_clock();
+
+ CPU_FOREACH(cpu) {
+ total += kvm_dirty_ring_reap_one(s, cpu);
+ }
+
+ if (total) {
+ ret = kvm_vm_ioctl(s, KVM_RESET_DIRTY_RINGS);
+ assert(ret == total);
+ }
+
+ stamp = get_clock() - stamp;
+
+ if (total) {
+ trace_kvm_dirty_ring_reap(total, stamp / 1000);
+ }
+
+ return total;
+}
+
+/*
+ * Currently for simplicity, we must hold BQL before calling this. We can
+ * consider to drop the BQL if we're clear with all the race conditions.
+ */
+static uint64_t kvm_dirty_ring_reap(KVMState *s)
+{
+ uint64_t total;
+
+ /*
+ * We need to lock all kvm slots for all address spaces here,
+ * because:
+ *
+ * (1) We need to mark dirty for dirty bitmaps in multiple slots
+ * and for tons of pages, so it's better to take the lock here
+ * once rather than once per page. And more importantly,
+ *
+ * (2) We must _NOT_ publish dirty bits to the other threads
+ * (e.g., the migration thread) via the kvm memory slot dirty
+ * bitmaps before correctly re-protect those dirtied pages.
+ * Otherwise we can have potential risk of data corruption if
+ * the page data is read in the other thread before we do
+ * reset below.
+ */
+ kvm_slots_lock();
+ total = kvm_dirty_ring_reap_locked(s);
+ kvm_slots_unlock();
+
+ return total;
+}
+
+static void do_kvm_cpu_synchronize_kick(CPUState *cpu, run_on_cpu_data arg)
+{
+ /* No need to do anything */
+}
+
+/*
+ * Kick all vcpus out in a synchronized way. When returned, we
+ * guarantee that every vcpu has been kicked and at least returned to
+ * userspace once.
+ */
+static void kvm_cpu_synchronize_kick_all(void)
+{
+ CPUState *cpu;
+
+ CPU_FOREACH(cpu) {
+ run_on_cpu(cpu, do_kvm_cpu_synchronize_kick, RUN_ON_CPU_NULL);
+ }
+}
+
+/*
+ * Flush all the existing dirty pages to the KVM slot buffers. When
+ * this call returns, we guarantee that all the touched dirty pages
+ * before calling this function have been put into the per-kvmslot
+ * dirty bitmap.
+ *
+ * This function must be called with BQL held.
+ */
+static void kvm_dirty_ring_flush(void)
+{
+ trace_kvm_dirty_ring_flush(0);
+ /*
+ * The function needs to be serialized. Since this function
+ * should always be with BQL held, serialization is guaranteed.
+ * However, let's be sure of it.
+ */
+ assert(qemu_mutex_iothread_locked());
+ /*
+ * First make sure to flush the hardware buffers by kicking all
+ * vcpus out in a synchronous way.
+ */
+ kvm_cpu_synchronize_kick_all();
+ kvm_dirty_ring_reap(kvm_state);
+ trace_kvm_dirty_ring_flush(1);
+}
+
/**
* kvm_physical_sync_dirty_bitmap - Sync dirty bitmap from kernel space
*
@@ -1164,7 +1375,24 @@ static void kvm_set_phys_mem(KVMMemoryListener *kml,
goto out;
}
if (mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
- kvm_slot_get_dirty_log(kvm_state, mem);
+ /*
+ * NOTE: We should be aware of the fact that here we're only
+ * doing a best effort to sync dirty bits. No matter whether
+ * we're using dirty log or dirty ring, we ignored two facts:
+ *
+ * (1) dirty bits can reside in hardware buffers (PML)
+ *
+ * (2) after we collected dirty bits here, pages can be dirtied
+ * again before we do the final KVM_SET_USER_MEMORY_REGION to
+ * remove the slot.
+ *
+ * Not easy. Let's cross the fingers until it's fixed.
+ */
+ if (kvm_state->kvm_dirty_ring_size) {
+ kvm_dirty_ring_reap_locked(kvm_state);
+ } else {
+ kvm_slot_get_dirty_log(kvm_state, mem);
+ }
kvm_slot_sync_dirty_pages(mem);
}
@@ -1212,6 +1440,51 @@ out:
kvm_slots_unlock();
}
+static void *kvm_dirty_ring_reaper_thread(void *data)
+{
+ KVMState *s = data;
+ struct KVMDirtyRingReaper *r = &s->reaper;
+
+ rcu_register_thread();
+
+ trace_kvm_dirty_ring_reaper("init");
+
+ while (true) {
+ r->reaper_state = KVM_DIRTY_RING_REAPER_WAIT;
+ trace_kvm_dirty_ring_reaper("wait");
+ /*
+ * TODO: provide a smarter timeout rather than a constant?
+ */
+ sleep(1);
+
+ trace_kvm_dirty_ring_reaper("wakeup");
+ r->reaper_state = KVM_DIRTY_RING_REAPER_REAPING;
+
+ qemu_mutex_lock_iothread();
+ kvm_dirty_ring_reap(s);
+ qemu_mutex_unlock_iothread();
+
+ r->reaper_iteration++;
+ }
+
+ trace_kvm_dirty_ring_reaper("exit");
+
+ rcu_unregister_thread();
+
+ return NULL;
+}
+
+static int kvm_dirty_ring_reaper_init(KVMState *s)
+{
+ struct KVMDirtyRingReaper *r = &s->reaper;
+
+ qemu_thread_create(&r->reaper_thr, "kvm-reaper",
+ kvm_dirty_ring_reaper_thread,
+ s, QEMU_THREAD_JOINABLE);
+
+ return 0;
+}
+
static void kvm_region_add(MemoryListener *listener,
MemoryRegionSection *section)
{
@@ -1240,6 +1513,36 @@ static void kvm_log_sync(MemoryListener *listener,
kvm_slots_unlock();
}
+static void kvm_log_sync_global(MemoryListener *l)
+{
+ KVMMemoryListener *kml = container_of(l, KVMMemoryListener, listener);
+ KVMState *s = kvm_state;
+ KVMSlot *mem;
+ int i;
+
+ /* Flush all kernel dirty addresses into KVMSlot dirty bitmap */
+ kvm_dirty_ring_flush();
+
+ /*
+ * TODO: make this faster when nr_slots is big while there are
+ * only a few used slots (small VMs).
+ */
+ kvm_slots_lock();
+ for (i = 0; i < s->nr_slots; i++) {
+ mem = &kml->slots[i];
+ if (mem->memory_size && mem->flags & KVM_MEM_LOG_DIRTY_PAGES) {
+ kvm_slot_sync_dirty_pages(mem);
+ /*
+ * This is not needed by KVM_GET_DIRTY_LOG because the
+ * ioctl will unconditionally overwrite the whole region.
+ * However kvm dirty ring has no such side effect.
+ */
+ kvm_slot_reset_dirty_pages(mem);
+ }
+ }
+ kvm_slots_unlock();
+}
+
static void kvm_log_clear(MemoryListener *listener,
MemoryRegionSection *section)
{
@@ -1345,10 +1648,15 @@ void kvm_memory_listener_register(KVMState *s, KVMMemoryListener *kml,
kml->listener.region_del = kvm_region_del;
kml->listener.log_start = kvm_log_start;
kml->listener.log_stop = kvm_log_stop;
- kml->listener.log_sync = kvm_log_sync;
- kml->listener.log_clear = kvm_log_clear;
kml->listener.priority = 10;
+ if (s->kvm_dirty_ring_size) {
+ kml->listener.log_sync_global = kvm_log_sync_global;
+ } else {
+ kml->listener.log_sync = kvm_log_sync;
+ kml->listener.log_clear = kvm_log_clear;
+ }
+
memory_listener_register(&kml->listener, as);
for (i = 0; i < s->nr_as; ++i) {
@@ -2131,12 +2439,53 @@ static int kvm_init(MachineState *ms)
s->coalesced_pio = s->coalesced_mmio &&
kvm_check_extension(s, KVM_CAP_COALESCED_PIO);
+ /*
+ * Enable KVM dirty ring if supported, otherwise fall back to
+ * dirty logging mode
+ */
+ if (s->kvm_dirty_ring_size > 0) {
+ uint64_t ring_bytes;
+
+ ring_bytes = s->kvm_dirty_ring_size * sizeof(struct kvm_dirty_gfn);
+
+ /* Read the max supported pages */
+ ret = kvm_vm_check_extension(s, KVM_CAP_DIRTY_LOG_RING);
+ if (ret > 0) {
+ if (ring_bytes > ret) {
+ error_report("KVM dirty ring size %" PRIu32 " too big "
+ "(maximum is %ld). Please use a smaller value.",
+ s->kvm_dirty_ring_size,
+ (long)ret / sizeof(struct kvm_dirty_gfn));
+ ret = -EINVAL;
+ goto err;
+ }
+
+ ret = kvm_vm_enable_cap(s, KVM_CAP_DIRTY_LOG_RING, 0, ring_bytes);
+ if (ret) {
+ error_report("Enabling of KVM dirty ring failed: %s. "
+ "Suggested mininum value is 1024.", strerror(-ret));
+ goto err;
+ }
+
+ s->kvm_dirty_ring_bytes = ring_bytes;
+ } else {
+ warn_report("KVM dirty ring not available, using bitmap method");
+ s->kvm_dirty_ring_size = 0;
+ }
+ }
+
/*
* KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 is not needed when dirty ring is
* enabled. More importantly, KVM_DIRTY_LOG_INITIALLY_SET will assume no
* page is wr-protected initially, which is against how kvm dirty ring is
* usage - kvm dirty ring requires all pages are wr-protected at the very
* beginning. Enabling this feature for dirty ring causes data corruption.
+ *
+ * TODO: Without KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 and kvm clear dirty log,
+ * we may expect a higher stall time when starting the migration. In the
+ * future we can enable KVM_CLEAR_DIRTY_LOG to work with dirty ring too:
+ * instead of clearing dirty bit, it can be a way to explicitly wr-protect
+ * guest pages.
*/
if (!s->kvm_dirty_ring_size) {
dirty_log_manual_caps =
@@ -2239,6 +2588,14 @@ static int kvm_init(MachineState *ms)
ret = ram_block_discard_disable(true);
assert(!ret);
}
+
+ if (s->kvm_dirty_ring_size) {
+ ret = kvm_dirty_ring_reaper_init(s);
+ if (ret) {
+ goto err;
+ }
+ }
+
return 0;
err:
@@ -2551,6 +2908,17 @@ int kvm_cpu_exec(CPUState *cpu)
case KVM_EXIT_INTERNAL_ERROR:
ret = kvm_handle_internal_error(cpu, run);
break;
+ case KVM_EXIT_DIRTY_RING_FULL:
+ /*
+ * We shouldn't continue if the dirty ring of this vcpu is
+ * still full. Got kicked by KVM_RESET_DIRTY_RINGS.
+ */
+ trace_kvm_dirty_ring_full(cpu->cpu_index);
+ qemu_mutex_lock_iothread();
+ kvm_dirty_ring_reap(kvm_state);
+ qemu_mutex_unlock_iothread();
+ ret = 0;
+ break;
case KVM_EXIT_SYSTEM_EVENT:
switch (run->system_event.type) {
case KVM_SYSTEM_EVENT_SHUTDOWN:
@@ -18,4 +18,11 @@ kvm_set_ioeventfd_pio(int fd, uint16_t addr, uint32_t val, bool assign, uint32_t
kvm_set_user_memory(uint32_t slot, uint32_t flags, uint64_t guest_phys_addr, uint64_t memory_size, uint64_t userspace_addr, int ret) "Slot#%d flags=0x%x gpa=0x%"PRIx64 " size=0x%"PRIx64 " ua=0x%"PRIx64 " ret=%d"
kvm_clear_dirty_log(uint32_t slot, uint64_t start, uint32_t size) "slot#%"PRId32" start 0x%"PRIx64" size 0x%"PRIx32
kvm_resample_fd_notify(int gsi) "gsi %d"
+kvm_dirty_ring_full(int id) "vcpu %d"
+kvm_dirty_ring_reap_vcpu(int id) "vcpu %d"
+kvm_dirty_ring_page(int vcpu, uint32_t slot, uint64_t offset) "vcpu %d fetch %"PRIu32" offset 0x%"PRIx64
+kvm_dirty_ring_reaper(const char *s) "%s"
+kvm_dirty_ring_reap(uint64_t count, int64_t t) "reaped %"PRIu64" pages (took %"PRIi64" us)"
+kvm_dirty_ring_reaper_kick(const char *reason) "%s"
+kvm_dirty_ring_flush(int finished) "%d"
@@ -329,6 +329,10 @@ struct qemu_work_item;
* @ignore_memory_transaction_failures: Cached copy of the MachineState
* flag of the same name: allows the board to suppress calling of the
* CPU do_transaction_failed hook function.
+ * @kvm_dirty_gfns: Points to the KVM dirty ring for this CPU when KVM dirty
+ * ring is enabled.
+ * @kvm_fetch_index: Keeps the index that we last fetched from the per-vCPU
+ * dirty ring structure.
*
* State of one CPU core or thread.
*/
@@ -400,9 +404,12 @@ struct CPUState {
*/
uintptr_t mem_io_pc;
+ /* Only used in KVM */
int kvm_fd;
struct KVMState *kvm_state;
struct kvm_run *kvm_run;
+ struct kvm_dirty_gfn *kvm_dirty_gfns;
+ uint32_t kvm_fetch_index;
/* Used for events with 'vcpu' and *without* the 'disabled' properties */
DECLARE_BITMAP(trace_dstate_delayed, CPU_TRACE_DSTATE_MAX_EVENTS);