From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
The PMI holds the state of each page on the incoming side,
so that we can tell if the page is missing, already received
or there is a request outstanding for it.
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
---
include/migration/migration.h | 19 ++++
include/migration/postcopy-ram.h | 12 +++
include/qemu/typedefs.h | 1 +
postcopy-ram.c | 220 +++++++++++++++++++++++++++++++++++++++
4 files changed, 252 insertions(+)
diff --git a/include/migration/migration.h b/include/migration/migration.h
index 2ff9d35..1405a15 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -57,6 +57,24 @@ struct MigrationRetPathState {
typedef struct MigrationState MigrationState;
+/* Postcopy page-map-incoming - data about each page on the inbound side */
+
+typedef enum {
+ POSTCOPY_PMI_MISSING, /* page hasn't yet been received */
+ POSTCOPY_PMI_REQUESTED, /* Kernel asked for a page, but we've not got it */
+ POSTCOPY_PMI_RECEIVED /* We've got the page */
+} PostcopyPMIState;
+
+struct PostcopyPMI {
+ QemuMutex mutex;
+ unsigned long *received_map; /* Pages that we have received */
+ unsigned long *requested_map; /* Pages that we're sending a request for */
+ unsigned long host_mask; /* A mask with enough bits set to cover one
+ host page in the PMI */
+ unsigned long host_bits; /* The number of bits in the map representing
+ one host page */
+};
+
/* State for the incoming migration */
struct MigrationIncomingState {
QEMUFile *file;
@@ -71,6 +89,7 @@ struct MigrationIncomingState {
QEMUFile *return_path;
QemuMutex rp_mutex; /* We send replies from multiple threads */
+ PostcopyPMI postcopy_pmi;
};
MigrationIncomingState *migration_incoming_get_current(void);
diff --git a/include/migration/postcopy-ram.h b/include/migration/postcopy-ram.h
index dcd1afa..addb88a 100644
--- a/include/migration/postcopy-ram.h
+++ b/include/migration/postcopy-ram.h
@@ -13,7 +13,19 @@
#ifndef QEMU_POSTCOPY_RAM_H
#define QEMU_POSTCOPY_RAM_H
+#include "migration/migration.h"
+
/* Return 0 if the host supports everything we need to do postcopy-ram */
int postcopy_ram_hosttest(void);
+/*
+ * In 'advise' mode record that a page has been received.
+ */
+void postcopy_hook_early_receive(MigrationIncomingState *mis,
+ size_t bitmap_index);
+
+void postcopy_pmi_destroy(MigrationIncomingState *mis);
+void postcopy_pmi_discard_range(MigrationIncomingState *mis,
+ size_t start, size_t npages);
+void postcopy_pmi_dump(MigrationIncomingState *mis);
#endif
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index 8539de6..61b330c 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -77,6 +77,7 @@ typedef struct QEMUSGList QEMUSGList;
typedef struct SHPCDevice SHPCDevice;
typedef struct FWCfgState FWCfgState;
typedef struct PcGuestInfo PcGuestInfo;
+typedef struct PostcopyPMI PostcopyPMI;
typedef struct Range Range;
typedef struct AdapterInfo AdapterInfo;
diff --git a/postcopy-ram.c b/postcopy-ram.c
index bba5c71..210585c 100644
--- a/postcopy-ram.c
+++ b/postcopy-ram.c
@@ -23,6 +23,9 @@
#include "qemu-common.h"
#include "migration/migration.h"
#include "migration/postcopy-ram.h"
+#include "sysemu/sysemu.h"
+#include "qemu/bitmap.h"
+#include "qemu/error-report.h"
//#define DEBUG_POSTCOPY
@@ -82,6 +85,216 @@
#if defined(__linux__) && defined(MADV_USERFAULT) && \
defined(__NR_remap_anon_pages)
+/* ---------------------------------------------------------------------- */
+/* Postcopy pagemap-inbound (pmi) - data structures that record the */
+/* state of each page used by the inbound postcopy */
+/* It's a pair of bitmaps (of the same structure as the migration bitmaps)*/
+/* holding one bit per target-page, although all operations work on host */
+/* pages. */
+__attribute__ (( unused )) /* Until later in patch series */
+static void postcopy_pmi_init(MigrationIncomingState *mis, size_t ram_pages)
+{
+ unsigned int tpb = qemu_target_page_bits();
+ unsigned long host_bits;
+
+ qemu_mutex_init(&mis->postcopy_pmi.mutex);
+ mis->postcopy_pmi.received_map = bitmap_new(ram_pages);
+ mis->postcopy_pmi.requested_map = bitmap_new(ram_pages);
+ bitmap_clear(mis->postcopy_pmi.received_map, 0, ram_pages);
+ bitmap_clear(mis->postcopy_pmi.requested_map, 0, ram_pages);
+ /*
+ * Each bit in the map represents one 'target page' which is no bigger
+ * than a host page but can be smaller. It's useful to have some
+ * convenience masks for later
+ */
+
+ /*
+ * The number of bits one host page takes up in the bitmap
+ * e.g. on a 64k host page, 4k Target page, host_bits=64/4=16
+ */
+ host_bits = sysconf(_SC_PAGESIZE) / (1ul << tpb);
+ /* Should be a power of 2 */
+ assert(host_bits && !(host_bits & (host_bits - 1)));
+ /*
+ * If the host_bits isn't a division of the number of bits in long
+ * then the code gets a lot more complex; disallow for now
+ * (I'm not aware of a system where it's true anyway)
+ */
+ assert(((sizeof(long) * 8) % host_bits) == 0);
+
+ mis->postcopy_pmi.host_bits = host_bits;
+ /* A mask, starting at bit 0, containing host_bits continuous set bits */
+ mis->postcopy_pmi.host_mask = (1ul << host_bits) - 1;
+
+ assert((ram_pages % host_bits) == 0);
+}
+
+void postcopy_pmi_destroy(MigrationIncomingState *mis)
+{
+ if (mis->postcopy_pmi.received_map) {
+ g_free(mis->postcopy_pmi.received_map);
+ mis->postcopy_pmi.received_map = NULL;
+ }
+ if (mis->postcopy_pmi.requested_map) {
+ g_free(mis->postcopy_pmi.requested_map);
+ mis->postcopy_pmi.requested_map = NULL;
+ }
+ qemu_mutex_destroy(&mis->postcopy_pmi.mutex);
+}
+
+/*
+ * Mark a set of pages in the PMI as being clear; this is used by the discard
+ * at the start of postcopy, and before the postcopy stream starts.
+ */
+void postcopy_pmi_discard_range(MigrationIncomingState *mis,
+ size_t start, size_t npages)
+{
+ bitmap_clear(mis->postcopy_pmi.received_map, start, npages);
+}
+
+/*
+ * Test a host-page worth of bits in the map starting at bitmap_index
+ * The bits should all be consistent
+ */
+static bool test_hpbits(MigrationIncomingState *mis,
+ size_t bitmap_index, unsigned long *map)
+{
+ long masked;
+
+ assert((bitmap_index & (mis->postcopy_pmi.host_bits-1)) == 0);
+
+ masked = (map[BIT_WORD(bitmap_index)] >>
+ (bitmap_index % BITS_PER_LONG)) &
+ mis->postcopy_pmi.host_mask;
+
+ assert((masked == 0) || (masked == mis->postcopy_pmi.host_mask));
+ return !!masked;
+}
+
+/*
+ * Set host-page worth of bits in the map starting at bitmap_index
+ */
+static void set_hpbits(MigrationIncomingState *mis,
+ size_t bitmap_index, unsigned long *map)
+{
+ assert((bitmap_index & (mis->postcopy_pmi.host_bits-1)) == 0);
+
+ map[BIT_WORD(bitmap_index)] |= mis->postcopy_pmi.host_mask <<
+ (bitmap_index % BITS_PER_LONG);
+}
+
+/*
+ * Clear host-page worth of bits in the map starting at bitmap_index
+ */
+static void clear_hpbits(MigrationIncomingState *mis,
+ size_t bitmap_index, unsigned long *map)
+{
+ assert((bitmap_index & (mis->postcopy_pmi.host_bits-1)) == 0);
+
+ map[BIT_WORD(bitmap_index)] &= ~(mis->postcopy_pmi.host_mask <<
+ (bitmap_index % BITS_PER_LONG));
+}
+
+/*
+ * Retrieve the state of the given page
+ * Note: This version for use by callers already holding the lock
+ */
+static PostcopyPMIState postcopy_pmi_get_state_nolock(
+ MigrationIncomingState *mis,
+ size_t bitmap_index)
+{
+ bool received, requested;
+
+ received = test_hpbits(mis, bitmap_index, mis->postcopy_pmi.received_map);
+ requested = test_hpbits(mis, bitmap_index,
mis->postcopy_pmi.requested_map);
+
+ if (received) {
+ assert(!requested);
+ return POSTCOPY_PMI_RECEIVED;
+ } else {
+ return requested ? POSTCOPY_PMI_REQUESTED : POSTCOPY_PMI_MISSING;
+ }
+}
+
+/* Retrieve the state of the given page */
+__attribute__ (( unused )) /* Until later in patch series */
+static PostcopyPMIState postcopy_pmi_get_state(MigrationIncomingState *mis,
+ size_t bitmap_index)
+{
+ PostcopyPMIState ret;
+ qemu_mutex_lock(&mis->postcopy_pmi.mutex);
+ ret = postcopy_pmi_get_state_nolock(mis, bitmap_index);
+ qemu_mutex_unlock(&mis->postcopy_pmi.mutex);
+
+ return ret;
+}
+
+/*
+ * Set the page state to the given state if the previous state was as expected
+ * Return the actual previous state.
+ */
+__attribute__ (( unused )) /* Until later in patch series */
+static PostcopyPMIState postcopy_pmi_change_state(MigrationIncomingState *mis,
+ size_t bitmap_index,
+ PostcopyPMIState expected_state,
+ PostcopyPMIState new_state)
+{
+ PostcopyPMIState old_state;
+
+ qemu_mutex_lock(&mis->postcopy_pmi.mutex);
+ old_state = postcopy_pmi_get_state_nolock(mis, bitmap_index);
+
+ if (old_state == expected_state) {
+ switch (new_state) {
+ case POSTCOPY_PMI_MISSING:
+ assert(0); /* This shouldn't actually happen - use discard_range */
+ break;
+
+ case POSTCOPY_PMI_REQUESTED:
+ assert(old_state == POSTCOPY_PMI_MISSING);
+ set_hpbits(mis, bitmap_index, mis->postcopy_pmi.requested_map);
+ break;
+
+ case POSTCOPY_PMI_RECEIVED:
+ assert(old_state == POSTCOPY_PMI_MISSING ||
+ old_state == POSTCOPY_PMI_REQUESTED);
+ set_hpbits(mis, bitmap_index, mis->postcopy_pmi.received_map);
+ clear_hpbits(mis, bitmap_index, mis->postcopy_pmi.requested_map);
+ break;
+ }
+ }
+
+ qemu_mutex_unlock(&mis->postcopy_pmi.mutex);
+ return old_state;
+}
+
+/*
+ * Useful when debugging postcopy, although if it failed early the
+ * received map can be quite sparse and thus big when dumped.
+ */
+void postcopy_pmi_dump(MigrationIncomingState *mis)
+{
+ fprintf(stderr, "postcopy_pmi_dump: requested\n");
+ ram_debug_dump_bitmap(mis->postcopy_pmi.requested_map, false);
+ fprintf(stderr, "postcopy_pmi_dump: received\n");
+ ram_debug_dump_bitmap(mis->postcopy_pmi.received_map, true);
+ fprintf(stderr, "postcopy_pmi_dump: end\n");
+}
+
+/* Called by ram_load prior to mapping the page */
+void postcopy_hook_early_receive(MigrationIncomingState *mis,
+ size_t bitmap_index)
+{
+ if (mis->postcopy_ram_state == POSTCOPY_RAM_INCOMING_ADVISE) {
+ /*
+ * If we're in precopy-advise mode we need to track received pages even
+ * though we don't need to place pages atomically yet.
+ * In advise mode there's only a single thread, so don't need locks
+ */
+ set_bit(bitmap_index, mis->postcopy_pmi.received_map);
+ }
+}
+
int postcopy_ram_hosttest(void)
{
/* TODO: Needs guarding with CONFIG_ once we have libc's that have the defs
@@ -156,5 +369,12 @@ int postcopy_ram_hosttest(void)
return -1;
}
+/* Called by ram_load prior to mapping the page */
+void postcopy_hook_early_receive(MigrationIncomingState *mis,
+ size_t bitmap_index)
+{
+ /* We don't support postcopy so don't care */
+}
+
#endif
--
1.9.3
