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[Qemu-devel] [PATCH v5 26/45] Postcopy page-map-incoming (PMI) structure
From: |
Dr. David Alan Gilbert (git) |
Subject: |
[Qemu-devel] [PATCH v5 26/45] Postcopy page-map-incoming (PMI) structure |
Date: |
Wed, 25 Feb 2015 16:51:49 +0000 |
From: "Dr. David Alan Gilbert" <address@hidden>
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 <address@hidden>
---
include/migration/migration.h | 18 ++++
include/migration/postcopy-ram.h | 12 +++
include/qemu/typedefs.h | 1 +
migration/postcopy-ram.c | 223 +++++++++++++++++++++++++++++++++++++++
4 files changed, 254 insertions(+)
diff --git a/include/migration/migration.h b/include/migration/migration.h
index b44b9b2..86200b9 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -48,6 +48,23 @@ enum mig_rpcomm_cmd {
MIG_RP_CMD_PONG, /* Response to a PING; data (seq: be32 ) */
};
+/* Postcopy page-map-incoming - data about each page on the inbound side */
+typedef enum {
+ POSTCOPY_PMI_MISSING = 0, /* page hasn't yet been received */
+ POSTCOPY_PMI_REQUESTED = 1, /* Kernel asked for a page, not yet got it */
+ POSTCOPY_PMI_RECEIVED = 2, /* We've got the page */
+} PostcopyPMIState;
+
+struct PostcopyPMI {
+ QemuMutex mutex;
+ unsigned long *state0; /* Together with state1 form a */
+ unsigned long *state1; /* PostcopyPMIState */
+ 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 */
+};
+
typedef QLIST_HEAD(, LoadStateEntry) LoadStateEntry_Head;
typedef enum {
@@ -69,6 +86,7 @@ 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 d81934f..e93ee8a 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 true if the host supports everything we need to do postcopy-ram */
bool postcopy_ram_supported_by_host(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 611db46..924eeb6 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -61,6 +61,7 @@ typedef struct PCIExpressHost PCIExpressHost;
typedef struct PCIHostState PCIHostState;
typedef struct PCMCIACardState PCMCIACardState;
typedef struct PixelFormat PixelFormat;
+typedef struct PostcopyPMI PostcopyPMI;
typedef struct PropertyInfo PropertyInfo;
typedef struct Property Property;
typedef struct QEMUBH QEMUBH;
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index a0e20b2..4f29055 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -24,6 +24,7 @@
#include "migration/migration.h"
#include "migration/postcopy-ram.h"
#include "sysemu/sysemu.h"
+#include "qemu/bitmap.h"
#include "qemu/error-report.h"
#include "trace.h"
@@ -49,6 +50,220 @@
#if defined(__linux__) && defined(__NR_userfaultfd)
+/* ---------------------------------------------------------------------- */
+/* 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 most operations work on host */
+/* pages, the exception being a hook that receives incoming pages off the */
+/* migration stream which come in a TP at a time, although the source */
+/* _should_ guarantee it sends a sequence of TPs representing HPs during */
+/* the postcopy phase, there is no such guarantee during precopy. We */
+/* could boil this down to only holding one bit per-host page, but we lose*/
+/* sanity checking that we really do get whole host-pages from the source.*/
+__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.state0 = bitmap_new(ram_pages);
+ mis->postcopy_pmi.state1 = bitmap_new(ram_pages);
+ bitmap_clear(mis->postcopy_pmi.state0, 0, ram_pages);
+ bitmap_clear(mis->postcopy_pmi.state1, 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 = getpagesize() / (1ul << tpb);
+ assert(is_power_of_2(host_bits));
+
+ mis->postcopy_pmi.host_bits = host_bits;
+
+ if (host_bits < BITS_PER_LONG) {
+ /* A mask starting at bit 0 containing host_bits continuous set bits */
+ mis->postcopy_pmi.host_mask = (1ul << host_bits) - 1;
+ } else {
+ /*
+ * This is a host where the ratio between host and target pages is
+ * bigger than the size of our longs, so we can't make a mask
+ * but we are only losing sanity checking if we just check one long's
+ * worth of bits.
+ */
+ mis->postcopy_pmi.host_mask = ~0l;
+ }
+
+
+ assert((ram_pages % host_bits) == 0);
+}
+
+void postcopy_pmi_destroy(MigrationIncomingState *mis)
+{
+ g_free(mis->postcopy_pmi.state0);
+ mis->postcopy_pmi.state0 = NULL;
+ g_free(mis->postcopy_pmi.state1);
+ mis->postcopy_pmi.state1 = 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)
+{
+ /* Clear to state 0 = missing */
+ bitmap_clear(mis->postcopy_pmi.state0, start, npages);
+ bitmap_clear(mis->postcopy_pmi.state1, 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
+ * to the given state
+ */
+static void set_hp(MigrationIncomingState *mis,
+ size_t bitmap_index, PostcopyPMIState state)
+{
+ long shifted_mask = mis->postcopy_pmi.host_mask <<
+ (bitmap_index % BITS_PER_LONG);
+
+ assert((bitmap_index & (mis->postcopy_pmi.host_bits-1)) == 0);
+
+ if (state & 1) {
+ mis->postcopy_pmi.state0[BIT_WORD(bitmap_index)] |= shifted_mask;
+ } else {
+ mis->postcopy_pmi.state0[BIT_WORD(bitmap_index)] &= ~shifted_mask;
+ }
+ if (state & 2) {
+ mis->postcopy_pmi.state1[BIT_WORD(bitmap_index)] |= shifted_mask;
+ } else {
+ mis->postcopy_pmi.state1[BIT_WORD(bitmap_index)] &= ~shifted_mask;
+ }
+}
+
+/*
+ * 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 b0, b1;
+
+ b0 = test_hpbits(mis, bitmap_index, mis->postcopy_pmi.state0);
+ b1 = test_hpbits(mis, bitmap_index, mis->postcopy_pmi.state1);
+
+ return (b0 ? 1 : 0) + (b1 ? 2 : 0);
+}
+
+/* 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 happen - use discard_range */
+ break;
+
+ case POSTCOPY_PMI_REQUESTED:
+ assert(old_state == POSTCOPY_PMI_MISSING);
+ /* missing -> requested */
+ set_hp(mis, bitmap_index, POSTCOPY_PMI_REQUESTED);
+ break;
+
+ case POSTCOPY_PMI_RECEIVED:
+ assert(old_state == POSTCOPY_PMI_MISSING ||
+ old_state == POSTCOPY_PMI_REQUESTED);
+ /* -> received */
+ set_hp(mis, bitmap_index, POSTCOPY_PMI_RECEIVED);
+ 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: bit 0\n");
+ ram_debug_dump_bitmap(mis->postcopy_pmi.state0, false);
+ fprintf(stderr, "postcopy_pmi_dump: bit 1\n");
+ ram_debug_dump_bitmap(mis->postcopy_pmi.state1, 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_state == POSTCOPY_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.state1); /* 2=received */
+ }
+}
+
static bool ufd_version_check(int ufd)
{
struct uffdio_api api_struct;
@@ -71,6 +286,7 @@ static bool ufd_version_check(int ufd)
return true;
}
+
bool postcopy_ram_supported_by_host(void)
{
long pagesize = getpagesize();
@@ -157,5 +373,12 @@ bool postcopy_ram_supported_by_host(void)
return false;
}
+/* 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
--
2.1.0
- [Qemu-devel] [PATCH v5 19/45] migrate_init: Call from savevm, (continued)
- [Qemu-devel] [PATCH v5 19/45] migrate_init: Call from savevm, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 18/45] MIG_CMD_PACKAGED: Send a packaged chunk of migration stream, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 16/45] Add migration-capability boolean for postcopy-ram., Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 17/45] Add wrappers and handlers for sending/receiving the postcopy-ram migration messages., Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 21/45] Add Linux userfaultfd header, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 20/45] Modify savevm handlers for postcopy, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 24/45] MIG_STATE_POSTCOPY_ACTIVE: Add new migration state, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 22/45] postcopy: OS support test, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 25/45] qemu_savevm_state_complete: Postcopy changes, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 26/45] Postcopy page-map-incoming (PMI) structure,
Dr. David Alan Gilbert (git) <=
- [Qemu-devel] [PATCH v5 29/45] postcopy: ram_enable_notify to switch on userfault, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 28/45] postcopy: Incoming initialisation, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 27/45] Postcopy: Maintain sentmap and calculate discard, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 30/45] Postcopy: Postcopy startup in migration thread, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 31/45] Postcopy end in migration_thread, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 32/45] Page request: Add MIG_RP_CMD_REQ_PAGES reverse command, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 33/45] Page request: Process incoming page request, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 34/45] Page request: Consume pages off the post-copy queue, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 35/45] postcopy_ram.c: place_page and helpers, Dr. David Alan Gilbert (git), 2015/02/25
- [Qemu-devel] [PATCH v5 36/45] Postcopy: Use helpers to map pages during migration, Dr. David Alan Gilbert (git), 2015/02/25