[Qemu-devel] [PATCH v6 35/47] Page request: Process incoming page request

["Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>]

From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>

On receiving MIG_RPCOMM_REQ_PAGES look up the address and
queue the page.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
---
 arch_init.c                   | 64 ++++++++++++++++++++++++++++++++++++++++++-
 include/exec/cpu-all.h        |  2 --
 include/migration/migration.h | 21 ++++++++++++++
 include/qemu/typedefs.h       |  1 +
 migration/migration.c         | 31 +++++++++++++++++++++
 trace-events                  |  1 +
 6 files changed, 117 insertions(+), 3 deletions(-)

diff --git a/arch_init.c b/arch_init.c
index 2c937d1..48403f3 100644
--- a/arch_init.c
+++ b/arch_init.c
@@ -715,7 +715,69 @@ static int ram_save_page(QEMUFile *f, RAMBlock* block, ram_addr_t offset,
     return pages;
 }
 
-/**
+/*
+ * Queue the pages for transmission, e.g. a request from postcopy destination
+ *   ms: MigrationStatus in which the queue is held
+ *   rbname: The RAMBlock the request is for - may be NULL (to mean reuse last)
+ *   start: Offset from the start of the RAMBlock
+ *   len: Length (in bytes) to send
+ *   Return: 0 on success
+ */
+int ram_save_queue_pages(MigrationState *ms, const char *rbname,
+                         ram_addr_t start, ram_addr_t len)
+{
+    RAMBlock *ramblock;
+
+    rcu_read_lock();
+    if (!rbname) {
+        /* Reuse last RAMBlock */
+        ramblock = ms->last_req_rb;
+
+        if (!ramblock) {
+            /*
+             * Shouldn't happen, we can't reuse the last RAMBlock if
+             * it's the 1st request.
+             */
+            error_report("ram_save_queue_pages no previous block");
+            goto err;
+        }
+    } else {
+        ramblock = ram_find_block(rbname);
+
+        if (!ramblock) {
+            /* We shouldn't be asked for a non-existent RAMBlock */
+            error_report("ram_save_queue_pages no block '%s'", rbname);
+            goto err;
+        }
+    }
+    trace_ram_save_queue_pages(ramblock->idstr, start, len);
+    if (start+len > ramblock->used_length) {
+        error_report("%s request overrun start=%zx len=%zx blocklen=%zx",
+                     __func__, start, len, ramblock->used_length);
+        goto err;
+    }
+
+    struct MigrationSrcPageRequest *new_entry =
+        g_malloc0(sizeof(struct MigrationSrcPageRequest));
+    new_entry->rb = ramblock;
+    new_entry->offset = start;
+    new_entry->len = len;
+    ms->last_req_rb = ramblock;
+
+    qemu_mutex_lock(&ms->src_page_req_mutex);
+    memory_region_ref(ramblock->mr);
+    QSIMPLEQ_INSERT_TAIL(&ms->src_page_requests, new_entry, next_req);
+    qemu_mutex_unlock(&ms->src_page_req_mutex);
+    rcu_read_unlock();
+
+    return 0;
+
+err:
+    rcu_read_unlock();
+    return -1;
+}
+
+/*
  * ram_find_and_save_block: Finds a dirty page and sends it to f
  *
  * Called within an RCU critical section.
diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h
index ac06c67..1f336e6 100644
--- a/include/exec/cpu-all.h
+++ b/include/exec/cpu-all.h
@@ -266,8 +266,6 @@ CPUArchState *cpu_copy(CPUArchState *env);
 
 /* memory API */
 
-typedef struct RAMBlock RAMBlock;
-
 struct RAMBlock {
     struct rcu_head rcu;
     struct MemoryRegion *mr;
diff --git a/include/migration/migration.h b/include/migration/migration.h
index 37bd54a..75c3299 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -88,6 +88,18 @@ MigrationIncomingState *migration_incoming_get_current(void);
 MigrationIncomingState *migration_incoming_state_new(QEMUFile *f);
 void migration_incoming_state_destroy(void);
 
+/*
+ * An outstanding page request, on the source, having been received
+ * and queued
+ */
+struct MigrationSrcPageRequest {
+    RAMBlock *rb;
+    hwaddr    offset;
+    hwaddr    len;
+
+    QSIMPLEQ_ENTRY(MigrationSrcPageRequest) next_req;
+};
+
 struct MigrationState
 {
     int64_t bandwidth_limit;
@@ -130,6 +142,12 @@ struct MigrationState
      * of the postcopy phase
      */
     unsigned long *sentmap;
+
+    /* Queue of outstanding page requests from the destination */
+    QemuMutex src_page_req_mutex;
+    QSIMPLEQ_HEAD(src_page_requests, MigrationSrcPageRequest) src_page_requests;
+    /* The RAMBlock used in the last src_page_request */
+    RAMBlock *last_req_rb;
 };
 
 void process_incoming_migration(QEMUFile *f);
@@ -259,6 +277,9 @@ size_t ram_control_save_page(QEMUFile *f, ram_addr_t block_offset,
                              ram_addr_t offset, size_t size,
                              uint64_t *bytes_sent);
 
+int ram_save_queue_pages(MigrationState *ms, const char *rbname,
+                         ram_addr_t start, ram_addr_t len);
+
 PostcopyState postcopy_state_get(MigrationIncomingState *mis);
 
 /* Set the state and return the old state */
diff --git a/include/qemu/typedefs.h b/include/qemu/typedefs.h
index 5f130fe..61b5b46 100644
--- a/include/qemu/typedefs.h
+++ b/include/qemu/typedefs.h
@@ -72,6 +72,7 @@ typedef struct QEMUSGList QEMUSGList;
 typedef struct QEMUSizedBuffer QEMUSizedBuffer;
 typedef struct QEMUTimerListGroup QEMUTimerListGroup;
 typedef struct QEMUTimer QEMUTimer;
+typedef struct RAMBlock RAMBlock;
 typedef struct Range Range;
 typedef struct SerialState SerialState;
 typedef struct SHPCDevice SHPCDevice;
diff --git a/migration/migration.c b/migration/migration.c
index 41f377c..2509798 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -26,6 +26,8 @@
 #include "qemu/thread.h"
 #include "qmp-commands.h"
 #include "trace.h"
+#include "exec/memory.h"
+#include "exec/address-spaces.h"
 
 #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */
 
@@ -496,6 +498,15 @@ static void migrate_fd_cleanup(void *opaque)
 
     migrate_fd_cleanup_src_rp(s);
 
+    /* This queue generally should be empty - but in the case of a failed
+     * migration might have some droppings in.
+     */
+    struct MigrationSrcPageRequest *mspr, *next_mspr;
+    QSIMPLEQ_FOREACH_SAFE(mspr, &s->src_page_requests, next_req, next_mspr) {
+        QSIMPLEQ_REMOVE_HEAD(&s->src_page_requests, next_req);
+        g_free(mspr);
+    }
+
     if (s->file) {
         trace_migrate_fd_cleanup();
         qemu_mutex_unlock_iothread();
@@ -614,6 +625,9 @@ MigrationState *migrate_init(const MigrationParams *params)
     s->state = MIGRATION_STATUS_SETUP;
     trace_migrate_set_state(MIGRATION_STATUS_SETUP);
 
+    qemu_mutex_init(&s->src_page_req_mutex);
+    QSIMPLEQ_INIT(&s->src_page_requests);
+
     s->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     return s;
 }
@@ -842,6 +856,23 @@ static void migrate_handle_rp_req_pages(MigrationState *ms, const char* rbname,
                                        ram_addr_t start, ram_addr_t len)
 {
     trace_migrate_handle_rp_req_pages(rbname, start, len);
+
+    /* Round everything up to our host page size */
+    long our_host_ps = getpagesize();
+    if (start & (our_host_ps-1)) {
+        long roundings = start & (our_host_ps-1);
+        start -= roundings;
+        len += roundings;
+    }
+    if (len & (our_host_ps-1)) {
+        long roundings = len & (our_host_ps-1);
+        len -= roundings;
+        len += our_host_ps;
+    }
+
+    if (ram_save_queue_pages(ms, rbname, start, len)) {
+        source_return_path_bad(ms);
+    }
 }
 
 /*
diff --git a/trace-events b/trace-events
index 8379c1f..3792d2e 100644
--- a/trace-events
+++ b/trace-events
@@ -1220,6 +1220,7 @@ migration_bitmap_sync_start(void) ""
 migration_bitmap_sync_end(uint64_t dirty_pages) "dirty_pages %" PRIu64""
 migration_throttle(void) ""
 ram_postcopy_send_discard_bitmap(void) ""
+ram_save_queue_pages(const char *rbname, size_t start, size_t len) "%s: start: %zx len: %zx"
 
 # hw/display/qxl.c
 disable qxl_interface_set_mm_time(int qid, uint32_t mm_time) "%d %d"
-- 
2.1.0