[Qemu-devel] [PATCH v1 2/2] migration: add bitmap for copied page

[Alexey Perevalov]

This patch adds ability to track down already copied
pages, it's necessary for calculation vCPU block time in
postcopy migration feature, maybe for restore after
postcopy migration failure.
Also it's necessary to solve shared memory issue in
postcopy livemigration. Information about copied pages
will be transferred to the software virtual bridge
(e.g. OVS-VSWITCHD), to avoid fallocate (unmap) for
already copied pages. fallocate syscall is required for
remmaped shared memory, due to remmaping itself blocks
ioctl(UFFDIO_COPY, ioctl in this case will end with EEXIT
error (struct page is exists after remmap).

Bitmap is placed into RAMBlock as another postcopy/precopy
related bitmaps.

copied bitmap is not releasing due to ramblocks is not releasing
too.

Signed-off-by: Alexey Perevalov <address@hidden>
---
 include/exec/ram_addr.h       |  3 +++
 include/migration/migration.h |  3 +++
 migration/postcopy-ram.c      |  7 ++++++
 migration/ram.c               | 54 ++++++++++++++++++++++++++++++++++++++++++-
 migration/ram.h               |  5 ++++
 migration/savevm.c            |  1 +
 6 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/include/exec/ram_addr.h b/include/exec/ram_addr.h
index 140efa8..56cdf16 100644
--- a/include/exec/ram_addr.h
+++ b/include/exec/ram_addr.h
@@ -47,6 +47,9 @@ struct RAMBlock {
      * of the postcopy phase
      */
     unsigned long *unsentmap;
+    /* bitmap of already copied pages in postcopy */
+    unsigned long *copiedmap;
+    size_t nr_copiedmap;
 };
 
 static inline bool offset_in_ramblock(RAMBlock *b, ram_addr_t offset)
diff --git a/include/migration/migration.h b/include/migration/migration.h
index 79b5484..8005c11 100644
--- a/include/migration/migration.h
+++ b/include/migration/migration.h
@@ -226,4 +226,7 @@ void savevm_skip_configuration(void);
 int global_state_store(void);
 void global_state_store_running(void);
 
+size_t get_copiedmap_size(RAMBlock *rb);
+void movecopiedmap(void *dst, RAMBlock *rb, size_t len);
+
 #endif
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
index f6244ee..e13b22e 100644
--- a/migration/postcopy-ram.c
+++ b/migration/postcopy-ram.c
@@ -576,6 +576,13 @@ int postcopy_place_page(MigrationIncomingState *mis, void 
*host, void *from,
     copy_struct.len = pagesize;
     copy_struct.mode = 0;
 
+
+    /* copied page isn't feature of blocktime calculation,
+     * it's more general entity, so keep it here,
+     * but gup betwean two following operation could be high,
+     * and in this case blocktime for such small interval will be lost */
+    set_copiedmap_by_addr(host, rb);
+
     /* copy also acks to the kernel waking the stalled thread up
      * TODO: We can inhibit that ack and only do it if it was requested
      * which would be slightly cheaper, but we'd have to be careful
diff --git a/migration/ram.c b/migration/ram.c
index 4ed7c2c..8466e59 100644
--- a/migration/ram.c
+++ b/migration/ram.c
@@ -149,6 +149,58 @@ out:
     return ret;
 }
 
+void init_copiedmap(void)
+{
+    RAMBlock *rb;
+    RAMBLOCK_FOREACH(rb) {
+        unsigned long pages;
+        pages = rb->max_length >> find_first_bit(&rb->page_size,
+                8 * sizeof(rb->page_size));
+        /* need for destination, bitmap_new calls
+         * g_try_malloc0 and this function
+         * Attempts to allocate @n_bytes, initialized to 0'sh */
+        rb->copiedmap = bitmap_new(pages);
+        rb->nr_copiedmap = pages;
+    }
+}
+
+static unsigned long int get_copied_bit_offset(void *host_addr, RAMBlock *rb)
+{
+    uint64_t host_addr_offset = (uint64_t)(uintptr_t)(host_addr
+                                                      - (void *)rb->host);
+    int page_shift = find_first_bit(&rb->page_size, 8 * sizeof(rb->page_size));
+
+    return host_addr_offset >> page_shift;
+}
+
+int test_copiedmap_by_addr(void *host_addr, RAMBlock *rb)
+{
+    return test_bit(get_copied_bit_offset(host_addr, rb), rb->copiedmap);
+}
+
+void set_copiedmap_by_addr(void *host_addr, RAMBlock *rb)
+{
+    set_bit_atomic(get_copied_bit_offset(host_addr, rb), rb->copiedmap);
+}
+
+size_t get_copiedmap_size(RAMBlock *rb)
+{
+    return rb->nr_copiedmap;
+}
+
+/*
+ * This function copies copiedmap from RAMBlock into
+ * dst memory region
+ *
+ * @dst destination address
+ * @rb RAMBlock source
+ * @len length in bytes
+ */
+void movecopiedmap(void *dst, RAMBlock *rb, size_t len)
+{
+    memcpy(dst, rb->copiedmap, len);
+}
+
 /*
  * An outstanding page request, on the source, having been received
  * and queued
@@ -1852,11 +1904,11 @@ int ram_discard_range(const char *rbname, uint64_t 
start, size_t length)
 {
     int ret = -1;
 
-    trace_ram_discard_range(rbname, start, length);
 
     rcu_read_lock();
     RAMBlock *rb = qemu_ram_block_by_name(rbname);
 
+    trace_ram_discard_range(rbname, start, length);
     if (!rb) {
         error_report("ram_discard_range: Failed to find block '%s'", rbname);
         goto err;
diff --git a/migration/ram.h b/migration/ram.h
index c9563d1..dc781c1 100644
--- a/migration/ram.h
+++ b/migration/ram.h
@@ -67,4 +67,9 @@ int ram_discard_range(const char *block_name, uint64_t start, 
size_t length);
 int ram_postcopy_incoming_init(MigrationIncomingState *mis);
 
 void ram_handle_compressed(void *host, uint8_t ch, uint64_t size);
+
+void init_copiedmap(void);
+int test_copiedmap_by_addr(void *host_addr, RAMBlock *rb);
+void set_copiedmap_by_addr(void *host_addr, RAMBlock *rb);
+
 #endif
diff --git a/migration/savevm.c b/migration/savevm.c
index 9c320f5..7b3726a 100644
--- a/migration/savevm.c
+++ b/migration/savevm.c
@@ -1385,6 +1385,7 @@ static int 
loadvm_postcopy_handle_advise(MigrationIncomingState *mis)
         return -1;
     }
 
+    init_copiedmap();
     remote_pagesize_summary = qemu_get_be64(mis->from_src_file);
     local_pagesize_summary = ram_pagesize_summary();
 
-- 
1.9.1