Re: [Qemu-devel] [PATCH v2 for-qmp-1.6 3/4] dump: populate guest_phys_blocks

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/05/2013 10:19 AM, Laszlo Ersek wrote:
> While the machine is paused, in guest_phys_blocks_append() we register a
> one-shot MemoryListener, solely for the initial collection of the valid
> guest-physical memory ranges that happens at client registration time.
>
> For each range that is reported to guest_phys_blocks_set_memory(), we
> attempt to merge the range with adjacent (preceding, subsequent, or both)
> ranges. We use two hash tables for this purpose, both indexing the same
> ranges, just by different keys (guest-phys-start vs. guest-phys-end).
>
> Ranges can only be joined if they are contiguous in both guest-physical
> address space, and contiguous in host virtual address space.
>
> The "maximal" ranges that remain in the end constitute the guest-physical
> memory map that the dump will be based on.
>
> Related RHBZ: https://bugzilla.redhat.com/show_bug.cgi?id=981582

I would expect the ranges to be pretty large with MemoryListener, so 
there should be no need for merging (on IRC in fact you mentioned only 
10 calls to region_add).

So I would zap all the merging code.  Apart from this detail, this is 
great work!

Paolo

> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
> ---
>   include/sysemu/memory_mapping.h |    1 +
>   dump.c                          |    2 +-
>   memory_mapping.c                |  135 +++++++++++++++++++++++++++++++++++++++
>   3 files changed, 137 insertions(+), 1 deletions(-)
>
> diff --git a/include/sysemu/memory_mapping.h b/include/sysemu/memory_mapping.h
> index 53c2cd5..6723dc5 100644
> --- a/include/sysemu/memory_mapping.h
> +++ b/include/sysemu/memory_mapping.h
> @@ -66,6 +66,7 @@ void memory_mapping_list_init(MemoryMappingList *list);
>
>   void guest_phys_blocks_free(GuestPhysBlockList *list);
>   void guest_phys_blocks_init(GuestPhysBlockList *list);
> +void guest_phys_blocks_append(GuestPhysBlockList *list);
>
>   void qemu_get_guest_memory_mapping(MemoryMappingList *list, Error **errp);
>
> diff --git a/dump.c b/dump.c
> index 716fb1d..3fa33fc 100644
> --- a/dump.c
> +++ b/dump.c
> @@ -746,7 +746,7 @@ static int dump_init(DumpState *s, int fd, bool paging, bool has_filter,
>       s->length = length;
>
>       guest_phys_blocks_init(&s->guest_phys_blocks);
> -    /* FILL LIST */
> +    guest_phys_blocks_append(&s->guest_phys_blocks);
>
>       s->start = get_start_block(s);
>       if (s->start == -1) {
> diff --git a/memory_mapping.c b/memory_mapping.c
> index c70505b..efaabf8 100644
> --- a/memory_mapping.c
> +++ b/memory_mapping.c
> @@ -11,9 +11,13 @@
>    *
>    */
>
> +#include <glib.h>
> +
>   #include "cpu.h"
>   #include "exec/cpu-all.h"
>   #include "sysemu/memory_mapping.h"
> +#include "exec/memory.h"
> +#include "exec/address-spaces.h"
>
>   static void memory_mapping_list_add_mapping_sorted(MemoryMappingList *list,
>                                                      MemoryMapping *mapping)
> @@ -182,6 +186,137 @@ void guest_phys_blocks_init(GuestPhysBlockList *list)
>       QTAILQ_INIT(&list->head);
>   }
>
> +typedef struct GuestPhysListener {
> +    GHashTable *by_target_start;
> +    GHashTable *by_target_end;
> +    MemoryListener listener;
> +} GuestPhysListener;
> +
> +static void guest_phys_blocks_region_add(MemoryListener *listener,
> +                                         MemoryRegionSection *section)
> +{
> +    GuestPhysListener *g;
> +    uint64_t section_size;
> +    hwaddr target_start, target_end;
> +    uint8_t *host_addr;
> +    GuestPhysBlock *predecessor, *successor, *block;
> +    bool found;
> +
> +    /* we only care about RAM */
> +    if (!memory_region_is_ram(section->mr)) {
> +        return;
> +    }
> +
> +    g            = container_of(listener, GuestPhysListener, listener);
> +    section_size = int128_get64(section->size);
> +    target_start = section->offset_within_address_space;
> +    target_end   = target_start + section_size;
> +    host_addr    = memory_region_get_ram_ptr(section->mr) +
> +                   section->offset_within_region;
> +
> +    /* find continuity in guest physical address space */
> +    predecessor = g_hash_table_lookup(g->by_target_end,   &target_start);
> +    successor   = g_hash_table_lookup(g->by_target_start, &target_end);
> +
> +    /* we require continuity in host memory too */
> +    if (predecessor != NULL) {
> +        hwaddr predecessor_size = predecessor->target_end -
> +                                  predecessor->target_start;
> +        if (predecessor->host_addr + predecessor_size != host_addr) {
> +            predecessor = NULL;
> +        }
> +    }
> +    if (successor != NULL
> +        && host_addr + section_size != successor->host_addr) {
> +        successor = NULL;
> +    }
> +
> +    if (predecessor == NULL) {
> +        if (successor == NULL) {
> +            /* Isolated mapping, allocate it and add it to both tables. */
> +            block = g_malloc0(sizeof *block);
> +
> +            block->target_end = target_end;
> +            g_hash_table_insert(g->by_target_end, &block->target_end, block);
> +        } else {
> +            /* Mapping has successor only. Merge current into successor by
> +             * modifying successor's start. Successor's end doesn't change.
> +             */
> +            block = successor;
> +            found = g_hash_table_steal(g->by_target_start,
> +                                       &block->target_start);
> +            g_assert(found);
> +        }
> +        block->target_start = target_start;
> +        block->host_addr    = host_addr;
> +        g_hash_table_insert(g->by_target_start, &block->target_start, block);
> +        return;
> +    }
> +
> +    if (successor != NULL) {
> +        /* Mapping has both predecessor and successor. Delete the successor
> +         * and expand the predecessor to cover all three.
> +         */
> +        target_end = successor->target_end;
> +
> +        found = g_hash_table_steal(g->by_target_end, &successor->target_end);
> +        g_assert(found);
> +        found = g_hash_table_steal(g->by_target_start,
> +                                   &successor->target_start);
> +        g_assert(found);
> +
> +        g_free(successor);
> +    }
> +    /* otherwise, mapping has predecessor only */
> +
> +    /* Expand predecessor until @target_end. Predecessor's start doesn't
> +     * change.
> +     */
> +    block = predecessor;
> +    found = g_hash_table_steal(g->by_target_end, &block->target_end);
> +    g_assert(found);
> +
> +    block->target_end = target_end;
> +    g_hash_table_insert(g->by_target_end, &block->target_end, block);
> +}
> +
> +static void guest_phys_block_link(gpointer key, gpointer value,
> +                                  gpointer user_data)
> +{
> +    GuestPhysBlock *block = value;
> +    GuestPhysBlockList *list = user_data;
> +
> +    QTAILQ_INSERT_TAIL(&list->head, block, next);
> +    ++list->num;
> +}
> +
> +void guest_phys_blocks_append(GuestPhysBlockList *list)
> +{
> +    GHashFunc hash_func;
> +    GEqualFunc equal_func;
> +    GuestPhysListener g = { 0 };
> +
> +    if (sizeof(hwaddr) == sizeof(uint64_t)) {
> +        hash_func  = &g_int64_hash;
> +        equal_func = &g_int64_equal;
> +    } else {
> +        hash_func  = &g_int_hash;
> +        equal_func = &g_int_equal;
> +    }
> +
> +    g.by_target_start = g_hash_table_new(hash_func, equal_func);
> +    g.by_target_end   = g_hash_table_new(hash_func, equal_func);
> +
> +    g.listener.region_add = &guest_phys_blocks_region_add;
> +    memory_listener_register(&g.listener, &address_space_memory);
> +    memory_listener_unregister(&g.listener);
> +
> +    g_hash_table_foreach(g.by_target_start, &guest_phys_block_link, list);
> +
> +    g_hash_table_destroy(g.by_target_end);
> +    g_hash_table_destroy(g.by_target_start);
> +}
> +
>   static CPUState *find_paging_enabled_cpu(CPUState *start_cpu)
>   {
>       CPUState *cpu;
>