Re: [Qemu-devel] [PATCH 11/29] memory: include DIRTY_MEMORY_MIGRATION in the dirty log mask

[Fam Zheng <famz@redhat.com>]

On Mon, 04/27 18:28, Paolo Bonzini wrote:
> The separate handling of DIRTY_MEMORY_MIGRATION, which does not
> call log_start/log_stop callbacks when it changes in a region's
> dirty logging mask, has caused several bugs.
> 
> One recent example is commit 4cc856f (kvm-all: Sync dirty-bitmap from
> kvm before kvm destroy the corresponding dirty_bitmap, 2015-04-02).
> Another performance problem is that KVM keeps tracking dirty pages
> after a failed live migration, which causes bad performance due to
> disallowing huge page mapping.
> 
> This patch removes the root cause of the problem by reporting
> DIRTY_MEMORY_MIGRATION changes via log_start and log_stop.
> Note that we now have to rebuild the FlatView when global dirty
> logging is enabled or disabled; this ensures that log_start and
> log_stop callbacks are invoked.
> 
> This will also be used to make the setting of bitmaps conditional.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  memory.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/memory.c b/memory.c
> index 1966347..174cd15 100644
> --- a/memory.c
> +++ b/memory.c
> @@ -537,7 +537,7 @@ static void render_memory_region(FlatView *view,
>      remain = clip.size;
>  
>      fr.mr = mr;
> -    fr.dirty_log_mask = mr->dirty_log_mask;
> +    fr.dirty_log_mask = memory_region_get_dirty_log_mask(mr);
>      fr.romd_mode = mr->romd_mode;
>      fr.readonly = readonly;
>  
> @@ -1329,7 +1329,11 @@ bool memory_region_is_skip_dump(MemoryRegion *mr)
>  
>  uint8_t memory_region_get_dirty_log_mask(MemoryRegion *mr)
>  {
> -    return mr->dirty_log_mask;
> +    uint8_t mask = mr->dirty_log_mask;
> +    if (global_dirty_log) {
> +        mask |= (1 << DIRTY_MEMORY_MIGRATION);

This is ugly, but I don't know how to do differently. :(

> +    }
> +    return mask;
>  }
>  
>  bool memory_region_is_logging(MemoryRegion *mr, uint8_t client)
> @@ -1892,10 +1896,20 @@ void memory_global_dirty_log_start(void)
>  {
>      global_dirty_log = true;
>      MEMORY_LISTENER_CALL_GLOBAL(log_global_start, Forward);
> +
> +    /* Refresh DIRTY_LOG_MIGRATION bit.  */
> +    memory_region_transaction_begin();
> +    memory_region_update_pending = true;
> +    memory_region_transaction_commit();
>  }
>  
>  void memory_global_dirty_log_stop(void)
>  {
> +    /* Refresh DIRTY_LOG_MIGRATION bit.  */
> +    memory_region_transaction_begin();
> +    memory_region_update_pending = true;
> +    memory_region_transaction_commit();
> +
>      global_dirty_log = false;

Shouldn't this go before memory_region_transaction_begin?

Fam