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Re: [Qemu-devel] [PATCH for-3.0 3/9] migration: fix incorrect bitmap siz
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [PATCH for-3.0 3/9] migration: fix incorrect bitmap size calculation |
Date: |
Thu, 5 Jul 2018 10:38:01 +0100 |
User-agent: |
Mutt/1.10.0 (2018-05-17) |
* Peter Xu (address@hidden) wrote:
> The calculation on size of received bitmap is incorrect for postcopy
> recovery. Here we wanted to let the size to cover all the valid bits in
> the bitmap, we should use DIV_ROUND_UP() instead of a division.
>
> For example, a RAMBlock with size=4K (which contains only one single 4K
> page) will have nbits=1, then nbits/8=0, then the real bitmap won't be
> sent to source at all.
>
> Signed-off-by: Peter Xu <address@hidden>
Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> ---
> migration/ram.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/migration/ram.c b/migration/ram.c
> index fbeb23f750..203c691ded 100644
> --- a/migration/ram.c
> +++ b/migration/ram.c
> @@ -235,7 +235,7 @@ int64_t ramblock_recv_bitmap_send(QEMUFile *file,
> bitmap_to_le(le_bitmap, block->receivedmap, nbits);
>
> /* Size of the bitmap, in bytes */
> - size = nbits / 8;
> + size = DIV_ROUND_UP(nbits, 8);
>
> /*
> * size is always aligned to 8 bytes for 64bit machines, but it
> @@ -3944,7 +3944,7 @@ int ram_dirty_bitmap_reload(MigrationState *s, RAMBlock
> *block)
> int ret = -EINVAL;
> QEMUFile *file = s->rp_state.from_dst_file;
> unsigned long *le_bitmap, nbits = block->used_length >> TARGET_PAGE_BITS;
> - uint64_t local_size = nbits / 8;
> + uint64_t local_size = DIV_ROUND_UP(nbits, 8);
> uint64_t size, end_mark;
>
> trace_ram_dirty_bitmap_reload_begin(block->idstr);
> --
> 2.17.1
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
- [Qemu-devel] [PATCH for-3.0 0/9] migration: postcopy recovery unit test, bug fixes, Peter Xu, 2018/07/04
- [Qemu-devel] [PATCH for-3.0 1/9] migration: simplify check to use qemu file buffer, Peter Xu, 2018/07/04
- [Qemu-devel] [PATCH for-3.0 2/9] migration: loosen recovery check when load vm, Peter Xu, 2018/07/04
- [Qemu-devel] [PATCH for-3.0 3/9] migration: fix incorrect bitmap size calculation, Peter Xu, 2018/07/04
- [Qemu-devel] [PATCH for-3.0 4/9] tests: introduce migrate_postcopy_* helpers, Peter Xu, 2018/07/04
- Re: [Qemu-devel] [PATCH for-3.0 4/9] tests: introduce migrate_postcopy_* helpers, Dr. David Alan Gilbert, 2018/07/05
- Re: [Qemu-devel] [PATCH for-3.0 4/9] tests: introduce migrate_postcopy_* helpers, Juan Quintela, 2018/07/05
- [Qemu-devel] [PATCH for-3.0 5/9] tests: allow migrate() to take extra flags, Peter Xu, 2018/07/04