Re: [Qemu-devel] [PATCH 3/8] migration: support to detect compressionand decompression errors

[Xiao Guangrong]

On 03/19/2018 03:56 PM, address@hidden wrote:
> Hi, guangrong
> > @@ -1051,11 +1052,13 @@ static int do_compress_ram_page(QEMUFile *f, z_stream 
> > *stream, RAMBlock *block,
> > {
> > RAMState *rs = ram_state;
> > int bytes_sent, blen;
> > -    uint8_t *p = block->host + (offset & TARGET_PAGE_MASK);
> > +    uint8_t buf[TARGET_PAGE_SIZE], *p;
>
> > +    p = block->host + (offset & TARGET_PAGE_MASK);
> > bytes_sent = save_page_header(rs, f, block, offset |
> > RAM_SAVE_FLAG_COMPRESS_PAGE);
> > -    blen = qemu_put_compression_data(f, stream, p, TARGET_PAGE_SIZE);
> > +    memcpy(buf, p, TARGET_PAGE_SIZE);
> > +    blen = qemu_put_compression_data(f, stream, buf, TARGET_PAGE_SIZE);
> Memory copy operation for every page to be compressed is not cheap, especially
> when the page number is huge, and it may be not necessary for pages never
> updated during migration.

This is only for 4k page.

> Is there any possibility that we can distinguish the real compress/decompress
> errors from those being caused by source VM updating? Such as the return
> value of qemu_uncompress(distinguish Z_DATA_ERROR and other error codes
> returned by inflate())?

Unfortunately, no. :(