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From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v5 7/9] block: don't make snapshots for
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To: Pavel Dovgalyuk <dovgaluk@ispras.ru>
Cc: Kevin Wolf <kwolf@redhat.com>, Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>, qemu-devel@nongnu.org, peter maydell <peter.maydell@linaro.org>, quintela@redhat.com, jasowang@redhat.com, mst@redhat.com, mreitz@redhat.com, qemu-block@nongnu.org



> I've investigated this issue.
> This command line works ok:
>  -drive
>  driver=blkreplay,if=none,image.driver=file,image.filename=testdisk.qcow,id=img-blkreplay
>  -device ide-hd,drive=img-blkreplay
> 
> And this does not:
>  -drive
> driver=blkreplay,if=none,image.driver=qcow2,image.file.driver=file,image.file.filename=testdisk.qcow
> ,id=img-blkreplay
>  -device ide-hd,drive=img-blkreplay
> 
> QEMU hangs at some moment of replay.
> 
> I found that some dma requests do not pass through the blkreplay driver
> due to the following line in block-backend.c:
>     return bdrv_co_preadv(blk->root, offset, bytes, qiov, flags);
> 
> This line passes read request directly to qcow driver and blkreplay cannot
> process it to make deterministic.

I don't understand, blk->root should be the blkreplay here.

Paolo