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Date: Mon, 30 Jun 2014 10:03:28 -0400
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From: Xiongzi Ge <gexxx132@umn.edu>
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Subject: Re: [Qemu-devel] The first function called after migration for a
	block device
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: qemu-devel@nongnu.org

--047d7b3a88fc98912d04fd0e1f9d
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I tried. It invalidated the cache of the block device after migration. So,
here, we can use a new cache for the block device after migration. Is it
right?  I can implement a simple block driver in block/ directory.


On Mon, Jun 30, 2014 at 6:48 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:

> Il 28/06/2014 00:54, Xiongzi Ge ha scritto:
>
>  Hi Paolo,
>>
>> Thanks. I found a function called bdrv_invalidate_cache() in qcow2.c.
>> After migration, it will be called to invalidate the cache of the block
>> device?
>>
>
> Let me quote again:
>
>      This function has *nothing* to do with the guest OS's
>>>
>>>     cache.  That cache is managed by the guest OS and, as I have already
>>>     told you multiple times, there is *nothing* that QEMU can do about
>>> it.
>>>
>>>     All you can do is use O_DIRECT in the guest.
>>>
>>
> Did you even *try* to understand this?!?
>
> Paolo
>
>

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<div dir=3D"ltr">I tried. It invalidated the cache of the block device afte=
r migration. So, here, we can use a new cache for the block device after mi=
gration. Is it right?=C2=A0 I can implement a simple block driver in block/=
 directory. <br>
</div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">On Mon,=
 Jun 30, 2014 at 6:48 AM, Paolo Bonzini <span dir=3D"ltr">&lt;<a href=3D"ma=
ilto:pbonzini@redhat.com" target=3D"_blank">pbonzini@redhat.com</a>&gt;</sp=
an> wrote:<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">Il 28/06/2014 00:54, Xiongzi Ge ha scritto:<=
div class=3D""><br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
Hi Paolo,<br>
<br>
Thanks. I found a function called bdrv_invalidate_cache() in qcow2.c.<br>
After migration, it will be called to invalidate the cache of the block<br>
device?<br>
</blockquote>
<br></div>
Let me quote again:<br>
<br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex"><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
=C2=A0 =C2=A0 This function has *nothing* to do with the guest OS&#39;s<div=
 class=3D""><br>
=C2=A0 =C2=A0 cache. =C2=A0That cache is managed by the guest OS and, as I =
have already<br>
=C2=A0 =C2=A0 told you multiple times, there is *nothing* that QEMU can do =
about it.<br>
<br>
=C2=A0 =C2=A0 All you can do is use O_DIRECT in the guest.<br>
</div></blockquote></blockquote>
<br>
Did you even *try* to understand this?!?<span class=3D"HOEnZb"><font color=
=3D"#888888"><br>
<br>
Paolo<br>
<br>
</font></span></blockquote></div><br></div>

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