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Date: Fri, 27 Jun 2014 18:54:09 -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

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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?


On Fri, Jun 27, 2014 at 5:49 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:

> Il 27/06/2014 21:41, Xiongzi Ge ha scritto:
>
>
>> When I studied the code, I found in migration.c,
>> bdrv_clear_incoming_migration_all();
>>
>> the cache of the bdrv devices will be deleted.
>>
>> Is this the one for the functions to be called after migration?
>>
>> Does the bdrv device need to be reopen or load state in block.c?
>>
>> I would like to find this function to add my new code.
>>
>
> This function is not going to do anything if your code is in "raw" format.
>  In particular, it 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.
>
> Paolo
>

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<div dir=3D"ltr">Hi Paolo,<div><br></div><div style>Thanks. I found a funct=
ion called bdrv_invalidate_cache() in qcow2.c. After migration, it will be =
called to invalidate the cache of the block device?=C2=A0</div></div><div c=
lass=3D"gmail_extra">
<br><br><div class=3D"gmail_quote">On Fri, Jun 27, 2014 at 5:49 PM, Paolo B=
onzini <span dir=3D"ltr">&lt;<a href=3D"mailto:pbonzini@redhat.com" target=
=3D"_blank">pbonzini@redhat.com</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex">
Il 27/06/2014 21:41, Xiongzi Ge ha scritto:<div><div class=3D"h5"><br>
<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">
<br>
When I studied the code, I found in migration.c,<br>
bdrv_clear_incoming_migration_<u></u>all();<br>
<br>
the cache of the bdrv devices will be deleted.<br>
<br>
Is this the one for the functions to be called after migration?<br>
<br>
Does the bdrv device need to be reopen or load state in block.c?<br>
<br>
I would like to find this function to add my new code.<br>
</blockquote>
<br></div></div>
This function is not going to do anything if your code is in &quot;raw&quot=
; format. =C2=A0In particular, it has *nothing* to do with the guest OS&#39=
;s cache. =C2=A0That cache is managed by the guest OS and, as I have alread=
y told you multiple times, there is *nothing* that QEMU can do about it.<br=
>

<br>
All you can do is use O_DIRECT in the guest.<span class=3D"HOEnZb"><font co=
lor=3D"#888888"><br>
<br>
Paolo<br>
</font></span></blockquote></div><br></div>

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