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[Xen-devel] question about io path in the front/backend

To: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] question about io path in the front/backend
From: tgh <wwwwww4187@xxxxxxxxxxx>
Date: Thu, 15 Nov 2007 15:04:02 +0800
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hi
I have read some documents and wiki about split driver in xen,and I am confused about the I/O path ,in which a sys_read() pass through the domU and dom0,does sys_read() in the domU pass through vfs and ,say ,ext3fs in domU,and insert request into the requeest_queue of the frontend-driver,is it right? and then ,say domU sets up with a *.img file in the dom0, then what does frontend and backend driver do?
 does frontend transmit the request to the backend ,is it right?
and then what does backend driver do ? does backend transfer the request to the phyiscal driver in the dom0 ,is it right? or does backend transfer the request into some read()operation ,and submit it to the vfs and ,say,ext3fs in dom0, and do another relatively complete io path in the dom0,is it right? or if backend transfer the request to physical driver directly, how does the backend deal with the request's virtual address ,and how does backend manage bio buffer ,does physical driver and backend and frontend share the bio buffer in some way, or what does xen deal with it ?


I am confused about all that ,could someone help me
Thanks in advance

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