Re: [Xen-devel] Pinning a DomU Guest data page from Hypervisor

To:	Tim Deegan <tim@xxxxxxx>
Subject:	Re: [Xen-devel] Pinning a DomU Guest data page from Hypervisor
From:	veerasena reddy <veeruyours@xxxxxxxxx>
Date:	Thu, 4 Aug 2011 11:43:22 +0530
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx
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Thanks a lot. I can make Guest not to reassign my data pages by doing dma_map_single() on all my data pages.

I will try that.
thanks again.

Regards,

VSR.

On Wed, Aug 3, 2011 at 11:43 PM, Tim Deegan <tim@xxxxxxx> wrote:

Hi,

At 23:20 +0530 on 03 Aug (1312413612), veerasena reddy wrote:
> By pinning, I mean to keep the data page always in main memory for the
> device to access. Once the device processes the page, i can unpin.
> Please correct me, if i understood page pinning concept wrongly.
> But, my goal is to keep the page in main memory until the device processes
> it.

If you want to stop _xen_ reassigning this frame (including any
hypervisor-level paging) you can just take a reference count (probably
you want a writeable-tyrp typecount using get_page_and_type()). But Xen
can't stop the guest OS from reusing the frame (including paging its
contents out), so you will need to address that inside the guest OS.

Tim.

--
Tim Deegan <tim@xxxxxxx>
Principal Software Engineer, Xen Platform Team
Citrix Systems UK Ltd. (Company #02937203, SL9 0BG)

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Re: [Xen-devel] Pinning a DomU Guest data page from Hypervisor