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Re: [Xen-devel] netfront.c: gnttab_query_foreign_access returns nonzero

To: "Kirk Allan" <kallan@xxxxxxxxxx>
Subject: Re: [Xen-devel] netfront.c: gnttab_query_foreign_access returns nonzero in network_tx_buf_gc
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Thu, 25 May 2006 21:05:05 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Steven Hand <steven.hand@xxxxxxxxxxxx>
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On 25 May 2006, at 20:58, Kirk Allan wrote:

Here's the serial output from a debug build of xen.  The domain_crash
does not happen on the non-debug xen.

So the problem is in netback driver, or in the map/unmap grant-table logic in Xen. The problem you saw in netfront is simply a knock-on symptom (given netfront's current inability to recover, the bail path there could more usefully be BUG() I suppose).

For some reason Xen has decided that the PTE that netback supplies when it tries to unmap a grant reference does not match up with the memory page that the grant reference grants access to.

 -- Keir

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