Re: [Xen-devel] Rebooting domu fails in nfs share exported from another domu on the same dom0

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

On 16/07/14 22:36, annie li wrote:
> Hi
> 
> I hit a problem in such scenario: vm1 is running and export nfs service,
> dom0 mount this nfs, and vm2 is booted in this nfs location. vm1 and vm2
> are running on the same dom0.
> 
> When this bug happens, the data flow is:  vm2 blkfront-> vm2 blkback->
> loop -> nfs file -> nfs client -> bridge priv1 -> vm1 vif -> vm1 netback
> -> vm1 netfront.
> 
> In above data flow, nfs implements direct io, blkfront and blkback uses
> grantmap. This makes page mapping works well through vm2 blkfront to vm1
> netback. However, when netback does grant copy, the error happens in
> this routine:

If it's the same error I was seeing (which I think it is), the problem
is due to trying to do a grant_copy with the PFN of a grant mapped page
in Dom0, which Xen refuses to perform.

I've never followed it up, but I think the problem should be fixed in
Linux, so that netback realises it is trying to perform a grant_copy to
a granted page, and use the grant ref instead of the PFN.

Roger.

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