Re: [Xen-devel] [PATCH v6 4/5] xen: introduce XENMEM_exchange_and_pin and XENMEM_unpin

[David Vrabel <dvrabel@xxxxxxxxxx>]

On 30/09/13 13:30, Stefano Stabellini wrote:
> On Mon, 30 Sep 2013, Jan Beulich wrote:
>>>>> On 27.09.13 at 18:15, Stefano Stabellini 
>>>>> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
>>> Changes in v6:
>>> - do not change error paths;
>>> - crash the guest on pinning failure;
>>
>> Isn't that a little harsh?
> 
> I agree that this is harsh, but it's quite difficult to undo the
> page exchange that was previously done up to the point of failure. And a
> pinning error can only be caused by a misbehaviour of the guest.
> Overall this is a simple solution to a difficult problem.

Do you need to undo the exchange if the pinning failed?  Or could return
an error status of "exchanged but not pinned" and have the guest do the
right thing?

David

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