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Re: [Xen-devel] Re: how to handle paged hypercall args?


  • To: Olaf Hering <olaf@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • From: Keir Fraser <keir@xxxxxxx>
  • Date: Thu, 11 Nov 2010 20:08:59 +0000
  • Cc:
  • Delivery-date: Thu, 11 Nov 2010 12:09:54 -0800
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  • Thread-topic: [Xen-devel] Re: how to handle paged hypercall args?

On 11/11/2010 14:33, "Olaf Hering" <olaf@xxxxxxxxx> wrote:

> So is that an acceptable way to deal with the HVMCOPY_gfn_paged_out
> return codes from __hvm_copy?
> Or should I explore some different way, like spinning there and possible
> let other threads-of-execution make progress while waiting for the gfns
> to come back?

You can't just spin because Xen is not preemptible. If it were a single CPU
system for example, no other thread would ever run again. You have to 'spin'
via a preemptible loop that returns to guest context and then back into the
hypercall. Which appears to be what you're doing.

 -- Keir



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