Re: [Xen-devel] [PATCH for-4.10 v2] passthrough/vtd: Don't DMA to the stack in queue_invalidate_wait()

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Saturday, October 21, 2017 1:55 AM
> 
> On 20/10/17 08:12, Jan Beulich wrote:
> >>>> On 19.10.17 at 18:22, <andrew.cooper3@xxxxxxxxxx> wrote:
> >> DMA-ing to the stack is generally considered bad practice.  In this case, 
> >> if
> a
> >> timeout occurs because of a sluggish device which is processing the
> request,
> >> the completion notification will corrupt the stack of a subsequent
> deeper call
> >> tree.
> >>
> >> Place the poll_slot in a percpu area and DMA to that instead.
> >>
> >> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Please could you extend the commit message to state the issue
> > remaining with using a single per-CPU slot? With that
> > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> How about this?
> 
> Note: This change does not address other issues with the current
> implementation, such as once a timeout has been suffered, subsequent
> completions can't be correlated with their requests.
> 

Can you increase the poll data +1 every time when a new wait
comes?

Thanks
Kevin
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