Re: [Xen-devel] [PATCH RFC 01/44] 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: Friday, January 5, 2018 4:21 AM
> 
> 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.
> 
> 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.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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