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Re: [Xen-devel] [PATCH v3] passthrough/vtd: Don't DMA to the stack in queue_invalidate_wait()
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <JBeulich@xxxxxxxx>
- Date: Tue, 16 Jul 2019 16:33:59 +0000
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- Cc: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>
- Delivery-date: Tue, 16 Jul 2019 16:37:25 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHVO/L1K7bAkJ+VBki7BnAFJZRIEqbNcJ6A
- Thread-topic: [PATCH v3] passthrough/vtd: Don't DMA to the stack in queue_invalidate_wait()
On 16.07.2019 18:23, Andrew Cooper wrote:
> DMA-ing to the stack is 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.
>
> Fix the declaration of saddr in struct qinval_entry, to avoid a shift by
> two. The requirement here is that the DMA address is dword aligned,
> which is covered by poll_slot's type.
>
> This change does not address other issues. Correlating completions
> after a timeout with their request is a more complicated change.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <JBeulich@xxxxxxxx>
Must have been quite some time since v2 ...
Jan
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