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Re: [PATCH v2 2/2] VT-d: avoid infinite recursion on domain_context_mapping_one() error path
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Thu, 7 Apr 2022 09:51:30 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Paul Durrant <paul@xxxxxxx>
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On Thu, Apr 07, 2022 at 08:11:45AM +0200, Jan Beulich wrote:
> Despite the comment there infinite recursion was still possible, by
> flip-flopping between two domains. This is because prev_dom is derived
> from the DID found in the context entry, which was already updated by
> the time error recovery is invoked. Simply introduce yet another mode
> flag to prevent rolling back an in-progress roll-back of a prior
> mapping attempt.
>
> Also drop the existing recursion prevention for having been dead anyway:
> Earlier in the function we already bail when prev_dom == domain.
I wonder whether it would be cleaner to stash the previous context
entry if present and try to (re)set that one instead of recurring into
ourselves.
> Fixes: 8f41e481b485 ("VT-d: re-assign devices directly")
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Thanks, Roger.
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