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Date: Fri, 2 Feb 2018 18:04:59 +0800
From: Peter Xu <peterx@redhat.com>
Message-ID: <20180202100459.GB4666@xz-mi>
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Subject: Re: [Qemu-devel] [PATCH] pcie-root-port: let it has higher migrate
 priority
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To: Marcel Apfelbaum <marcel@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, qemu-devel@nongnu.org, Alex Williamson <alex.williamson@redhat.com>, Juan Quintela <quintela@redhat.com>, Laurent Vivier <lvivier@redhat.com>

On Thu, Feb 01, 2018 at 10:01:31PM +0200, Marcel Apfelbaum wrote:

[...]

> Root ports can't be nested, anyway, I suppose the migration should
> follow the bus numbering order.

Could I ask whether this is a must?  And if yes, why?

> 
> The question now is what happens if the migration is happening before
> the guest firmware finishes assigning numbers to buses...

Do you mean that vIOMMU may fetch wrong context entries too?

Note that as long as vIOMMU DMAR is off globally, vIOMMU will not
fetch context entries at all.  So IMHO this problem should not happen
during the firmware execution time (assuming that the firmware should
not enable vIOMMU at all).

Thanks,

-- 
Peter Xu