From: Jan Beulich <jbeulich@suse.com>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
Xen-devel <xen-devel@lists.xenproject.org>,
Olaf Hering <olaf@aepfle.de>
Subject: Re: [PATCH] tools/libxenguest: Fix migration's debug option
Date: Mon, 5 Jul 2021 12:36:20 +0200 [thread overview]
Message-ID: <e4b6f75d-5aff-cc41-24f8-9aeb3caf09da@suse.com> (raw)
In-Reply-To: <f4301654-49c1-8b9a-a6c4-2b40d06641ae@citrix.com>
On 05.07.2021 12:06, Andrew Cooper wrote:
> On 05/07/2021 10:31, Jan Beulich wrote:
>> On 05.07.2021 11:25, Olaf Hering wrote:
>>> Am Mon, 5 Jul 2021 11:19:59 +0200
>>> schrieb Jan Beulich <jbeulich@suse.com>:
>>>
>>>> "The interface" being which one? The tool stack can map the guest's
>>>> grant table, so it is in the position to find out about all grants
>>>> without further hypervisor help.
>>> The interface means the code behind verify_frames.
>>>
>>> If there are indeed ways to query which pages belong to grants, how would the toolstack need to do that?
>> Map the grant table of the guest and walk it, recording any MFN for
>> which at least one valid r/w grant exists.
>
> That doesn't help - Its still racy with in-flight IO.
Well, I meant the recorded data to be used to simply not verify
those frames.
> Also with updates from Xen such as the wallclocks.
This doesn't occur for a paused domain, does it?
> The only way to fix the IO problem is to disconnect the blk/net rings
> before doing the final sweep for frames, but that clobbers any ability
> to restart the VM on the source side if things go wrong at the destination.
>
> I don't have an answer at all for the vcpu info frames.
Yeah, they fall in the same category as the FIFO control pages, as
they contain evtchn_{pending_sel,upcall_pending}.
Jan
prev parent reply other threads:[~2021-07-05 10:36 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-02 19:03 [PATCH] tools/libxenguest: Fix migration's debug option Andrew Cooper
2021-07-05 7:53 ` Olaf Hering
2021-07-05 7:57 ` Jan Beulich
2021-07-05 8:02 ` Olaf Hering
2021-07-05 8:23 ` Jan Beulich
2021-07-05 8:32 ` Olaf Hering
2021-07-05 9:19 ` Jan Beulich
2021-07-05 9:25 ` Olaf Hering
2021-07-05 9:31 ` Jan Beulich
2021-07-05 10:06 ` Andrew Cooper
2021-07-05 10:36 ` Jan Beulich [this message]
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