From: Jan Beulich <jbeulich@suse.com>
To: Olaf Hering <olaf@aepfle.de>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <iwj@xenproject.org>, Wei Liu <wl@xen.org>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH] tools/libxenguest: Fix migration's debug option
Date: Mon, 5 Jul 2021 10:23:00 +0200 [thread overview]
Message-ID: <ed3ceecf-239f-9bd9-e040-5246c9b49f53@suse.com> (raw)
In-Reply-To: <20210705100228.4947ed4e.olaf@aepfle.de>
On 05.07.2021 10:02, Olaf Hering wrote:
> Am Mon, 5 Jul 2021 09:57:21 +0200
> schrieb Jan Beulich <jbeulich@suse.com>:
>
>> What is "the grant problem" referring to here? Neither anything above
>> nor the offending original commit has any reference to grants, or a
>> problem with them.
>
> When the guest is paused during final transit, the backends will
> continue to write into domU memory. As a result the final additional
> iteration to verify memory on both sides will always see errors.
I see. A similar problem then exists with at least the FIFO event
channel per-vCPU control blocks?
> The code has no way to know for which pfn such mismatches in page
> content can safely be ignored.
Well, in principle this can be known, but it's expensive: For a
paused domain the grant table can't change anymore. Any pages
referenced by a valid non-r/o grant table entry could in principle
change.
Jan
next prev parent reply other threads:[~2021-07-05 8:23 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 [this message]
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
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