From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: [PATCH v9] new config option vtsc_tolerance_khz to
 avoid TSC emulation
Date: Thu, 7 Jun 2018 15:47:43 +0200
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To: Jan Beulich <JBeulich@suse.com>
Cc: Tim Deegan <tim@xen.org>, Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wei.liu2@citrix.com>, George Dunlap <George.Dunlap@eu.citrix.com>, Andrew Cooper <andrew.cooper3@citrix.com>, Ian Jackson <Ian.Jackson@eu.citrix.com>, Marek Marczykowski <marmarek@invisiblethingslab.com>, xen-devel@lists.xen.org, Julien Grall <julien.grall@arm.com>
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Am Thu, 07 Jun 2018 07:31:26 -0600
schrieb "Jan Beulich" <JBeulich@suse.com>:

> Hmm, I find this description concerning. Is the field reliably zero when
> coming from older Xen, or is it not?

It depends on how old.
If the other sending side has write_tsc_info from 4.6+, then _res1 is zero.
If it is older, the XC_SAVE_ID_TSC_INFO is eventually not handled anymore.
At least I could not find the relevant code, even in staging-4.6.
But then, it is unlikely that migration from 4.5 to 4.6 did not work.

Also, in general the input comes from "remote". So it is untrusted.

Olaf

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