From: "Jan Beulich" <jbeulich@novell.com>
To: weidong.han@intel.com
Cc: xen-devel@lists.xensource.com, keir.fraser@eu.citrix.com
Subject: Re: [PATCH] Fixing ATS enabling for device assignment
Date: Wed, 19 May 2010 08:19:14 +0100 [thread overview]
Message-ID: <4BF39F03020000780005E03B@vpn.id2.novell.com> (raw)
>>> "Han, Weidong" 05/19/10 4:37 AM >>>
>Currently, Xen only enables ATS in Xen booting. When a ATS capable device is assigned to guest, ATS is actually not enabled because FLR before assignment causes it to be disabled. Thus ATS cannot be used in guest. This patch enables ATS in domain_context_mapping. This ensures ATS is enabled in assignment because FLR is earlier than domain_context_mapping call. Therefore ATS can be used in guest. This patch also implements disable_ats_device to disable ATS when the device is deassigned from a domain.
Hmm, this looks inconsistent to me: Iirc FLR is being done from the tools, so unless it is technically impossible to do FLR after domain_context_mapping(), the patch creates a hypervisor dependency on the tools (if nothing else, a latent bug - to be introduced the moment operation ordering changes in the tools).
Further, if ATS gets enabled at boot time, why would you want to disable it after de-assignment?
Finally (only partially related) - why are {en,dis}able_ats_device() architecture specific? PCI config space accesses really aren't I would think.
Jan
next reply other threads:[~2010-05-19 7:19 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-19 7:19 Jan Beulich [this message]
2010-05-19 9:12 ` [PATCH] Fixing ATS enabling for device assignment Weidong Han
-- strict thread matches above, loose matches on Subject: below --
2010-05-19 9:21 Jan Beulich
2010-05-19 9:52 ` Weidong Han
2010-05-19 2:33 Han, Weidong
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