From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>
Subject: Re: [PATCH v3 15/16] iommu: introduce page response function
Date: Fri, 8 Dec 2017 13:51:48 +0000
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To: Alex Williamson <alex.williamson-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Lan Tianyu <tianyu.lan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Greg Kroah-Hartman <gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>, Rafael Wysocki <rafael.j.wysocki-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Will Deacon <Will.Deacon-5wv7dgnIgG8@public.gmane.org>, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Jean Delvare <khali-PUYAD+kWke1g9hUCZPvPmw@public.gmane.org>, "Kumar,
	Sanjay K" <sanjay.k.kumar-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, David Woodhouse <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
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On 07/12/17 21:56, Alex Williamson wrote:
[...]
>> Seems like VFIO should enforce this quota, since the IOMMU layer doesn't
>> know which device is assigned to which VM. If it's the IOMMU that enforces
>> quotas per device and a VM has 15 devices assigned, then the guest can
>> still DoS the IOMMU.
> 
> VFIO also doesn't know about VMs.  We know that devices attached to the
> same container are probably used by the same user, but once we add
> viommu, each device(group) uses its own container and we have no idea
> they're associated.  So, no to VM based accounting, and it seems like
> an IOMMU problem, X number of outstanding requests per device.  Thanks,

Ok. It's not clear anyway how the architecture and implementations expect
us to virtualize stall, I'll try to clarify it.

Thanks,
Jean