From: Alex Williamson <alex.williamson@redhat.com>
To: Ilya Lesokhin <ilyal@mellanox.com>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
Adi Menachem <adim@mellanox.com>
Subject: Re: Shouldn't VFIO virtualize the ATS capability?
Date: Wed, 9 Nov 2016 08:07:46 -0700 [thread overview]
Message-ID: <20161109080746.24dd79dd@t450s.home> (raw)
In-Reply-To: <VI1PR0502MB29579BD9AA9A2E85288798E4D4B90@VI1PR0502MB2957.eurprd05.prod.outlook.com>
On Wed, 9 Nov 2016 14:49:02 +0000
Ilya Lesokhin <ilyal@mellanox.com> wrote:
> I would virtualize the "ATS Control Register".
And do what?
> Regarding poor behavior, I couldn't really find what happens when ATS is misconfigured, but I would assume it can cause problems.
> The scenarios I'm concerned about are:
> 1. The guest enables translation caching, while the hypervisor thinks there are disabled -> Hypervisor won't issue invalidations.
Aren't invalidations issued by the iommu, why does the hypervisor need
to participate? How would a software entity induce an invalidation?
> 2. Smallest Translation Unit misconfiguration. Not sure if it will cause invalid access or only poor caching behavior.
>
> Thanks,
> Ilya
>
> > -----Original Message-----
> > From: Alex Williamson [mailto:alex.williamson@redhat.com]
> > Sent: Sunday, November 06, 2016 7:09 PM
> > To: Ilya Lesokhin <ilyal@mellanox.com>
> > Cc: linux-pci@vger.kernel.org; kvm@vger.kernel.org; bhelgaas@google.com
> > Subject: Re: Shouldn't VFIO virtualize the ATS capability?
> >
> > On Sun, 6 Nov 2016 11:13:09 +0000
> > Ilya Lesokhin <ilyal@mellanox.com> wrote:
> >
> > > Hi
> > > I've noticed that VFIO doesn't virtualize the ATS capability.
> > > It seems to me that translation caching and Smallest Translation Unit is
> > something you would want to control on the host. Am I wrong?
> >
> > What about those fields would we virtualize? Why does the host need to be
> > an intermediary? Can the user induce poor behavior with direct access to
> > them? Thanks,
> >
> > Alex
next prev parent reply other threads:[~2016-11-09 15:07 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-06 11:13 Shouldn't VFIO virtualize the ATS capability? Ilya Lesokhin
2016-11-06 17:08 ` Alex Williamson
2016-11-09 14:49 ` Ilya Lesokhin
2016-11-09 15:07 ` Alex Williamson [this message]
2016-11-09 15:25 ` Ilya Lesokhin
2016-11-09 15:53 ` Alex Williamson
2016-11-09 15:55 ` Ilya Lesokhin
2016-12-01 23:22 ` Alex Williamson
2016-12-02 7:45 ` Ilya Lesokhin
2016-12-02 15:58 ` Alex Williamson
2016-12-05 7:07 ` Ilya Lesokhin
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