linux-kernel - Re: [PATCH] pci: quirk: Apply APM ACS quirk to XGene devices

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Date:   Thu, 20 Jul 2017 16:19:05 -0600
From:   Alex Williamson <alex.williamson@...hat.com>
To:     Feng Kan <fkan@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
        "Jonglih (Daniel) Yu" <jyu@....com>,
        "jcm@...hat.com" <jcm@...hat.com>
Subject: Re: [PATCH] pci: quirk: Apply APM ACS quirk to XGene devices

On Tue, 18 Jul 2017 22:37:00 -0700
Feng Kan <fkan@....com> wrote:

> >
> > I don't know what that means, does the hardware support an equivalent
> > to source validation or not?  
> 
> Yes, source validation is done through the smmu.

The SMMU does a context lookup based on the bdf, but if the root port
does not support SV, what is it that prevents the device from spoofing
a different bdf?  How does the smmu intercept this?  Thanks,

Alex
 
>   What's the response of the root port if
> > the downstream device issues a transaction spoofing devices not within
> > the bus number ranges of the bridge?  
> HW guys informs me there is way to disable transactions between root port.
> I will confirm later.
> 
> >  
> >> Alex, the goal here is to enable virtualization to work correctly.
> >> Please let me know if the
> >> above is sufficient. Much thanks.  
> >
> > Of course, but that means that the hardware vendor is vouching that
> > this device provides the equivalent isolation for each of the missing
> > components of ACS.  Claiming to have isolation capabilities that don't
> > exist would be irresponsible and put users of that hardware at risk.  
> Agreed, I believe we do have isolation in our case based on the conference
> we had today.
> 
> > Thanks,
> >
> > Alex