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Re: [vfio-users] Supermicro C7Z170-OCE, a rather interesing Skylake Motherboard for VFIO if PEX8747 downstream ACS works



On Fri, Dec 25, 2015 at 9:43 PM, Zir Blazer <zir_blazer hotmail com> wrote:
In a hypothetical case that I drop such Dual GPU card in a slot attached to the Chipset, it means that I would get isolation there, but not if connected to the Processor. Is that correct, too?

I'm not sure how to phrase it differently that I have in my blog post, each interconnect component, whether a root port, switch port, or multifunction device, needs to support ACS or ACS-equivalent isolation to have separate IOMMU groups.  Isolation is lost at the furthest upstream device lacking ACS.  In your scenario, yes, if the chipset root ports support ACS-equivalent isolation and the switch supports native ACS, then isolation is present through the downstream switch ports.  Nvidia GRID cards make use of such switches and when installed into a downstream port supporting isolation, each GPU is exposed within its own IOMMU group.  Thanks,

Alex

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