[vfio-users] How to split iommu group on [xeon e3-1220 v5 + supermicro x11ssh-ln4f]

Alex Williamson alex.l.williamson at gmail.com
Thu Apr 7 16:54:05 UTC 2016

On Thu, Apr 7, 2016 at 6:14 AM, Tran The Anh <anh.tranthe at thegioididong.com>

> Dear Mr. Williamson,
> Proxmox ve 4.1 has your ACS-override-patch included in the kernel.
> When "pcie_acs_override=downstream" added to kernel parameter, dmesg says
> "PCIe ACS overrides enabled; ..."
> However, iommu group 4 is still big.

The ACS override patch won't touch devices that report an ACS capability,
like the PCH root ports on 100-series chipsets, so that patch isn't
effective here.  The ACS override patch was only intended to assume
isolation when not provided by ACS, not to reject the isolation claims of
the hardware...  I guess I didn't foresee non-spec compliant ACS

> I have patched the pve-kernel with your Skylake-PCH-patch.
> It works now. IOMMU groups are separated. Each pcie device is in its own
> group.

Great.  Thanks,

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