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    SubjectRe: [PATCH v4 06/17] PCI: add SIOV and IMS capability detection
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    > On Fri, Nov 06 2020 at 09:14, Jason Gunthorpe wrote:
    >> On Fri, Nov 06, 2020 at 09:48:34AM +0000, Tian, Kevin wrote:
    >> For instance you could put a "disable IMS" flag in the ACPI tables, in
    >> the config space of the emuulated root port, or any other areas that
    >> clearly belong to the platform.
    >>
    >> The OS logic would be
    >> - If no IMS information found then use IMS (Bare metal)
    >> - If the IMS disable flag is found then
    >> - If (future) hypercall available and the OS knows how to use it
    >> then use IMS
    >> - If no hypercall found, or no OS knowledge, fail IMS
    >
    > That does not work because an older hypervisor would not have that
    > disable flag and the guest kernel would assume to be on bare metal (if
    > no other indicators are there).

    In the absence of a forward-thinking design from Intel perhaps we could
    use the existence of an IOMMU with interrupt remapping and not caching
    mode as the indication that it's bare metal?

    --
    dwmw2

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