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    SubjectRe: [PATCH 1/1] iommu/vt-d: Add opt-in for ATS support on discrete devices
    On Fri, Mar 03, 2023 at 08:19:29AM +0000, Tian, Kevin wrote:
    > > From: Jason Gunthorpe <jgg@nvidia.com>
    > > Sent: Thursday, March 2, 2023 1:43 AM
    > >
    > > If Intel BIOS's have populated the "satcu" to say that ATS is not
    > > supported by the HW when the HW supports ATS perfectly fine, then get
    > > the BIOS fixed or patch the ACPI until it is fixed. The BIOS should
    > > not be saying that the HW does not support ATS when it does, it is a
    > > simple BIOS bug.
    > >
    >
    > That is not the purpose of SATC.
    >
    > The ATS support in VT-d side is reported in two interfaces:
    >
    > 1) "Device-TLB support" in Extended Capability Register;
    > 2) Root port ATS capability in ACPI ATSR structure;
    >
    > A device gets ATS enabled if 1/2 are true and !pdev->untrusted. Same
    > as SMMU does.
    >
    > The main purpose of SATC is to describe which ATS-capable integrated
    > device meets the requirements of securely using ATS as stated in VT-d
    > spec 4.4.

    Then it should be mapped to pdev->untrusted and possibly
    pdev->untrusted to be enhanced to be more descriptive.

    iommu driver and BIOS should have no role in security policy beyond
    feeding in data to a common policy engine.

    Jason

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