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    Subject[PATCH 4.0 039/105] iommu/vt-d: Fix passthrough mode with translation-disabled devices
    Date
    4.0-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: David Woodhouse <David.Woodhouse@intel.com>

    commit 4ed6a540fab8ea4388c1703b73ecfed68a2009d1 upstream.

    When we use 'intel_iommu=igfx_off' to disable translation for the
    graphics, and when we discover that the BIOS has misconfigured the DMAR
    setup for I/OAT, we use a special DUMMY_DEVICE_DOMAIN_INFO value in
    dev->archdata.iommu to indicate that translation is disabled.

    With passthrough mode, we were attempting to dereference that as a
    normal pointer to a struct device_domain_info when setting up an
    identity mapping for the affected device.

    This fixes the problem by making device_to_iommu() explicitly check for
    the special value and indicate that no IOMMU was found to handle the
    devices in question.

    Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/iommu/intel-iommu.c | 13 ++++++++-----
    1 file changed, 8 insertions(+), 5 deletions(-)

    --- a/drivers/iommu/intel-iommu.c
    +++ b/drivers/iommu/intel-iommu.c
    @@ -673,6 +673,11 @@ static void domain_update_iommu_cap(stru
    domain->iommu_superpage = domain_update_iommu_superpage(NULL);
    }

    +static int iommu_dummy(struct device *dev)
    +{
    + return dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO;
    +}
    +
    static struct intel_iommu *device_to_iommu(struct device *dev, u8 *bus, u8 *devfn)
    {
    struct dmar_drhd_unit *drhd = NULL;
    @@ -682,6 +687,9 @@ static struct intel_iommu *device_to_iom
    u16 segment = 0;
    int i;

    + if (iommu_dummy(dev))
    + return NULL;
    +
    if (dev_is_pci(dev)) {
    pdev = to_pci_dev(dev);
    segment = pci_domain_nr(pdev->bus);
    @@ -2974,11 +2982,6 @@ static inline struct dmar_domain *get_va
    return __get_valid_domain_for_dev(dev);
    }

    -static int iommu_dummy(struct device *dev)
    -{
    - return dev->archdata.iommu == DUMMY_DEVICE_DOMAIN_INFO;
    -}
    -
    /* Check if the dev needs to go through non-identity map and unmap process.*/
    static int iommu_no_mapping(struct device *dev)
    {

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