On Mon, Nov 12, 2018 at 07:06:27PM +0300, Mika Westerberg wrote: > Currently Linux automatically enables ATS (Address Translation Service) > for any device that supports it (and IOMMU is turned on). ATS is used to > accelerate DMA access as the device can cache translations locally so > there is no need to do full translation on IOMMU side. However, as > pointed out in [1] ATS can be used to bypass IOMMU based security > completely by simply sending PCIe read/write transaction with AT > (Address Translation) field set to "translated". > > To mitigate this modify the Intel IOMMU code so that it does not enable > ATS for any device that is marked as being external. In case this turns > out to cause performance issues we may selectively allow ATS based on > user decision but currently use big hammer and disable it completely to > be on the safe side. > > [1] https://www.repository.cam.ac.uk/handle/1810/274352 > > Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> Reviewed-by: Ashok Raj <ashok.raj@xxxxxxxxx> > --- > drivers/iommu/intel-iommu.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index ada786b05a59..b79788da6971 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -1473,7 +1473,8 @@ static void iommu_enable_dev_iotlb(struct device_domain_info *info) > if (info->pri_supported && !pci_reset_pri(pdev) && !pci_enable_pri(pdev, 32)) > info->pri_enabled = 1; > #endif > - if (info->ats_supported && !pci_enable_ats(pdev, VTD_PAGE_SHIFT)) { > + if (!pdev->is_external && info->ats_supported && > + !pci_enable_ats(pdev, VTD_PAGE_SHIFT)) { > info->ats_enabled = 1; > domain_update_iotlb(info->domain); > info->ats_qdep = pci_ats_queue_depth(pdev); > -- > 2.19.1 >
