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I recalled an offline discussion in which he raised concern on > > > > having the kernel blindly enable ATS for cxl.cache device instead of > > > > creating a knob for admin to configure from userspace (in case > > > > security is viewed more important than functionality, upon allowing > > > > DMA to read data out of CPU caches)... > > > > > > > +CC Linux-cxl > > A cxl.cache device supporting ATS will automatically enable ATS today > > if the kernel option to enable translation is set. > > > > Even if the device is marked untrusted by the PCI layer (eg an > > external port). > > I don't follow here. The untrusted check is now in pci_ats_supported(): > > /** > * pci_ats_supported - check if the device can use ATS > * @dev: the PCI device > * > * Returns true if the device supports ATS and is allowed to use it, false > * otherwise. > */ > bool pci_ats_supported(struct pci_dev *dev) > { > if (!dev->ats_cap) > return false; > > return (dev->untrusted == 0); > } > EXPORT_SYMBOL_GPL(pci_ats_supported); > > The iommu drivers (intel/amd/arm-smmuv3) all call pci_ats_supported() > before enabling ATS on a device. Anything I missed? No, not at all, I forgot about this! Jason