Re: [PATCH RFCv1 1/3] PCI: Allow ATS to be always on for CXL.cache capable devices
From: Jason Gunthorpe <jgg@nvidia.com>
Date: 2026-02-19 17:41:45
Also in:
linux-cxl, linux-iommu, linux-pci, lkml
On Thu, Feb 19, 2026 at 08:53:19AM -0800, Nicolin Chen wrote:
The thing is that those driver_managed_dma callbacks don't call iommu_device_use_default_domain(). So, the iommu core loses the trigger to switch domain from BLOCKED/empty-DMA to DMA/IDENTITY.
But they don't use DMA API at all so it doesn't matter to them. Your issue is that BLOCKED breaks MSI on ARM. That is fixed by using an empty-DMA API domain as default. What is missing is to bring back the IDENTITY performance optimization in a secure way. Jason