On Tue, Apr 01, 2025 at 11:35:19AM +0100, Jean-Philippe Brucker wrote: > On Fri, Mar 28, 2025 at 10:11:13AM +0100, Joel Granados wrote: > > Custom qemu device: pci-ats-testdev > > ------------------------------------- > > To support IOMMU testing under qemu, the pci-ats-testdev [10] > > (different from pci-testdev [11]) was used to emulate DMA transactions. > > It is a full fledged pci device capable of executing emulated DMA > > accesses. It was originally intended to test Linux kernel interactions > > with devices that had a working Address Translation Cache (ATC) but can > > become a platform capable of testing anything PCI/IOMMU related if > > needed. > > Yes please! Maybe "pcie-testdev" rather than "pci-ats-testdev"? There Definitely. If it is a more general pcie test framework, we need to change the name to something like that; agreed. > are other PCIe features that are poorly tested at the moment, for example > PASID and PRI. The programming model of devices that actually implement Actually, PRI was what we used it for. I have this as one of the potential next steps for iommutests. > those can get too complex so we need something simpler to precisely stress > the IOMMU driver infrastructure. Driver unit-tests alone aren't good > enough for exercising TLB invalidation (DMA after removing a mapping must > crash), tricky cleanup paths (eg. killing a process bound to a device > that's issuing page requests), runtime PM, MSIs etc. I'm guessing testing Totally agree. PRI is tricky to test indeed. > newer/future features like TDISP would also benefit from a simple device. > > Some time back I needed a device like that to reproduce some tricky races > but never got round to implementing extra PCIe features. Although this one > [1] is based on virtio any programming interface should work as long as it > can instruct the device to send precise DMA transactions, ideally many in > parallel. And it can be up-streamed to QEMU if it ends up being used for linux kernel testing. Best -- Joel Granados
