On Wed, 19 Jan 2022, Oleksii Moisieiev wrote: > On Fri, Dec 24, 2021 at 02:30:50PM +0100, Julien Grall wrote: > > Hi, > > > > On 23/12/2021 20:06, Stefano Stabellini wrote: > > > On Wed, 22 Dec 2021, Stefano Stabellini wrote: > > > > # Future Ideas > > > > > > > > A great suggestion by Julien is to start supporting the dom0less partial > > > > device tree format in xl/libxl as well so that we can have a single > > > > "device_tree" option in dom.cfg instead of 4 (device_tree, iomem, irqs, > > > > dtdev). > > > > > > > > Even with that implemented, the user has still to provide a partial dtb, > > > > xen,reg and xen,path. I think this is a great step forward and we should > > > > do that, if nothing else to make it easier to switch between dom0less > > > > and normal domU configurations. But the number of options and > > > > information that the user has to provide is still similar to what we > > > > have today. > > > > > > I have just realized that if we start to parse the partial DTB in > > > xl/libxl the same way that we do for dom0less guests (parse "xen,path", > > > "xen,reg", and "interrupts", making dtdev, irqs and iomem optional) > > > actually we can achieve the goal below thanks to the combination: > > > "xen,path" + "xen,force-assign-without-iommu". > > > > > > In other words, with dom0less we already have a way to specify the link > > > to the host node even if the device is not a DMA master. We can do that > > > by specifying both xen,path and xen,force-assign-without-iommu for a > > > device. > > > > > > This is just FYI. I am not suggesting we should introduce dom0less-style > > > partial DTBs in order to get SCMI support in guests (although it would > > > be great to have). I think the best way forward for this series is one > > > of the combinations below, like a) + d), or a) + c) > > > > I strongly prefer a) + c) because a warning is easy to miss/ignore. At least > > with the extra property the user made an action to think about it and agree > > that this is the way do it. > > > > It is also easier to spot if we ask the user to provide the configuration > > file. > > > > Let me share my thoughts about c), which is: > c) require force-assign-without-iommu="true" in dom.cfg > > Adding this parameter to domain config means removing > xen,force-assign-without-iommu param from partial DTB.
Why? No I don't think so. > This will affect dom0less configuration, which I can't test for now > without extra effort. We are just talking about adding: force-assign-without-iommu="true" to the xl config file. For instance: dtdev = [ "/amba/serial@ff000000" ] iomem = ["0xff000,1"] force-assign-without-iommu="true" It is unrelated to the dom0less partial DTB. There is no need to test dom0less to do this.
