On Mon, Jun 15, 2020 at 5:45 AM Bruce Ashfield <[email protected]> wrote: > On Mon, Jun 15, 2020 at 5:11 AM Christopher Clark > <[email protected]> wrote: > > > > On Fri, Jun 5, 2020 at 5:58 PM Corey Minyard <[email protected]> wrote: > > > > > > On Fri, Jun 05, 2020 at 07:53:53PM -0400, Bruce Ashfield wrote: > > > > On Fri, Jun 5, 2020 at 5:16 PM Corey Minyard <[email protected]> > > > > wrote: > > > > > > > > > > On Fri, Jun 05, 2020 at 07:55:37PM +0000, Stewart Hildebrand wrote: > > > > > > + Corey > > > > > > > > > > > > On Friday, June 5, 2020 3:19 PM, Bruce Ashfield wrote: > > > > > > >On Fri, Jun 5, 2020 at 3:12 PM Stewart Hildebrand wrote:
> > > > > > Corey: you are hereby encouraged to submit patches to > > > > > > meta-virtualization. > > > > > > > > > > Ok. The layer has the following basic pieces: > > > > Before we get to the other pieces, I'd like to cover the new "rpixen" > > MACHINE type that the layer introduces. > > > > My preference is for avoiding introduction of another MACHINE to > > reconfigure an existing one to run Xen, if possible, and use the > > existing "raspberrypi4-64". I'm hoping to avoid the pattern of > > creating a new machine for Xen for each board that we add support for. > > In meta-virtualization, there's the "xen" DISTRO_FEATURE, which is > > used to turn on Xen-specific functionality and compatibility, and I'd > > like to explore whether that can be made to be sufficient to enable > > what is needed. > > > > To that end, I've done an initial pass to see what it might take and > > the work-in-progress from that is posted here: > > https://github.com/dozylynx/meta-virtualization/tree/raspberry-pi4-initial-xen > > > > Some minor changes to other layers could assist - eg. to remove the > > need for a guest filesystem to contain the hypervisor binary - and > > there's still some tidying to do. > > > > > > > 1 The xen patches for the Pi4, just a few patches. As the Xen group > > > > > fixes things, I keep adding :). > > > > Unfortunately I had to drop these patches from my local test to get it > > to boot. It could easily be a local build issue or a fault with the > > one test I've run so far, but I did have success booting with just Xen > > 4.13 and I'd like to get a bit more understanding and confidence in > > them before we bring them in. > > > > > > > 2 Hacks for getting the Pi4 kernel config right for xen. This should > > > > > go > > > > > away if you don't use the kernel from the Pi4 yocto layer, as it > > > > > doesn't work like most kernels in yocto. > > > > > > > > I should take a look at the configs and see if I can create a fragment > > > > or two, but I can take care of that. > > > > > > That shouldn't be necessary. The standard fragments work, it's just > > > that the Pi kernel does not use them. So this is really Pi+Xen > > > specific, and hopefully they can fix the Pi kernel to use the normal > > > fragments in the future. > > > > The linux-raspberrypi kernel does use linux-yocto; it's just that > > meta-virtualization > > needs a matching .inc file to be present for the kernel version that > > you're using. > > Assuming you're using Linux 4.19 (which is what I've tested with) add this > > file: > > > > meta-virtualization/recipes-kernel/linux/linux-yocto_4.19_virtualization.inc > > containing just: > > include linux-yocto_virtualization.inc > > which will then enable the linux-raspberrypi kernel to add the > > meta-virt Xen fragment. > > > > There are also two Linux patches: > > 1) Disable DMA in the SDHCI driver > > This one needs more information in the commit text to understand what > > is motivating doing this and what the effects of it are. Should it go > > into the standard Raspberry Pi kernel? > > 2) Fix PCIe in dom0 for RPi4 > > Is this fixed upstream in more recent kernels? It would be good to > > have a pointer to that if so. > > > > Bruce: To apply these to just the Raspberry Pi kernel when it's being > > used with Xen, a kernel bbappend in a raspberrypi dynamic-layers might > > be an option to consider - eg: > > https://github.com/dozylynx/meta-virtualization/tree/raspberry-pi4-initial-xen/dynamic-layers/raspberrypi/recipes-kernel/linux > > I can most likely live with that. I obviously make sure that the > reference linux-yocto kernel doesn't need anything to work out of the > box, but we can't (and shouldn't) enforce that choice on everyone. I'd > rather have patches centralized in a topic layer like > meta-virtualization, so if we need to add a dynamic layer and a few > patches, that's a good place to be. please see my new comment below. > > > > > 5 A few Pi-specific hacks for config and u-boot. > > > > > > > > #5 does sound like BSP stuff. Is any of it destined for the rpi layers > > > > ? Or is it both rpi AND xen specific, so doesn't really make sense > > > > there either ? > > > > > > It's both Pi and Xen specific. If everything gets put where it should > > > be, that would be the only thing left in this layer :). > > > > These are in recipes-bsp and I agree that they're both Pi and Xen > > specific. I think these are small enough pieces that keeping them in > > meta-virtualization could be a reasonable call, since that's the layer > > where Xen support is focussed, and so they can be added to: > > dynamic-layers/raspberrypi/recipes-bsp > > which indicates their status as amendments to the meta-raspberrypi > > layer. Changes to them would then be easily coordinated with the Xen > > recipes. > > Agreed. Since I wrote this, we've seen some expressed interest in support for running Xen on the NVIDIA Jetson Nano and Xavier NX boards, and on the xen-devel mailing list, a report of success running Xen on the RockPro64 board: https://lists.xenproject.org/archives/html/xen-devel/2020-06/msg01067.html I've personally built Xen with meta-virtualization to run on the Cubietruck for development and testing; the Odroid C2 and XU4 are of interest, as is the Xilinx Ultra-96-V2 board; and the NVidia Jetson TX1 at one point had some non-upstream patches available to enable Xen on it. PCEngines maintains Xen compatibility for their APU2 in meta-pcengines. There are also some challenges being encountered in getting a more recent Linux kernel working as a dom0 on the Raspberry Pi 4 - eg. the Linux Foundation Eve Project run their own patches for 5.6 here: https://github.com/lf-edge/eve/tree/master/pkg/new-kernel/patches-5.6.x All of this points towards it being a reasonable proposition to have a dedicated Xen hardware support Yocto layer, so that board-specific tweaks for hardware compatibility with Xen can be maintained without complicating meta-virtualization, while continuing to pool Xen-aware contributions in a centralized layer. I'd like to propose creating: 'meta-xen-bsp'; and I'm willing to work on maintaining it. Feedback to this suggestion is welcome. Bruce: how does this sound to you? Christopher
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