Re: [libvirt PATCH V2 0/4] add loongarch support for libvirt

On Fri, Jan 12, 2024 at 02:32:43PM +0800, Xianglai Li wrote: It's really great that you're considering the entire stack, all the way up to virt-manager, while working on this! :) To clarify, loongarch support has been merged into upstream edk2 already, right? And the contents of this repository are just for convenience, since loongarch builds of edk2 have generally not made it into distros yet? I think I might have asked about this already, sorry O:-) Anyway, I fetched and installed this. The firmware descriptor looks like: { "interface-types": [ "uefi" ], "mapping": { "device": "memory", "filename": "/usr/share/edk2/loongarch64/QEMU_EFI.fd" }, "targets": [ { "architecture": "loongarch64", "machines": [ "virt", "virt-*" ] } ], "features": [ "acpi" ] } This is not what I expected: specifically, it results in libvirt generating -bios /usr/share/edk2/loongarch64/QEMU_EFI.fd So only one of the two files is used, in read-only mode, and there is no persistent NVRAM storage that the guest can use. This is what I expected instead: { "interface-types": [ "uefi" ], "mapping": { "device": "flash", "mode": "split", "executable": { "filename": "/usr/share/edk2/loongarch64/QEMU_EFI.fd", "format": "raw" }, "nvram-template": { "filename": "/usr/share/edk2/loongarch64/QEMU_VARS.fd", "format": "raw" } }, "targets": [ { "architecture": "loongarch64", "machines": [ "virt", "virt-*" ] } ], "features": [ "acpi" ] } I've tried installing such a descriptor and libvirt picks it up, resulting in the following guest configuration: <os firmware='efi'> <type arch='loongarch64' machine='virt'>hvm</type> <firmware> <feature enabled='no' name='enrolled-keys'/> <feature enabled='no' name='secure-boot'/> </firmware> <loader readonly='yes' type='pflash'>/usr/share/edk2/loongarch64/QEMU_EFI.fd</loader> <nvram template='/usr/share/edk2/loongarch64/QEMU_VARS.fd'>/var/lib/libvirt/qemu/nvram/guest_VARS.fd</nvram> <boot dev='hd'/> </os> which in turn produces the following QEMU command line options: -blockdev '{"driver":"file","filename":"/usr/share/edk2/loongarch64/QEMU_EFI.fd","node-name":"libvirt-pflash0-storage","auto-read-only":true,"discard":"unmap"}' -blockdev '{"node-name":"libvirt-pflash0-format","read-only":true,"driver":"raw","file":"libvirt-pflash0-storage"}' -blockdev '{"driver":"file","filename":"/var/lib/libvirt/qemu/nvram/guest_VARS.fd","node-name":"libvirt-pflash1-storage","auto-read-only":true,"discard":"unmap"}' -blockdev '{"node-name":"libvirt-pflash1-format","read-only":false,"driver":"raw","file":"libvirt-pflash1-storage"}' Unfortunately, with this configuration the guest fails to start: qemu-system-loongarch64: Property 'virt-machine.pflash0' not found This error message looked familiar to me, as it is the same that I hit when trying out UEFI support on RISC-V roughly a year ago[1]. In this case, however, it seems that the issue runs deeper: it's not just that the flash devices are not wired up to work as blockdevs, but even the old -drive syntax doesn't work. Looking at the QEMU code, it appears that the loongarch/virt machine only creates a single pflash device and exposes it via -bios. So it seems that there is simply no way to achieve the configuration that we want. I think that this is something that needs to be addressed as soon as possible. In the long run, guest-accessible NVRAM storage is a must, and I'm not sure it would make a lot of sense to merge loongarch support into libvirt until the firmware situation has been sorted out in the lower layers. Regardless of what I said above, this actually worked quite well! I was able to boot the MATE image and, ignoring the expected slowness caused by emulation, things were generally fairly smooth. Note that I tried the LXDE image first, expecting it to be a bit smaller and faster, but in that case I wasn't able to get a successful boot: edk2 loaded up just fine, but the guest OS was never started and I was dropped into the edk2 shell instead. Maybe that's a known issue, but I thought I'd point it out. [1] https://lists.gnu.org/archive/html/qemu-devel/2023-05/msg06258.html -- Andrea Bolognani / Red Hat / Virtualization