Re: [libvirt] [qemu RFC] qapi: add "firmware.json"

> > Hmm, I'm wondering whenever it is useful to model things this way. It's > > not like you can actually configure things for -bios seabios.rom or > > -kernel uboot.elf. Only pflash allows to actually configure things, and > > there are not that many useful combinations. The code needs > > Read+Execute. Allowing Write could be useful in theory, to allow the > > guest doing firmware updates. But I think nobody actually does that, so > > in practice it is fixed. The varstore can have different permissions, > > but it's only two useful combinations. Either allow access > > unconditionally, or allow access in secure contect (aka smm) only. > > (I hope I understand your point right:) > > I'm also fine if we simply define a fixed (but extensible) set of > mapping methods, basically a new enum type, that simply tells libvirtd > what this firmware *is*. IOW, directly reference a mapping method we > know libvirt implements, rather than give vague hints. > > This could repurpose SystemFirmwareType, but it should become more > detailed. I'm thinking like: > - ovmf: split files without requiring SMM > - ovmf_smm: split files with SMM requirement > - seabios: exactly that > - ... other things others suggest. I wouldn't name them by firmware, that is misleading. Basically we have three cases: (1) single firmware image (seabios, OVMF.fd, ...). (2) split firmware image (OVMF_{CODE,VARS}.fd), where vars can be writable unconditinally. (3) split firmware image, where access to vars should be restricted to smm mode. (2) + (3) requires pflash. (1) works with both pflash and -bios.