On Thu, Feb 06, 2025 at 02:53:58PM +0100, Philippe Mathieu-Daudé wrote: > Hi Daniel, > > On 6/2/25 14:20, Daniel P. Berrangé wrote: > > On Thu, Feb 06, 2025 at 02:10:47PM +0100, Philippe Mathieu-Daudé wrote: > > > Introduce an abstract machine parent class which defines > > > the 'little_endian' property. Duplicate the current machine, > > > which endian is tied to the binary endianness, to one big > > > endian and a little endian machine; updating the machine > > > description. Keep the current default machine for each binary. > > > > > > 'petalogix-s3adsp1800' machine is aliased as: > > > - 'petalogix-s3adsp1800-be' on big-endian binary, > > > - 'petalogix-s3adsp1800-le' on little-endian one. > > > > Does it makes sense to expose these as different machine types ? > > > > If all the HW is identical in both cases, it feels like the > > endianness could just be a bool property of the machine type, > > rather than a new machine type. > > Our test suites expect "qemu-system-foo -M bar" to work out of > the box, we can not have non-default properties. > > (This is related to the raspberry pi discussion in > https://lore.kernel.org/qemu-devel/20250204002240.97830-1-phi...@linaro.org/). > > My plan is to deprecate 'petalogix-s3adsp1800', so once we > remove it we can merge both qemu-system-microblaze and > qemu-system-microblazeel into a single binary. > > If you don't want to add more machines, what should be the > endianness of the 'petalogix-s3adsp1800' machine in a binary > with no particular endianness? Either we add for explicit > endianness (fixing test suites) or we add one machine for > each endianness; I fail to see other options not too > confusing for our users.
We would pick an arbitrary endianness of our choosing I guess. How does this work in physical machines ? Is the choice of endianess a firmware setting, or a choice by the vendor when manufacturing in some way ? Picking an arbitrary endianess is compatible with our test suite, it just has the implication that we would only end up testing the machine in a single endianness configuration. If we wanted to test both endianness options, the test would need amending to know to try both values of the endian property on the machine. > This approach is the same I took to merge MIPS*, SH4* and > Xtensa* machines in endianness-agnostic binaries. If we have prior art like this, then remaining consistentv is desirable and thus my comments are too late. > Also the same I'm using to merge 32/64-bit targets into the > same binaries. > Assuming we have a qemu-system-x86 binary able to run i386 and > x86_64 machines, what do you expect when starting '-M pc'? How > to not confuse users wanting to run FreeDOS in 32-bit mode? > > Again, IMO having '-M pc,mode=32' is simpler, but that breaks > the test suites assumptions than machines can start with no > default values (see QOM introspection tests for example). With x86 there's no need for mode=32. Whether the machine supports 64-bit or not is a property of the CPU model chosen. eg "qemu -M pc -cpu Nehalem" would be 64-bit and "qemu -M pc -cpu pentium" would be 32-bit. The qemu-system-i386 binary is pretty much pointless as a separate thing. Libvirt will happily use qemu-system-x86_64 to run 32-bit guests, by just specifying a 32-bit CPU model With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
