On Wed, 30 Aug 2023 17:34:12 +1000 Gavin Shan <[email protected]> wrote:
> Hi Igor, > > On 8/29/23 19:03, Igor Mammedov wrote: > > On Tue, 29 Aug 2023 16:28:45 +1000 > > Gavin Shan <[email protected]> wrote: > >> On 8/29/23 00:46, Igor Mammedov wrote: > >>> On Mon, 31 Jul 2023 15:07:30 +1000 > >>> Gavin Shan <[email protected]> wrote: > >>>> On 7/27/23 19:00, Igor Mammedov wrote: > >>>>> On Thu, 27 Jul 2023 15:16:18 +1000 > >>>>> Gavin Shan <[email protected]> wrote: > >>>>> > >>>>>> On 7/27/23 09:08, Richard Henderson wrote: > >>>>>>> On 7/25/23 17:32, Gavin Shan wrote: > >>>>>>>> -static const char *q800_machine_valid_cpu_types[] = { > >>>>>>>> +static const char * const q800_machine_valid_cpu_types[] = { > >>>>>>>> M68K_CPU_TYPE_NAME("m68040"), > >>>>>>>> NULL > >>>>>>>> }; > >>>>>>>> +static const char * const q800_machine_valid_cpu_models[] = { > >>>>>>>> + "m68040", > >>>>>>>> + NULL > >>>>>>>> +}; > >>>>>>> > >>>>>>> I really don't like this replication. > >>>>>>> > >>>>>> > >>>>>> Right, it's going to be lots of replications, but gives much > >>>>>> flexibility. > >>>>>> There are 21 targets and we don't have fixed pattern for the mapping > >>>>>> between > >>>>>> CPU model name and CPU typename. I'm summarizing the used patterns > >>>>>> like below. > >>>>>> > >>>>>> 1 All CPU model names are mappinged to fixed CPU typename; > >>>>> > >>>>> plainly spelled it would be: cpu_model name ignored and > >>>>> a cpu type is returned anyways. > >>>>> > >>>>> I'd make this hard error right away, as "junk in => error out" > >>>>> it's clearly user error. I think we don't even have to follow > >>>>> deprecation process for that. > >>>>> > >>>> > >>>> Right, It's not expected behavior to map ambiguous CPU model names to > >>>> the fixed CPU typename. > >>> > >>> to be nice we can deprecate those and then later remove. > >>> (while deprecating make those targets accept typenames) > >>> > >> > >> Lets put it aside for now and revisit it later, so that we can focus on > >> the conversion from the CPU type name to the CPU model name for now. > >> > >>>> > >>>>>> 2 CPU model name is same to CPU typename; > >>>>>> 3 CPU model name is alias to CPU typename; > >>>>>> 4 CPU model name is prefix of CPU typename; > >>>>> > >>>>> and some more: > >>>>> 5. cpu model names aren't names at all sometimes, and some other > >>>>> CPU property is used. (ppc) > >>>>> This one I'd prefer to get rid of and ppc handling more consistent > >>>>> with other targets, which would need PPC folks to persuaded to drop > >>>>> PVR lookup. > >>>>> > >>>> > >>>> I put this into class 3, meaning the PVRs are regarded as aliases to CPU > >>>> typenames. > >>> > >>> with PPC using 'true' aliases, -cpu input is lost after it's translated > >>> into typename. > >>> (same for alpha) > >>> > >>> it also adds an extra fun with 'max' cpu model but that boils down to > >>> above statement. > >>> (same for > >>> * sh4 > >>> * cris(in user mode only, but you are making sysemu extension, so it > >>> doesn't count) > >>> ) > >>> For this class of aliases reverse translation won't yield the same > >>> result as used -cpu. The only option you have is to store -cpu cpu_model > >>> somewhere (use qemu_opts??, and then fetch it later to print in error > >>> message) > >>> > >>> x86 has 'aliases' as well, but in reality it creates distinct cpu types > >>> for each 'alias', so it's possible to do reverse translation. > >>> > >> > >> It's true that '-cpu input' gets lost in these cases. However, the CPU type > >> name instead of the CPU model name is printed in the error message when the > >> CPU type is validated in hw/core/machine.c::machine_run_board_init(). It > >> looks > >> good to me to print the CPU type name instead of the model name there. > > > > It's the same confusing whether it's type or cpumodel it it doesn't match > > user provided value. > > > > I tend to agree that it's misleading to print the CPU type name in the > error message in hw/core/machine.c::machine_run_board_init(), where the CPU > type is validated. qemu_opts may be too heavy for this. It eventually turns > to a machine's property if @machine_opts_dict is the best place to store > '-cpu input'. Besides, it doesn't fit for another case very well, where > current_machine->cpu_type = machine_class->default_cpu_type if '-cpu input' > isn't provided by user. > > For simplicity, how about to add MachineState::cpu_model? It's initialized to > cpu_model_from_type(machine_class->default_cpu_type) in qemu_init(), or > g_strdump(model_pieces[0) in parse_cpu_option(). I'd prefer not bringing cpu_model back to device models (Machine in this case) after getting rid of it. > >> Another error message is printed when the CPU model specified in '-cpu > >> input' > >> isn't valid. The CPU model has been printed and it looks good either. > >> > >> # qemu-system-aarch64 -M virt -cpu aaa > >> qemu-system-aarch64: unable to find CPU model 'aaa' > >> > >> Are there other cases I missed where we need to print the CPU model name, > >> which > >> is specified by user through '-cpu input'? > >> > >>>>>> > >>>>>> Target Categories suffix-of-CPU-typename > >>>>>> ------------------------------------------------------- > >>>>>> alpha -234 -alpha-cpu > >>>>>> arm ---4 -arm-cpu > >>>>>> avr -2-- > >>>>>> cris --34 -cris-cpu > >>>>>> hexagon ---4 -hexagon-cpu > >>>>>> hppa 1--- > >>>>>> i386 ---4 -i386-cpu > >>>>>> loongarch -2-4 -loongarch-cpu > >>>>>> m68k ---4 -m68k-cpu > >>>>>> microblaze 1--- > >>>>>> mips ---4 -mips64-cpu -mips-cpu > >>>>>> nios2 1--- > >>>>>> openrisc ---4 -or1k-cpu > >>>>>> ppc --34 -powerpc64-cpu -powerpc-cpu > >>>>>> riscv ---4 -riscv-cpu > >>>>>> rx -2-4 -rx-cpu > >>>>>> s390x ---4 -s390x-cpu > >>>>>> sh4 --34 -superh-cpu > >>>>>> sparc -2-- > >>> > >>> it's case 4 > >>> > >> > >> Yes. > >> > >>>>>> tricore ---4 -tricore-cpu > >>>>>> xtensa ---4 -xtensa-cpu > >>>>>> > >>>>>> There are several options as below. Please let me know which one or > >>>>>> something > >>>>>> else is the best. > >>>>>> > >>>>>> (a) Keep what we have and use mc->valid_{cpu_types, cpu_models}[] to > >>>>>> track > >>>>>> the valid CPU typenames and CPU model names. > >>>>>> > >>>>>> (b) Introduce CPUClass::model_name_by_typename(). Every target has > >>>>>> their own > >>>>>> implementation to convert CPU typename to CPU model name. The CPU > >>>>>> model name > >>>>>> is parsed from mc->valid_cpu_types[i]. > >>>>>> > >>>>>> char *CPUClass::model_by_typename(const char *typename); > >>>>>> > >>>>>> (c) As we discussed before, use mc->valid_cpu_type_suffix and > >>>>>> mc->valid_cpu_models > >>>>>> because the CPU type check is currently needed by target > >>>>>> arm/m68k/riscv where we > >>>>>> do have fixed pattern to convert CPU model names to CPU typenames. The > >>>>>> CPU typename > >>>>>> is comprised of CPU model name and suffix. However, it won't be > >>>>>> working when the CPU > >>>>>> type check is required by other target where we have patterns other > >>>>>> than this. > >>>>> > >>>>> none of above is really good, that's why I was objecting to introducing > >>>>> reverse type->name mapping. That ends up with increased amount junk, > >>>>> and it's not because your patches are bad, but because you are trying > >>>>> to deal with cpu model names (which is a historically evolved mess). > >>>>> The best from engineering POV would be replacing CPU models with > >>>>> type names. > >>>>> > >>>>> Even though it's a bit radical, I very much prefer replacing > >>>>> cpu_model names with '-cpu type'usage directly. Making it > >>>>> consistent with -device/other interfaces and coincidentally that > >>>>> obsoletes need in reverse name mapping. > >>>>> > >>>>> It's painful for end users who will need to change configs/scripts, > >>>>> but it's one time job. Additionally from QEMU pov, codebase > >>>>> will be less messy => more maintainable which benefits not only > >>>>> developers but end-users in the end. > >>>>> > >>>> > >>>> I have to clarify the type->model mapping has been existing since the > >>>> model->type mapping was introduced with the help of CPU_RESOLVING_TYPE. > >>>> I mean the logic has been existing since the existence of > >>>> CPU_RESOLVING_TYPE, > >>>> even the code wasn't there. > >>>> > >>>> I'm not sure about the idea to switch to '-cpu <cpu-type-name>' since > >>>> it was rejected by Peter Maydell before. Hope Peter can double confirm > >>>> for this. For me, the shorter name is beneficial. For example, users > >>>> needn't to have '-cpu host-arm-cpu' for '-cpu host'. > >>>> > >>>> > >>>>> [rant: > >>>>> It's the same story repeating over and over, when it comes to > >>>>> changing QEMU CLI, which hits resistance wall. But with QEMU > >>>>> deprecation process we've changed CLI behavior before, > >>>>> despite of that world didn't cease to exist and users > >>>>> have adapted to new QEMU and arguably QEMU became a tiny > >>>>> bit more maintainable since we don't have to deal some > >>>>> legacy behavior. > >>>>> ] > >>>>> > >>>> > >>>> I need more context about 'deprecation process' here. My understanding > >>>> is both CPU typename and model name will be accepted for a fixed period > >>>> of time. However, a warning message will be given to indicate that the > >>>> model name will be obsoleted soon. Eventually, we switch to CPU typename > >>>> completely. Please correct me if there are anything wrong. > >>> > >>> yep, that's the gist of deprecation in this case. > >>> > >> > >> Ok. Thanks for your confirm. > >> > >>>>> Another idea back in the days was (as a compromise), > >>>>> 1. keep using keep valid_cpu_types > >>>>> 2. instead of introducing yet another way to do reverse mapping, > >>>>> clean/generalize/make it work everywhere list_cpus (which > >>>>> already does that mapping) and then use that to do your thing. > >>>>> It will have drawbacks you've listed above, but hopefully > >>>>> that will clean up and reuse existing list_cpus. > >>>>> (only this time, I'd build it around query-cpu-model-expansion, > >>>>> which output is used by generic list_cpus) > >>>>> [and here I'm asking to rewrite directly unrelated QEMU part yet > >>>>> again] > >>>>> > >>>> > >>>> I'm afraid that list_cpus() is hard to be reused. All available CPU > >>>> model names > >>>> are listed by list_cpus(). mc->valid_cpu_types[] are just part of them > >>>> and variable > >>>> on basis of boards. Generally speaking, we need a function to do reverse > >>>> things > >>>> as to CPUClass::class_by_name(). So I would suggest to introduce > >>>> CPUClass::model_from_type(), > >>>> as below. Could you please suggest if it sounds reasonable to you? > >>>> > >>>> - CPUClass::class_by_name() is modified to > >>>> char *CPUClass::model_to_type(const char *model) > >>>> > >>>> - char *CPUClass::type_to_model(const char *type) > >>>> > >>>> - CPUClass::type_to_model() is used in cpu_list() for every target when > >>>> CPU > >>>> model name, fetched from CPU type name, is printed in > >>>> xxx_cpu_list_entry() > >>>> > >>>> - CPUClass::type_to_model() is reused in hw/core/machine.c to get the CPU > >>>> model name from CPU type names in mc->valid_cpu_types[]. > >>> > >>> instead of per target hooks (which are atm mostly open-coded in several > >>> places) > >>> how about adding generic handler for cases 2,4: > >>> cpu_type_to_model(typename) > >>> cpu_suffix = re'-*-cpu' > >>> if (class_exists(typename - cpu_suffix)) > >>> return typename - cpu_suffix > >>> else if (class_exists(typename)) > >>> return typename > >>> explode > >>> > >>> that should work for translating valid_cpus typenames to cpumodel names > >>> and once that in place cleanup all open-coded translations with it > >>> tree-wide > >>> > >>> you can find those easily by: > >>> git grep _CPU_TYPE_SUFFIX > >>> git grep query_cpu_definitions > >>> > >> > >> Thanks for the advice. I think it's enough for now since the CPU type > >> invalidation is currently done for arm/mips/riscv for now. On these > >> targets, the CPU type name is always the combination of the CPU model > >> name and suffix. I will add helper qemu/cpu.c::cpu_model_by_name() > > > > cpu_model_from_type() would be describe what function does better. > > > > Agreed, thanks. > > >> as you suggested. Note that, the suffix can be gained by ("-" > >> CPU_RESOLVING_TYPE) > >> > >> Yes, the newly added helper cpu_model_by_name() needs to be applied > >> to targets where query_cpu_definitions and cpu_list are defined. > > Thanks, > Gavin >
