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([2001:8003:e5b0:9f00:dbbc:1945:6e65:ec5]) by smtp.gmail.com with ESMTPSA id 29-20020a17090a1a5d00b0025c2c398d33sm6006386pjl.39.2023.07.30.22.07.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 30 Jul 2023 22:07:42 -0700 (PDT) Message-ID: <5f26299e-f1e0-a2ab-db83-87011fe524d5@redhat.com> Date: Mon, 31 Jul 2023 15:07:30 +1000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH v2 3/8] machine: Print supported CPU models instead of typenames Content-Language: en-US To: Igor Mammedov Cc: Richard Henderson , qemu-arm@nongnu.org, qemu-devel@nongnu.org, qemu-riscv@nongnu.org, peter.maydell@linaro.org, b.galvani@gmail.com, strahinja.p.jankovic@gmail.com, sundeep.lkml@gmail.com, kfting@nuvoton.com, wuhaotsh@google.com, nieklinnenbank@gmail.com, rad@semihalf.com, quic_llindhol@quicinc.com, marcin.juszkiewicz@linaro.org, eduardo@habkost.net, marcel.apfelbaum@gmail.com, philmd@linaro.org, wangyanan55@huawei.com, laurent@vivier.eu, vijai@behindbytes.com, palmer@dabbelt.com, alistair.francis@wdc.com, bin.meng@windriver.com, liweiwei@iscas.ac.cn, dbarboza@ventanamicro.com, zhiwei_liu@linux.alibaba.com, cohuck@redhat.com, pbonzini@redhat.com, shan.gavin@gmail.com, qemu-ppc@nongnu.org References: <20230726003205.1599788-1-gshan@redhat.com> <20230726003205.1599788-4-gshan@redhat.com> <24e54bac-9149-20da-e4cf-5829a6dcb174@linaro.org> <0454c1ad-314c-3df6-d6e9-1a05cb4c4050@redhat.com> <20230727110010.648b61a6@imammedo.users.ipa.redhat.com> From: Gavin Shan In-Reply-To: <20230727110010.648b61a6@imammedo.users.ipa.redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=gshan@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.101, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 7/27/23 19:00, Igor Mammedov wrote: > On Thu, 27 Jul 2023 15:16:18 +1000 > Gavin Shan 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. >> 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. >> >> 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-- >> 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 ' 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. > 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[]. Thanks, Gavin