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Tsirkin" To: Ani Sinha Cc: Sergio Lopez , Paolo Bonzini , Richard Henderson , Eduardo Habkost , Marcel Apfelbaum , Zhao Liu , imammedo@redhat.com, qemu-devel@nongnu.org Subject: Re: [PATCH v7] hw/i386/cpu: remove default_cpu_version and simplify Message-ID: <20250511093927-mutt-send-email-mst@kernel.org> References: <20250307102329.556260-1-anisinha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250307102329.556260-1-anisinha@redhat.com> Received-SPF: pass client-ip=170.10.133.124; envelope-from=mst@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -46 X-Spam_score: -4.7 X-Spam_bar: ---- X-Spam_report: (-4.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.587, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=-1, RCVD_IN_MSPIKE_WL=-0.01, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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 Fri, Mar 07, 2025 at 03:53:28PM +0530, Ani Sinha wrote: > commit 0788a56bd1ae3 ("i386: Make unversioned CPU models be aliases") > introduced 'default_cpu_version' for PCMachineClass. This created three > categories of CPU models: > - Most unversioned CPU models would use version 1 by default. > - For machines 4.0.1 and older that do not support cpu model aliases, a > special default_cpu_version value of CPU_VERSION_LEGACY is used. > - It was thought that future machines would use the latest value of cpu > versions corresponding to default_cpu_version value of > CPU_VERSION_LATEST [1]. > > All pc machines still use the default cpu version of 1 for > unversioned cpu models. Use of CPU_VERSION_LATEST was removed in [2]. > > This change cleans up the complicated logic around default_cpu_version > including getting rid of default_cpu_version property itself. One new > flag is introduced for the legacy model for machines 4.0.1 and older. > For older machines, a new pc machine property is > introduced that separates pc machine versions 4.0.1 and older from the newer > machines. 4.0.1 and older machines are scheduled to be deleted towards > end of 2025 since they would be 6 years old by then. At that time, we can > remove all logic around legacy cpus. > This change also removes all complications around CPU_VERSION_AUTO > including removal of the value itself. > > 1) See commit dcafd1ef0af227 ("i386: Register versioned CPU models") > 2) See commit XXX ("microvm: do not use the lastest cpu version") > > CC: imammedo@redhat.com > Signed-off-by: Ani Sinha > Reviewed-by: Zhao Liu Anyone merging this? If so: Reviewed-by: Michael S. Tsirkin > --- > hw/i386/microvm.c | 2 +- > hw/i386/pc.c | 1 + > hw/i386/pc_piix.c | 10 +++++--- > hw/i386/pc_q35.c | 10 +++++--- > hw/i386/x86-common.c | 4 +--- > include/hw/i386/pc.h | 6 ++--- > include/hw/i386/x86.h | 2 +- > target/i386/cpu.c | 56 ++++++++++++------------------------------- > target/i386/cpu.h | 16 +------------ > 9 files changed, 37 insertions(+), 70 deletions(-) > > changelog: > v2: explain in commit log why use of CPU_VERSION_LATEST for machines > is problematic. > v3: fix a bug that broke the pipeline > https://gitlab.com/mstredhat/qemu/-/pipelines/1626171267 > when cpu versions are explicitly specified in the command line, > respect that and do not enforce legacy (unversioned) cpu logic. > The pipeline is green now with the fix: > https://gitlab.com/anisinha/qemu/-/pipelines/1626783632 > v4: made changes as per Zhao's suggestions. > Pipeline passes https://gitlab.com/anisinha/qemu/-/pipelines/1635829877 > v5: adjustment of pc_init_cpus() declaration as per Zhao's suggestion. This > simplifies things and also passes compilation. > CI still passes https://gitlab.com/anisinha/qemu/-/pipelines/1637657451 > v6: cosmetic commit log correction as suggested by Igor. rebase, added tags. > v7: This patch is based off the top of > https://mail.gnu.org/archive/html/qemu-devel/2025-03/msg00934.html. > Igor's inputs taken into consideration. > CI passed. > Note: The above patch has not merged to QEMU upstream yet. Hence, its > commit hash is marked as XXX in the commit log for this patch. > > diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c > index a340a5fd39..0eca629958 100644 > --- a/hw/i386/microvm.c > +++ b/hw/i386/microvm.c > @@ -491,7 +491,7 @@ static void microvm_machine_state_init(MachineState *machine) > > microvm_memory_init(mms); > > - x86_cpus_init(x86ms, 1); > + x86_cpus_init(x86ms); > > microvm_devices_init(mms); > } > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index 63a96cd23f..6a2ccfd42a 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -30,6 +30,7 @@ > #include "hw/hyperv/hv-balloon.h" > #include "hw/i386/fw_cfg.h" > #include "hw/i386/vmport.h" > +#include "target/i386/cpu.h" > #include "system/cpus.h" > #include "hw/ide/ide-bus.h" > #include "hw/timer/hpet.h" > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c > index 04d2957adc..b793a4c765 100644 > --- a/hw/i386/pc_piix.c > +++ b/hw/i386/pc_piix.c > @@ -181,7 +181,12 @@ static void pc_init1(MachineState *machine, const char *pci_type) > } > > pc_machine_init_sgx_epc(pcms); > - x86_cpus_init(x86ms, pcmc->default_cpu_version); > + > + if (pcmc->no_versioned_cpu_model) { > + /* use legacy cpu as it does not support versions */ > + x86_cpu_set_legacy_version(); > + } > + x86_cpus_init(x86ms); > > if (kvm_enabled()) { > kvmclock_create(pcmc->kvmclock_create_always); > @@ -457,7 +462,6 @@ static void pc_i440fx_machine_options(MachineClass *m) > ObjectClass *oc = OBJECT_CLASS(m); > pcmc->default_south_bridge = TYPE_PIIX3_DEVICE; > pcmc->pci_root_uid = 0; > - pcmc->default_cpu_version = 1; > > m->family = "pc_piix"; > m->desc = "Standard PC (i440FX + PIIX, 1996)"; > @@ -669,7 +673,7 @@ static void pc_i440fx_machine_4_0_options(MachineClass *m) > { > PCMachineClass *pcmc = PC_MACHINE_CLASS(m); > pc_i440fx_machine_4_1_options(m); > - pcmc->default_cpu_version = CPU_VERSION_LEGACY; > + pcmc->no_versioned_cpu_model = true; > compat_props_add(m->compat_props, hw_compat_4_0, hw_compat_4_0_len); > compat_props_add(m->compat_props, pc_compat_4_0, pc_compat_4_0_len); > } > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c > index 77536dd697..be7775e9de 100644 > --- a/hw/i386/pc_q35.c > +++ b/hw/i386/pc_q35.c > @@ -187,7 +187,12 @@ static void pc_q35_init(MachineState *machine) > } > > pc_machine_init_sgx_epc(pcms); > - x86_cpus_init(x86ms, pcmc->default_cpu_version); > + > + if (pcmc->no_versioned_cpu_model) { > + /* use legacy cpu as it does not support versions */ > + x86_cpu_set_legacy_version(); > + } > + x86_cpus_init(x86ms); > > if (kvm_enabled()) { > kvmclock_create(pcmc->kvmclock_create_always); > @@ -339,7 +344,6 @@ static void pc_q35_machine_options(MachineClass *m) > { > PCMachineClass *pcmc = PC_MACHINE_CLASS(m); > pcmc->pci_root_uid = 0; > - pcmc->default_cpu_version = 1; > > m->family = "pc_q35"; > m->desc = "Standard PC (Q35 + ICH9, 2009)"; > @@ -547,7 +551,7 @@ static void pc_q35_machine_4_0_1_options(MachineClass *m) > { > PCMachineClass *pcmc = PC_MACHINE_CLASS(m); > pc_q35_machine_4_1_options(m); > - pcmc->default_cpu_version = CPU_VERSION_LEGACY; > + pcmc->no_versioned_cpu_model = true; > /* > * This is the default machine for the 4.0-stable branch. It is basically > * a 4.0 that doesn't use split irqchip by default. It MUST hence apply the > diff --git a/hw/i386/x86-common.c b/hw/i386/x86-common.c > index 1b0671c523..e8c827c1da 100644 > --- a/hw/i386/x86-common.c > +++ b/hw/i386/x86-common.c > @@ -66,15 +66,13 @@ out: > object_unref(cpu); > } > > -void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version) > +void x86_cpus_init(X86MachineState *x86ms) > { > int i; > const CPUArchIdList *possible_cpus; > MachineState *ms = MACHINE(x86ms); > MachineClass *mc = MACHINE_GET_CLASS(x86ms); > > - x86_cpu_set_default_version(default_cpu_version); > - > /* > * Calculates the limit to CPU APIC ID values > * > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h > index 103b54301f..477960275e 100644 > --- a/include/hw/i386/pc.h > +++ b/include/hw/i386/pc.h > @@ -92,9 +92,6 @@ struct PCMachineClass { > > /* Compat options: */ > > - /* Default CPU model version. See x86_cpu_set_default_version(). */ > - int default_cpu_version; > - > /* ACPI compat: */ > bool has_acpi_build; > int pci_root_uid; > @@ -125,6 +122,9 @@ struct PCMachineClass { > * check for memory. > */ > bool broken_32bit_mem_addr_check; > + > + /* whether the machine supports versioned cpu models */ > + bool no_versioned_cpu_model; > }; > > #define TYPE_PC_MACHINE "generic-pc-machine" > diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h > index d43cb3908e..2d2b987fa1 100644 > --- a/include/hw/i386/x86.h > +++ b/include/hw/i386/x86.h > @@ -114,7 +114,7 @@ void init_topo_info(X86CPUTopoInfo *topo_info, const X86MachineState *x86ms); > uint32_t x86_cpu_apic_id_from_index(X86MachineState *x86ms, > unsigned int cpu_index); > > -void x86_cpus_init(X86MachineState *pcms, int default_cpu_version); > +void x86_cpus_init(X86MachineState *pcms); > void x86_rtc_set_cpus_count(ISADevice *rtc, uint16_t cpus_count); > void x86_cpu_pre_plug(HotplugHandler *hotplug_dev, > DeviceState *dev, Error **errp); > diff --git a/target/i386/cpu.c b/target/i386/cpu.c > index 2da2cf36fd..e5c8dd98d0 100644 > --- a/target/i386/cpu.c > +++ b/target/i386/cpu.c > @@ -5624,30 +5624,16 @@ static const X86CPUDefinition builtin_x86_defs[] = { > }, > }; > > -/* > - * We resolve CPU model aliases using -v1 when using "-machine > - * none", but this is just for compatibility while libvirt isn't > - * adapted to resolve CPU model versions before creating VMs. > - * See "Runnability guarantee of CPU models" at > - * docs/about/deprecated.rst. > - */ > -X86CPUVersion default_cpu_version = 1; > - > -void x86_cpu_set_default_version(X86CPUVersion version) > +static bool no_cpu_alias; > +void x86_cpu_set_legacy_version(void) > { > - /* Translating CPU_VERSION_AUTO to CPU_VERSION_AUTO doesn't make sense */ > - assert(version != CPU_VERSION_AUTO); > - default_cpu_version = version; > + no_cpu_alias = true; > } > > /* Return the actual version being used for a specific CPU model */ > static X86CPUVersion x86_cpu_model_resolve_version(const X86CPUModel *model) > { > - X86CPUVersion v = model->version; > - if (v == CPU_VERSION_AUTO) { > - v = default_cpu_version; > - } > - return v; > + return model->version; > } > > static const Property max_x86_cpu_properties[] = { > @@ -6251,10 +6237,15 @@ static char *x86_cpu_class_get_alias_of(X86CPUClass *cc) > if (!cc->model || !cc->model->is_alias) { > return NULL; > } > - version = x86_cpu_model_resolve_version(cc->model); > - if (version <= 0) { > + > + if (no_cpu_alias) { > + /* legacy cpu models do not support cpu aliases */ > return NULL; > } > + > + version = x86_cpu_model_resolve_version(cc->model); > + assert(version); > + > return x86_cpu_versioned_model_name(cc->model->cpudef, version); > } > > @@ -6268,11 +6259,7 @@ static void x86_cpu_list_entry(gpointer data, gpointer user_data) > g_autofree char *model_id = x86_cpu_class_get_model_id(cc); > > if (!desc && alias_of) { > - if (cc->model && cc->model->version == CPU_VERSION_AUTO) { > - desc = g_strdup("(alias configured by machine type)"); > - } else { > - desc = g_strdup_printf("(alias of %s)", alias_of); > - } > + desc = g_strdup_printf("(alias of %s)", alias_of); > } > if (!desc && cc->model && cc->model->note) { > desc = g_strdup_printf("%s [%s]", model_id, cc->model->note); > @@ -6375,13 +6362,8 @@ static void x86_cpu_definition_entry(gpointer data, gpointer user_data) > } else { > info->deprecated = false; > } > - /* > - * Old machine types won't report aliases, so that alias translation > - * doesn't break compatibility with previous QEMU versions. > - */ > - if (default_cpu_version != CPU_VERSION_LEGACY) { > - info->alias_of = x86_cpu_class_get_alias_of(cc); > - } > + > + info->alias_of = x86_cpu_class_get_alias_of(cc); > > QAPI_LIST_PREPEND(*cpu_list, info); > } > @@ -6553,10 +6535,6 @@ static void x86_cpu_apply_version_props(X86CPU *cpu, X86CPUModel *model) > const X86CPUVersionDefinition *vdef; > X86CPUVersion version = x86_cpu_model_resolve_version(model); > > - if (version == CPU_VERSION_LEGACY) { > - return; > - } > - > for (vdef = x86_cpu_def_get_versions(model->cpudef); vdef->version; vdef++) { > PropValue *p; > > @@ -6583,10 +6561,6 @@ static const CPUCaches *x86_cpu_get_versioned_cache_info(X86CPU *cpu, > X86CPUVersion version = x86_cpu_model_resolve_version(model); > const CPUCaches *cache_info = model->cpudef->cache_info; > > - if (version == CPU_VERSION_LEGACY) { > - return cache_info; > - } > - > for (vdef = x86_cpu_def_get_versions(model->cpudef); vdef->version; vdef++) { > if (vdef->cache_info) { > cache_info = vdef->cache_info; > @@ -6718,7 +6692,7 @@ static void x86_register_cpudef_types(const X86CPUDefinition *def) > /* Unversioned model: */ > m = g_new0(X86CPUModel, 1); > m->cpudef = def; > - m->version = CPU_VERSION_AUTO; > + m->version = 1; > m->is_alias = true; > x86_register_cpu_model_type(def->name, m); > > diff --git a/target/i386/cpu.h b/target/i386/cpu.h > index 113cf10aea..ee1edaa987 100644 > --- a/target/i386/cpu.h > +++ b/target/i386/cpu.h > @@ -2739,23 +2739,9 @@ void cpu_report_tpr_access(CPUX86State *env, TPRAccess access); > void apic_handle_tpr_access_report(DeviceState *d, target_ulong ip, > TPRAccess access); > > -/* Special values for X86CPUVersion: */ > -/* > - * Resolve to version defined by current machine type. > - * See x86_cpu_set_default_version() > - */ > -#define CPU_VERSION_AUTO -2 > - > -/* Don't resolve to any versioned CPU models, like old QEMU versions */ > -#define CPU_VERSION_LEGACY 0 > - > typedef int X86CPUVersion; > > -/* > - * Set default CPU model version for CPU models having > - * version == CPU_VERSION_AUTO. > - */ > -void x86_cpu_set_default_version(X86CPUVersion version); > +void x86_cpu_set_legacy_version(void); > > #ifndef CONFIG_USER_ONLY > > -- > 2.45.2