| Message ID | 20241208064810.893451-1-anisinha@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | hw/i386/cpu: remove default_cpu_version and simplify | expand |
+Daniel, On Sun, Dec 08, 2024 at 12:18:10PM +0530, Ani Sinha wrote: > Date: Sun, 8 Dec 2024 12:18:10 +0530 > From: Ani Sinha <anisinha@redhat.com> > Subject: [PATCH] hw/i386/cpu: remove default_cpu_version and simplify > X-Mailer: git-send-email 2.45.2 > > 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]. > > Unfortunately, all pc machines still use the default cpu version of 1 for > unversioned cpu models. Only microvms use CPU_VERSION_LATEST. Hi Ani, So could we use CPU_VERSION_LATEST for other machines now? Mapping unversioned cpu models to the latest version sounds like more user friendly. Regards, Zhao > This change cleans up the complicated logic around default_cpu_version > including getting rid of default_cpu_version property itself. A couple of new > flags are introduced, one for the legacy model for machines 4.0.1 and older > and other for microvms. 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. Microvms are the only machines that > continue to use the latest cpu version. If this changes later, we can > remove all logic around x86_cpu_model_last_version(). Default cpu version > for unversioned cpu models is hardcoded to the value 1 and applies > unconditionally for all pc machine types of version 4.1 and above. > > 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") > > CC: imammedo@redhat.com > Signed-off-by: Ani Sinha <anisinha@redhat.com>
> On 9 Dec 2024, at 8:40 PM, Zhao Liu <zhao1.liu@intel.com> wrote: > > +Daniel, > > On Sun, Dec 08, 2024 at 12:18:10PM +0530, Ani Sinha wrote: >> Date: Sun, 8 Dec 2024 12:18:10 +0530 >> From: Ani Sinha <anisinha@redhat.com> >> Subject: [PATCH] hw/i386/cpu: remove default_cpu_version and simplify >> X-Mailer: git-send-email 2.45.2 >> >> 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]. >> >> Unfortunately, all pc machines still use the default cpu version of 1 for >> unversioned cpu models. Only microvms use CPU_VERSION_LATEST. > > Hi Ani, > > So could we use CPU_VERSION_LATEST for other machines now? > > Mapping unversioned cpu models to the latest version sounds like more > user friendly. Note that even though that was the intention when default_cpu_version was introduced, it was never done that way. We have been using cpu version 1 for a long time. > > Regards, > Zhao > >> This change cleans up the complicated logic around default_cpu_version >> including getting rid of default_cpu_version property itself. A couple of new >> flags are introduced, one for the legacy model for machines 4.0.1 and older >> and other for microvms. 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. Microvms are the only machines that >> continue to use the latest cpu version. If this changes later, we can >> remove all logic around x86_cpu_model_last_version(). Default cpu version >> for unversioned cpu models is hardcoded to the value 1 and applies >> unconditionally for all pc machine types of version 4.1 and above. >> >> 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") >> >> CC: imammedo@redhat.com >> Signed-off-by: Ani Sinha <anisinha@redhat.com>
> On 9 Dec 2024, at 9:08 PM, Ani Sinha <anisinha@redhat.com> wrote: > > > >> On 9 Dec 2024, at 8:40 PM, Zhao Liu <zhao1.liu@intel.com> wrote: >> >> +Daniel, >> >> On Sun, Dec 08, 2024 at 12:18:10PM +0530, Ani Sinha wrote: >>> Date: Sun, 8 Dec 2024 12:18:10 +0530 >>> From: Ani Sinha <anisinha@redhat.com> >>> Subject: [PATCH] hw/i386/cpu: remove default_cpu_version and simplify >>> X-Mailer: git-send-email 2.45.2 >>> >>> 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]. >>> >>> Unfortunately, all pc machines still use the default cpu version of 1 for >>> unversioned cpu models. Only microvms use CPU_VERSION_LATEST. >> >> Hi Ani, >> >> So could we use CPU_VERSION_LATEST for other machines now? >> >> Mapping unversioned cpu models to the latest version sounds like more >> user friendly. > > Note that even though that was the intention when default_cpu_version was introduced, it was never done that way. We have been using cpu version 1 for a long time. Had a conversation with Igor offline. CPU_VERSION_LATEST does not work since it’s a moving target. Therefore for a specific machine, what version of cpu model will be chosen will depend on what is latest and this will change with time. It can break guests that stick to a single cpu model. One way to fix this would be to keep a fixed mapping between cpu model and machine versions. However, it will be a nightmare to maintain such mappings. > >> >> Regards, >> Zhao >> >>> This change cleans up the complicated logic around default_cpu_version >>> including getting rid of default_cpu_version property itself. A couple of new >>> flags are introduced, one for the legacy model for machines 4.0.1 and older >>> and other for microvms. 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. Microvms are the only machines that >>> continue to use the latest cpu version. If this changes later, we can >>> remove all logic around x86_cpu_model_last_version(). Default cpu version >>> for unversioned cpu models is hardcoded to the value 1 and applies >>> unconditionally for all pc machine types of version 4.1 and above. >>> >>> 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") >>> >>> CC: imammedo@redhat.com >>> Signed-off-by: Ani Sinha <anisinha@redhat.com>
> Had a conversation with Igor offline. CPU_VERSION_LATEST does not work since it’s a moving target. Therefore for a specific machine, what version of cpu model will be chosen will depend on what is latest and this will change with time. It can break guests that stick to a single cpu model. > > One way to fix this would be to keep a fixed mapping between cpu model and machine versions. However, it will be a nightmare to maintain such mappings. Thanks Ani! The commit ad18392 also mentioned the plan to move to CPU_VERSION_LATEST. Because previsou commits have repeatedly mentioned the plan to move to CPU_VERSION_LATEST (not only the commit dcafd1ef0af227 you referred, but also the commit ad18392), I think it's necessary to include the termination of this plan (i.e., your explanation of why you are no longer attempting to move to CPU_VERSION_LATEST) in the commit message. This way, the history regarding default_cpu_version will be easier to search, and it effectively puts an end to the previous plan. Thanks, Zhao
On Thu, Dec 12, 2024 at 7:25 PM Zhao Liu <zhao1.liu@intel.com> wrote: > > > Had a conversation with Igor offline. CPU_VERSION_LATEST does not work since it’s a moving target. Therefore for a specific machine, what version of cpu model will be chosen will depend on what is latest and this will change with time. It can break guests that stick to a single cpu model. > > > > One way to fix this would be to keep a fixed mapping between cpu model and machine versions. However, it will be a nightmare to maintain such mappings. > > Thanks Ani! > > The commit ad18392 also mentioned the plan to move to CPU_VERSION_LATEST. > > Because previsou commits have repeatedly mentioned the plan to move to > CPU_VERSION_LATEST (not only the commit dcafd1ef0af227 you referred, but > also the commit ad18392), I think it's necessary to include the > termination of this plan (i.e., your explanation of why you are no longer > attempting to move to CPU_VERSION_LATEST) in the commit message. > > This way, the history regarding default_cpu_version will be easier to > search, and it effectively puts an end to the previous plan. OK I added a comment in v2. > > Thanks, > Zhao >
diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c index 86637afa0f..2cbe08caea 100644 --- a/hw/i386/microvm.c +++ b/hw/i386/microvm.c @@ -458,7 +458,7 @@ static void microvm_machine_state_init(MachineState *machine) microvm_memory_init(mms); - x86_cpus_init(x86ms, CPU_VERSION_LATEST); + x86_cpus_init_with_latest_cpu_version(x86ms); microvm_devices_init(mms); } diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c index 2bf6865d40..8e0ab0387f 100644 --- a/hw/i386/pc_piix.c +++ b/hw/i386/pc_piix.c @@ -181,7 +181,8 @@ static void pc_init1(MachineState *machine, const char *pci_type) } pc_machine_init_sgx_epc(pcms); - x86_cpus_init(x86ms, pcmc->default_cpu_version); + + pc_init_cpus(machine); if (kvm_enabled()) { kvmclock_create(pcmc->kvmclock_create_always); @@ -454,7 +455,6 @@ 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)"; @@ -661,7 +661,7 @@ 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 8319b6d45e..9a4f14b336 100644 --- a/hw/i386/pc_q35.c +++ b/hw/i386/pc_q35.c @@ -187,7 +187,8 @@ static void pc_q35_init(MachineState *machine) } pc_machine_init_sgx_epc(pcms); - x86_cpus_init(x86ms, pcmc->default_cpu_version); + + pc_init_cpus(machine); if (kvm_enabled()) { kvmclock_create(pcmc->kvmclock_create_always); @@ -336,7 +337,6 @@ 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)"; @@ -537,7 +537,7 @@ 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 dc031af662..37dfdb7300 100644 --- a/hw/i386/x86-common.c +++ b/hw/i386/x86-common.c @@ -66,15 +66,24 @@ out: object_unref(cpu); } -void x86_cpus_init(X86MachineState *x86ms, int default_cpu_version) +void x86_legacy_cpus_init(X86MachineState *x86ms) +{ + machine_uses_legacy_cpu(); + x86_cpus_init(x86ms); +} + +void x86_cpus_init_with_latest_cpu_version(X86MachineState *x86ms) +{ + x86_cpu_uses_lastest_version(); + x86_cpus_init(x86ms); +} +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 14ee06287d..b514b957d9 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; @@ -125,11 +122,29 @@ 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" OBJECT_DECLARE_TYPE(PCMachineState, PCMachineClass, PC_MACHINE) +static inline void pc_init_cpus(MachineState *ms) +{ + X86MachineState *x86ms = X86_MACHINE(ms); + PCMachineState *pcms = PC_MACHINE(ms); + PCMachineClass *pcmc = PC_MACHINE_GET_CLASS(pcms); + + if (pcmc->no_versioned_cpu_model) { + /* use legacy cpu as it does not support versions */ + x86_legacy_cpus_init(x86ms); + } else { + /* use non-legacy cpus */ + x86_cpus_init(x86ms); + } +} + /* ioapic.c */ GSIState *pc_gsi_create(qemu_irq **irqs, bool pci_enabled); diff --git a/include/hw/i386/x86.h b/include/hw/i386/x86.h index d43cb3908e..a90464f74b 100644 --- a/include/hw/i386/x86.h +++ b/include/hw/i386/x86.h @@ -114,7 +114,10 @@ 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_legacy_cpus_init(X86MachineState *x86ms); +void x86_cpus_init_with_latest_cpu_version(X86MachineState *x86ms); + 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 3725dbbc4b..14f5aa359b 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -191,6 +191,9 @@ struct CPUID2CacheDescriptorInfo cpuid2_cache_descriptors[] = { */ #define CACHE_DESCRIPTOR_UNAVAILABLE 0xFF +/* default cpu version to use */ +#define DEFAULT_CPU_VERSION 1 + /* * Return a CPUID 2 cache descriptor for a given cache. * If no known descriptor is found, return CACHE_DESCRIPTOR_UNAVAILABLE @@ -5343,20 +5346,16 @@ 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; +static bool use_legacy_cpu; +void machine_uses_legacy_cpu(void) +{ + use_legacy_cpu = true; +} -void x86_cpu_set_default_version(X86CPUVersion version) +static bool use_last_cpu_version; +void x86_cpu_uses_lastest_version(void) { - /* Translating CPU_VERSION_AUTO to CPU_VERSION_AUTO doesn't make sense */ - assert(version != CPU_VERSION_AUTO); - default_cpu_version = version; + use_last_cpu_version = true; } static X86CPUVersion x86_cpu_model_last_version(const X86CPUModel *model) @@ -5374,14 +5373,11 @@ static X86CPUVersion x86_cpu_model_last_version(const X86CPUModel *model) /* 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; - } - if (v == CPU_VERSION_LATEST) { + if (use_last_cpu_version) { return x86_cpu_model_last_version(model); } - return v; + + return model->version; } static Property max_x86_cpu_properties[] = { @@ -5986,6 +5982,12 @@ static char *x86_cpu_class_get_alias_of(X86CPUClass *cc) if (!cc->model || !cc->model->is_alias) { return NULL; } + + if (use_legacy_cpu) { + /* legacy cpu models do not support cpu aliases */ + return NULL; + } + version = x86_cpu_model_resolve_version(cc->model); if (version <= 0) { return NULL; @@ -6003,11 +6005,7 @@ 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); - } } if (!desc && cc->model && cc->model->note) { desc = g_strdup_printf("%s [%s]", model_id, cc->model->note); @@ -6114,7 +6112,7 @@ static void x86_cpu_definition_entry(gpointer data, gpointer user_data) * 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) { + if (!use_legacy_cpu) { info->alias_of = x86_cpu_class_get_alias_of(cc); } @@ -6288,7 +6286,7 @@ 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) { + if (use_legacy_cpu) { return; } @@ -6318,7 +6316,7 @@ 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) { + if (use_legacy_cpu) { return cache_info; } @@ -6453,7 +6451,7 @@ 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 = DEFAULT_CPU_VERSION; 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 4c239a6970..5ad80c8a97 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -2658,28 +2658,15 @@ 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 latest CPU version */ -#define CPU_VERSION_LATEST -1 - -/* - * 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. + * Set CPU model version to the lastest version. + * Currently, this is only used by microvm. */ -void x86_cpu_set_default_version(X86CPUVersion version); +void x86_cpu_uses_lastest_version(void); +void machine_uses_legacy_cpu(void); #ifndef CONFIG_USER_ONLY void do_cpu_sipi(X86CPU *cpu);
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]. Unfortunately, all pc machines still use the default cpu version of 1 for unversioned cpu models. Only microvms use CPU_VERSION_LATEST. This change cleans up the complicated logic around default_cpu_version including getting rid of default_cpu_version property itself. A couple of new flags are introduced, one for the legacy model for machines 4.0.1 and older and other for microvms. 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. Microvms are the only machines that continue to use the latest cpu version. If this changes later, we can remove all logic around x86_cpu_model_last_version(). Default cpu version for unversioned cpu models is hardcoded to the value 1 and applies unconditionally for all pc machine types of version 4.1 and above. 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") CC: imammedo@redhat.com Signed-off-by: Ani Sinha <anisinha@redhat.com> --- hw/i386/microvm.c | 2 +- hw/i386/pc_piix.c | 6 +++--- hw/i386/pc_q35.c | 6 +++--- hw/i386/x86-common.c | 15 ++++++++++--- include/hw/i386/pc.h | 21 +++++++++++++++--- include/hw/i386/x86.h | 5 ++++- target/i386/cpu.c | 50 +++++++++++++++++++++---------------------- target/i386/cpu.h | 21 ++++-------------- 8 files changed, 69 insertions(+), 57 deletions(-)