> On 30 May 2025, at 8:37 PM, Igor Mammedov <imamm...@redhat.com> wrote:
>
> On Sun, 11 May 2025 09:40:08 -0400
> "Michael S. Tsirkin" <m...@redhat.com> wrote:
>
>> 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: imamm...@redhat.com
>>> Signed-off-by: Ani Sinha <anisi...@redhat.com>
>>> Reviewed-by: Zhao Liu <zhao1....@intel.com>
>>
>> Anyone merging this? If so:
>> Reviewed-by: Michael S. Tsirkin <m...@redhat.com>
>
> Presumably cpu stuff goes via Paolo's tree.
>
> This cleanup should go together with
> 1) "[PATCH v2] microvm: do not use the lastest cpu version"
> https://lists.nongnu.org/archive/html/qemu-devel/2025-03/msg00094.html
> that I and Intel folks (arguably the single user of microvm) acked.
>
> Ani,
> would this patch work with without [1]?
No.
>
>
>
>>
>>> ---
>>> 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
