| Message ID | 20250220065326.312596-1-anisinha@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] microvm: do not use the lastest cpu version | expand |
On Thu, Feb 20, 2025 at 12:23:26PM +0530, Ani Sinha wrote: > Date: Thu, 20 Feb 2025 12:23:26 +0530 > From: Ani Sinha <anisinha@redhat.com> > Subject: [PATCH v2] microvm: do not use the lastest cpu version > 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]. > > All pc machines still use the default cpu version of 1 for > unversioned cpu models. CPU_VERSION_LATEST is a moving target and > changes with time. Therefore, if machines use CPU_VERSION_LATEST, it would > mean that over a period of time, for the same versioned machine type, > the cpu version would be different depending on what the latest was at that > time. This would break guests even when they use a constant specific > versioned machine type. > Additionally, microvm machines are not versioned anyway and therefore > there is no requirement to use the latest cpu model by default. > Let microvms use the non-versioned cpu model and remove all references > to CPU_VERSION_LATEST as there are no other users (nor we anticipate > future consumers of CPU_VERSION_LATEST). > > Those users who need spefific cpu versions can use explicit version in > the QEMU command line to select the specific cpu version desired. > > CI pipline does not break with this change. > > 1) See commit dcafd1ef0af227 ("i386: Register versioned CPU models") > > CC: imammedo@redhat.com > CC: zhao1.liu@intel.com > Reviewed-by: Igor Mammedov <imammedo@redhat.com> > Reviewed-by: Sergio Lopez <slp@redhat.com> > Signed-off-by: Ani Sinha <anisinha@redhat.com> > --- > hw/i386/microvm.c | 2 +- > target/i386/cpu.c | 15 --------------- > target/i386/cpu.h | 4 ---- > 3 files changed, 1 insertion(+), 20 deletions(-) > > changelog: > v2: tags added, more explanation in the commit log. Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c index a8d354aabe..b8be1542ff 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(x86ms, 1); microvm_devices_init(mms); } diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 72ab147e85..0a95b33d15 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -5513,18 +5513,6 @@ void x86_cpu_set_default_version(X86CPUVersion version) default_cpu_version = version; } -static X86CPUVersion x86_cpu_model_last_version(const X86CPUModel *model) -{ - int v = 0; - const X86CPUVersionDefinition *vdef = - x86_cpu_def_get_versions(model->cpudef); - while (vdef->version) { - v = vdef->version; - vdef++; - } - return v; -} - /* Return the actual version being used for a specific CPU model */ static X86CPUVersion x86_cpu_model_resolve_version(const X86CPUModel *model) { @@ -5532,9 +5520,6 @@ static X86CPUVersion x86_cpu_model_resolve_version(const X86CPUModel *model) if (v == CPU_VERSION_AUTO) { v = default_cpu_version; } - if (v == CPU_VERSION_LATEST) { - return x86_cpu_model_last_version(model); - } return v; } diff --git a/target/i386/cpu.h b/target/i386/cpu.h index c67b42d34f..71f150a05f 100644 --- a/target/i386/cpu.h +++ b/target/i386/cpu.h @@ -2701,10 +2701,6 @@ 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()
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. CPU_VERSION_LATEST is a moving target and changes with time. Therefore, if machines use CPU_VERSION_LATEST, it would mean that over a period of time, for the same versioned machine type, the cpu version would be different depending on what the latest was at that time. This would break guests even when they use a constant specific versioned machine type. Additionally, microvm machines are not versioned anyway and therefore there is no requirement to use the latest cpu model by default. Let microvms use the non-versioned cpu model and remove all references to CPU_VERSION_LATEST as there are no other users (nor we anticipate future consumers of CPU_VERSION_LATEST). Those users who need spefific cpu versions can use explicit version in the QEMU command line to select the specific cpu version desired. CI pipline does not break with this change. 1) See commit dcafd1ef0af227 ("i386: Register versioned CPU models") CC: imammedo@redhat.com CC: zhao1.liu@intel.com Reviewed-by: Igor Mammedov <imammedo@redhat.com> Reviewed-by: Sergio Lopez <slp@redhat.com> Signed-off-by: Ani Sinha <anisinha@redhat.com> --- hw/i386/microvm.c | 2 +- target/i386/cpu.c | 15 --------------- target/i386/cpu.h | 4 ---- 3 files changed, 1 insertion(+), 20 deletions(-) changelog: v2: tags added, more explanation in the commit log.