Re: [Qemu-devel] [patch 2/2] target-i386: block migration and savevm if invariant tsc is exposed

[Eduardo Habkost]

On Wed, Apr 23, 2014 at 03:20:04PM -0300, Marcelo Tosatti wrote:
> Invariant TSC documentation mentions that "invariant TSC will run at a
> constant rate in all ACPI P-, C-. and T-states".
> 
> This is not the case if migration to a host with different TSC frequency 
> is allowed, or if savevm is performed. So block migration/savevm.
> 
> Also do not expose invariant tsc flag by default.

You probably want to remove the above line?

> 
> Signed-off-by: Marcelo Tosatti <address@hidden>
> 
> Index: qemu-invariant-tsc/target-i386/kvm.c
> ===================================================================
> --- qemu-invariant-tsc.orig/target-i386/kvm.c
> +++ qemu-invariant-tsc/target-i386/kvm.c
> @@ -33,6 +33,8 @@
>  #include "exec/ioport.h"
>  #include <asm/hyperv.h>
>  #include "hw/pci/pci.h"
> +#include "migration/migration.h"
> +#include "qapi/qmp/qerror.h"
>  
>  //#define DEBUG_KVM
>  
> @@ -447,6 +449,8 @@ static bool hyperv_enabled(X86CPU *cpu)
>              cpu->hyperv_relaxed_timing);
>  }
>  
> +Error *invtsc_mig_blocker;
> +
>  #define KVM_MAX_CPUID_ENTRIES  100
>  
>  int kvm_arch_init_vcpu(CPUState *cs)
> @@ -702,6 +706,15 @@ int kvm_arch_init_vcpu(CPUState *cs)
>                                    !!(c->ecx & CPUID_EXT_SMX);
>      }
>  
> +    c = cpuid_find_entry(&cpuid_data.cpuid, 0x80000007, 0);
> +    if (c && (c->edx & 1<<8) && invtsc_mig_blocker == NULL) {
> +        /* for migration */
> +        error_set(&invtsc_mig_blocker, QERR_MIGRATION_NOT_SUPPORTED, "cpu");

What about using QERR_DEVICE_FEATURE_BLOCKS_MIGRATION, "invtsc", "cpu"?

> +        migrate_add_blocker(invtsc_mig_blocker);
> +        /* for savevm */
> +        vmstate_x86_cpu.unmigratable = 1;
> +    }
> +
>      cpuid_data.cpuid.padding = 0;
>      r = kvm_vcpu_ioctl(cs, KVM_SET_CPUID2, &cpuid_data);
>      if (r) {
> Index: qemu-invariant-tsc/target-i386/cpu-qom.h
> ===================================================================
> --- qemu-invariant-tsc.orig/target-i386/cpu-qom.h
> +++ qemu-invariant-tsc/target-i386/cpu-qom.h
> @@ -116,7 +116,7 @@ static inline X86CPU *x86_env_get_cpu(CP
>  #define ENV_OFFSET offsetof(X86CPU, env)
>  
>  #ifndef CONFIG_USER_ONLY
> -extern const struct VMStateDescription vmstate_x86_cpu;
> +extern struct VMStateDescription vmstate_x86_cpu;
>  #endif
>  
>  /**
> Index: qemu-invariant-tsc/target-i386/machine.c
> ===================================================================
> --- qemu-invariant-tsc.orig/target-i386/machine.c
> +++ qemu-invariant-tsc/target-i386/machine.c
> @@ -613,7 +613,7 @@ static const VMStateDescription vmstate_
>      }
>  };
>  
> -const VMStateDescription vmstate_x86_cpu = {
> +VMStateDescription vmstate_x86_cpu = {
>      .name = "cpu",
>      .version_id = 12,
>      .minimum_version_id = 3,
> 
> 

-- 
Eduardo