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

[Marcelo Tosatti]

On Tue, Apr 22, 2014 at 04:10:44PM -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.
> 
> 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 +706,16 @@ 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)) {
> +        /* for migration */
> +        invtsc_mig_blocker = NULL;
> +        error_set(&invtsc_mig_blocker, QERR_MIGRATION_NOT_SUPPORTED, "cpu");
> +        migrate_add_blocker(invtsc_mig_blocker);
> +        /* for savevm */
> +        vmstate_x86_cpu.unmigratable = 1;
> +    }

Oops, broken with multiple CPUs. Please review the rest.