Re: [Qemu-devel] [PATCH] Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs

[Jan Kiszka]

On 2012-09-19 19:49, Auld, Will wrote:
> From 9d5201975d2c9da4da8a945fcd9531c9fb2073c0 Mon Sep 17 00:00:00 2001
> From: Will Auld <address@hidden>
> Date: Wed, 12 Sep 2012 18:31:41 -0700
> Subject: [PATCH] Enabling IA32_TSC_ADJUST for Qemu KVM guest VMs
> 
> CPUID.7.0.EBX[1]=1 indicates IA32_TSC_ADJUST MSR 0x3b is supported
> 
> Basic design is to emulate the MSR by allowing reads and writes to the
> hypervisor vcpu specific locations to store the value of the emulated MSRs.
> In this way the IA32_TSC_ADJUST value will be included in all reads to
> the TSC MSR whether through rdmsr or rdtsc.
> 
> As this is a new MSR that the guest may access and modify its value needs
> to be migrated along with the other MRSs. The changes here are specifically
> for recognizing when IA32_TSC_ADJUST is enabled in CPUID and code added
> for migrating its value.
> ---
>  target-i386/cpu.h     |    4 +++-
>  target-i386/kvm.c     |   15 +++++++++++++++
>  target-i386/machine.c |   21 +++++++++++++++++++++
>  3 files changed, 39 insertions(+), 1 deletions(-)
> 
> diff --git a/target-i386/cpu.h b/target-i386/cpu.h
> index aabf993..7ca99c0 100644
> --- a/target-i386/cpu.h
> +++ b/target-i386/cpu.h
> @@ -284,6 +284,7 @@
>  #define MSR_IA32_APICBASE_BSP           (1<<8)
>  #define MSR_IA32_APICBASE_ENABLE        (1<<11)
>  #define MSR_IA32_APICBASE_BASE          (0xfffff<<12)
> +#define MSR_TSC_ADJUST                       0x0000003b
>  #define MSR_IA32_TSCDEADLINE            0x6e0
>  
>  #define MSR_MTRRcap                  0xfe
> @@ -701,6 +702,7 @@ typedef struct CPUX86State {
>      uint64_t async_pf_en_msr;
>  
>      uint64_t tsc;
> +    uint64_t tsc_adjust;
>      uint64_t tsc_deadline;
>  
>      uint64_t mcg_status;
> @@ -979,7 +981,7 @@ static inline CPUX86State *cpu_init(const char *cpu_model)
>  #define cpu_list_id x86_cpu_list
>  #define cpudef_setup x86_cpudef_setup
>  
> -#define CPU_SAVE_VERSION 12
> +#define CPU_SAVE_VERSION 13

That bump is not needed as you append the new field via a subsection.

Jan

>  
>  /* MMU modes definitions */
>  #define MMU_MODE0_SUFFIX _kernel
> diff --git a/target-i386/kvm.c b/target-i386/kvm.c
> index 696b14a..e974c42 100644
> --- a/target-i386/kvm.c
> +++ b/target-i386/kvm.c
> @@ -61,6 +61,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
>  
>  static bool has_msr_star;
>  static bool has_msr_hsave_pa;
> +static bool has_msr_tsc_adjust;
>  static bool has_msr_tsc_deadline;
>  static bool has_msr_async_pf_en;
>  static bool has_msr_misc_enable;
> @@ -641,6 +642,10 @@ static int kvm_get_supported_msrs(KVMState *s)
>                      has_msr_hsave_pa = true;
>                      continue;
>                  }
> +                if (kvm_msr_list->indices[i] == MSR_TSC_ADJUST) {
> +                    has_msr_tsc_adjust = true;
> +                    continue;
> +                }
>                  if (kvm_msr_list->indices[i] == MSR_IA32_TSCDEADLINE) {
>                      has_msr_tsc_deadline = true;
>                      continue;
> @@ -978,6 +983,10 @@ static int kvm_put_msrs(CPUX86State *env, int level)
>      if (has_msr_hsave_pa) {
>          kvm_msr_entry_set(&msrs[n++], MSR_VM_HSAVE_PA, env->vm_hsave);
>      }
> +    if (has_msr_tsc_adjust) {
> +        kvm_msr_entry_set(&msrs[n++],
> +                     MSR_TSC_ADJUST, env->tsc_adjust);
> +    }
>      if (has_msr_tsc_deadline) {
>          kvm_msr_entry_set(&msrs[n++], MSR_IA32_TSCDEADLINE, 
> env->tsc_deadline);
>      }
> @@ -1234,6 +1243,9 @@ static int kvm_get_msrs(CPUX86State *env)
>      if (has_msr_hsave_pa) {
>          msrs[n++].index = MSR_VM_HSAVE_PA;
>      }
> +    if (has_msr_tsc_adjust) {
> +        msrs[n++].index = MSR_TSC_ADJUST;
> +    }
>      if (has_msr_tsc_deadline) {
>          msrs[n++].index = MSR_IA32_TSCDEADLINE;
>      }
> @@ -1308,6 +1320,9 @@ static int kvm_get_msrs(CPUX86State *env)
>          case MSR_IA32_TSC:
>              env->tsc = msrs[i].data;
>              break;
> +        case MSR_TSC_ADJUST:
> +            env->tsc_adjust = msrs[i].data;
> +            break;
>          case MSR_IA32_TSCDEADLINE:
>              env->tsc_deadline = msrs[i].data;
>              break;
> diff --git a/target-i386/machine.c b/target-i386/machine.c
> index a8be058..95bda9b 100644
> --- a/target-i386/machine.c
> +++ b/target-i386/machine.c
> @@ -310,6 +310,24 @@ static const VMStateDescription vmstate_fpop_ip_dp = {
>      }
>  };
>  
> +static bool tsc_adjust_needed(void *opaque)
> +{
> +    CPUX86State *cpu = opaque;
> +
> +    return cpu->tsc_adjust != 0;
> +}
> +
> +static const VMStateDescription vmstate_msr_tsc_adjust = {
> +    .name = "cpu/msr_tsc_adjust",
> +    .version_id = 1,
> +    .minimum_version_id = 1,
> +    .minimum_version_id_old = 1,
> +    .fields      = (VMStateField []) {
> +        VMSTATE_UINT64(tsc_adjust, CPUX86State),
> +        VMSTATE_END_OF_LIST()
> +    }
> +};
> +
>  static bool tscdeadline_needed(void *opaque)
>  {
>      CPUX86State *env = opaque;
> @@ -457,6 +475,9 @@ static const VMStateDescription vmstate_cpu = {
>              .vmsd = &vmstate_fpop_ip_dp,
>              .needed = fpop_ip_dp_needed,
>          }, {
> +            .vmsd = &vmstate_msr_tsc_adjust,
> +            .needed = tsc_adjust_needed,
> +        }, {
>              .vmsd = &vmstate_msr_tscdeadline,
>              .needed = tscdeadline_needed,
>          }, {
> 
-- 
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Corporate Competence Center Embedded Linux