Re: [Xen-devel] [PATCH v7 02/19] VPMU: Mark context LOADED before registers are loaded

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/06/14 18:39, Boris Ostrovsky wrote:
> Because a PMU interrupt may be generated as soon as PMU registers are loaded 
> (or,
> more precisely, as soon as HW PMU is "armed") we don't want to delay marking
> context as LOADED until after registers are loaded. Otherwise during interrupt
> handling VPMU_CONTEXT_LOADED may not be set and this could be confusing.
>
> (Technically, only SVM needs this change right now since VMX will "arm" PMU 
> later,
> during VMRUN when global control register is loaded from VMCS. However, both
> AMD and Intel code will require this patch when we introduce PV VPMU).
>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
> Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
> Tested-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>

Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

> ---
>  xen/arch/x86/hvm/svm/vpmu.c       | 2 ++
>  xen/arch/x86/hvm/vmx/vpmu_core2.c | 2 ++
>  xen/arch/x86/hvm/vpmu.c           | 3 +--
>  3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/svm/vpmu.c b/xen/arch/x86/hvm/svm/vpmu.c
> index 66a3815..3ac7d53 100644
> --- a/xen/arch/x86/hvm/svm/vpmu.c
> +++ b/xen/arch/x86/hvm/svm/vpmu.c
> @@ -203,6 +203,8 @@ static void amd_vpmu_load(struct vcpu *v)
>          return;
>      }
>  
> +    vpmu_set(vpmu, VPMU_CONTEXT_LOADED);
> +
>      context_load(v);
>  }
>  
> diff --git a/xen/arch/x86/hvm/vmx/vpmu_core2.c 
> b/xen/arch/x86/hvm/vmx/vpmu_core2.c
> index 3129ebd..ccd14d9 100644
> --- a/xen/arch/x86/hvm/vmx/vpmu_core2.c
> +++ b/xen/arch/x86/hvm/vmx/vpmu_core2.c
> @@ -369,6 +369,8 @@ static void core2_vpmu_load(struct vcpu *v)
>      if ( vpmu_is_set(vpmu, VPMU_CONTEXT_LOADED) )
>          return;
>  
> +    vpmu_set(vpmu, VPMU_CONTEXT_LOADED);
> +
>      __core2_vpmu_load(v);
>  }
>  
> diff --git a/xen/arch/x86/hvm/vpmu.c b/xen/arch/x86/hvm/vpmu.c
> index 21fbaba..63765fa 100644
> --- a/xen/arch/x86/hvm/vpmu.c
> +++ b/xen/arch/x86/hvm/vpmu.c
> @@ -211,10 +211,9 @@ void vpmu_load(struct vcpu *v)
>      if ( vpmu->arch_vpmu_ops && vpmu->arch_vpmu_ops->arch_vpmu_load )
>      {
>          apic_write_around(APIC_LVTPC, vpmu->hw_lapic_lvtpc);
> +        /* Arch code needs to set VPMU_CONTEXT_LOADED */
>          vpmu->arch_vpmu_ops->arch_vpmu_load(v);
>      }
> -
> -    vpmu_set(vpmu, VPMU_CONTEXT_LOADED);
>  }
>  
>  void vpmu_initialise(struct vcpu *v)


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