Re: [PATCH v11 for-xen-4.5 13/20] x86/VPMU: Save VPMU state for PV guests during context switch

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Sep 22, 2014 at 07:57:54PM -0400, Boris Ostrovsky wrote:
> Save VPMU state during context switch for both HVM and PV(H) guests.
> 
> A subsequent patch will make it possible for vpmu_switch_to() to call

Could you say what is the name of the 'subsequent patch' in the commit
description please?

> vmx_vmcs_try_enter()->vcpu_pause() which needs is_running to be correctly
> set/cleared. To prepare for that, call context_saved() before vpmu_switch_to()
> is executed.

And what ramifications does that have to the guests if one only applied
patches up to this point?

> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> ---
>  xen/arch/x86/domain.c | 20 +++++++++-----------
>  1 file changed, 9 insertions(+), 11 deletions(-)
> 
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index 5e492d8..d7fb99d 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -1495,16 +1495,13 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
>      }
>  
>      if ( prev != next )
> -        _update_runstate_area(prev);
> -
> -    if ( is_hvm_vcpu(prev) )
>      {
> -        if (prev != next)
> -            vpmu_switch_from(prev, next);
> +        _update_runstate_area(prev);
> +        vpmu_switch_from(prev, next);
> +    }
>  
> -        if ( !list_empty(&prev->arch.hvm_vcpu.tm_list) )
> +    if ( is_hvm_vcpu(prev) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
>              pt_save_timer(prev);
> -    }
>  
>      local_irq_disable();
>  
> @@ -1543,15 +1540,16 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
>                             !is_hardware_domain(next->domain));
>      }
>  
> -    if ( is_hvm_vcpu(prev) && (prev != next) )
> -        /* Must be done with interrupts enabled */
> -        vpmu_switch_to(prev, next);
> -
>      context_saved(prev);
>  
>      if ( prev != next )
> +    {
>          _update_runstate_area(next);
>  
> +        /* Must be done with interrupts enabled */
> +        vpmu_switch_to(prev, next);
> +    }
> +
>      /* Ensure that the vcpu has an up-to-date time base. */
>      update_vcpu_system_time(next);
>  
> -- 
> 1.8.1.4
> 
> 
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