Re: [PATCH v7 09/10] xen/vmtrace: support for VM forks

[Jan Beulich <jbeulich@xxxxxxxx>]

On 21.01.2021 22:27, Andrew Cooper wrote:
> From: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
> 
> Implement vmtrace_reset_pt function. Properly set IPT
> state for VM forks.
> 
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
albeit it strikes me as somewhat odd that ...

> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -2408,6 +2408,16 @@ static int vmtrace_output_position(struct vcpu *v, 
> uint64_t *pos)
>      return v->arch.hvm.vmx.ipt_active;
>  }
>  
> +static int vmtrace_reset(struct vcpu *v)
> +{
> +    if ( !v->arch.hvm.vmx.ipt_active )
> +        return -EINVAL;
> +
> +    v->arch.msrs->rtit.output_offset = 0;
> +    v->arch.msrs->rtit.status = 0;
> +    return 0;
> +}

... the function/hook return non-void, yet ...

> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -1632,6 +1632,8 @@ static int copy_vcpu_settings(struct domain *cd, const 
> struct domain *d)
>              copy_domain_page(new_vcpu_info_mfn, vcpu_info_mfn);
>          }
>  
> +        hvm_vmtrace_reset(cd_vcpu);

... the only caller doesn't care.

Jan