Re: [Xen-devel] [PATCH 3/8] x86/vm-event/monitor: relocate code-motion more appropriately

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.06.16 at 20:43, <czuzu@xxxxxxxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -475,8 +475,6 @@ void hvm_do_resume(struct vcpu *v)
>  
>      if ( unlikely(v->arch.vm_event) )
>      {
> -        struct monitor_write_data *w = &v->arch.vm_event->write_data;
> -
>          if ( v->arch.vm_event->emulate_flags )
>          {
>              enum emul_kind kind = EMUL_KIND_NORMAL;
> @@ -493,32 +491,10 @@ void hvm_do_resume(struct vcpu *v)
>  
>              v->arch.vm_event->emulate_flags = 0;
>          }
> -
> -        if ( w->do_write.msr )
> -        {
> -            hvm_msr_write_intercept(w->msr, w->value, 0);
> -            w->do_write.msr = 0;
> -        }
> -
> -        if ( w->do_write.cr0 )
> -        {
> -            hvm_set_cr0(w->cr0, 0);
> -            w->do_write.cr0 = 0;
> -        }
> -
> -        if ( w->do_write.cr4 )
> -        {
> -            hvm_set_cr4(w->cr4, 0);
> -            w->do_write.cr4 = 0;
> -        }
> -
> -        if ( w->do_write.cr3 )
> -        {
> -            hvm_set_cr3(w->cr3, 0);
> -            w->do_write.cr3 = 0;
> -        }
>      }
>  
> +    arch_monitor_write_data(v);

Why does this get moved outside the if(), with the same condition
getting added inside the function (inverted for bailing early)?

> @@ -119,6 +156,55 @@ bool_t monitored_msr(const struct domain *d, u32 msr)
>      return test_bit(msr, bitmap);
>  }
>  
> +static void write_ctrlreg_adjust_traps(struct domain *d)
> +{
> +    struct vcpu *v;
> +    struct arch_vmx_struct *avmx;
> +    unsigned int cr3_bitmask;
> +    bool_t cr3_vmevent, cr3_ldexit;
> +
> +    /* Adjust CR3 load-exiting. */
> +
> +    /* vmx only */
> +    ASSERT(cpu_has_vmx);
> +
> +    /* non-hap domains trap CR3 writes unconditionally */
> +    if ( !paging_mode_hap(d) )
> +    {
> +        for_each_vcpu ( d, v )
> +            ASSERT(v->arch.hvm_vmx.exec_control & 
> CPU_BASED_CR3_LOAD_EXITING);
> +        return;
> +    }
> +
> +    cr3_bitmask = monitor_ctrlreg_bitmask(VM_EVENT_X86_CR3);
> +    cr3_vmevent = !!(d->arch.monitor.write_ctrlreg_enabled & cr3_bitmask);
> +
> +    for_each_vcpu ( d, v )
> +    {
> +        avmx = &v->arch.hvm_vmx;
> +        cr3_ldexit = !!(avmx->exec_control & CPU_BASED_CR3_LOAD_EXITING);
> +
> +        if ( cr3_vmevent == cr3_ldexit )
> +            continue;
> +
> +        /*
> +         * If CR0.PE=0, CR3 load exiting must remain enabled.
> +         * See vmx_update_guest_cr code motion for cr = 0.
> +         */
> +        if ( cr3_ldexit && !hvm_paging_enabled(v) && 
> !vmx_unrestricted_guest(v) 
> )
> +            continue;
> +
> +        if ( cr3_vmevent )
> +            avmx->exec_control |= CPU_BASED_CR3_LOAD_EXITING;
> +        else
> +            avmx->exec_control &= ~CPU_BASED_CR3_LOAD_EXITING;
> +
> +        vmx_vmcs_enter(v);
> +        vmx_update_cpu_exec_control(v);
> +        vmx_vmcs_exit(v);
> +    }
> +}

While Razvan gave his ack already, I wonder whether it's really a
good idea to put deeply VMX-specific code outside of a VMX-specific
file.

Jan


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