Re: [Xen-devel] [PATCH 05/11] x86/emul: Unfold %cr4.de handling in x86emul_read_dr()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.06.18 at 15:59, <andrew.cooper3@xxxxxxxxxx> wrote:
> No functional change (as curr->arch.debugreg[5] is zero when DE is clear), but
> this change simplifies the following patch.

A comment to this effect would be helpful ...

> --- a/xen/arch/x86/x86_emulate.c
> +++ b/xen/arch/x86/x86_emulate.c
> @@ -101,23 +101,29 @@ int x86emul_read_dr(unsigned int reg, unsigned long 
> *val,
>      switch ( reg )
>      {
>      case 0 ... 3:
> -    case 6:
>          *val = curr->arch.debugreg[reg];
>          break;
>  
> +    case 4:
> +        if ( curr->arch.pv_vcpu.ctrlreg[4] & X86_CR4_DE )
> +            goto ud_fault;
> +
> +        /* Fallthrough */
> +    case 6:
> +        *val = curr->arch.debugreg[6];
> +        break;
> +
> +    case 5:
> +        if ( curr->arch.pv_vcpu.ctrlreg[4] & X86_CR4_DE )
> +            goto ud_fault;
> +
> +        /* Fallthrough */
>      case 7:
>          *val = (curr->arch.debugreg[7] |
>                  curr->arch.debugreg[5]);

... somewhere above here. With that
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



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