Re: [Xen-devel] [PATCH 2/3] x86/pv: Introduce and use x86emul_write_dr()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.04.18 at 18:55, <andrew.cooper3@xxxxxxxxxx> wrote:
> @@ -2029,7 +2035,17 @@ long set_debugreg(struct vcpu *v, unsigned int reg, 
> unsigned long value)
>          if ( v == curr )
>              write_debugreg(3, value);
>          break;
> +
> +    case 4:
> +        if ( v->arch.pv_vcpu.ctrlreg[4] & X86_CR4_DE )
> +            return -ENODEV;
> +
> +        /* Fallthrough */
>      case 6:
> +        /* The upper 32 bits are strictly reserved. */
> +        if ( value != (uint32_t)value )
> +            return -EINVAL;
> +
>          /*
>           * DR6: Bits 4-11,16-31 reserved (set to 1).
>           *      Bit 12 reserved (set to 0).

How are the upper 32 bits different from the other reserved bits (named in the
comment visible here)?

> @@ -2039,7 +2055,17 @@ long set_debugreg(struct vcpu *v, unsigned int reg, 
> unsigned long value)
>          if ( v == curr )
>              write_debugreg(6, value);
>          break;
> +
> +    case 5:
> +        if ( v->arch.pv_vcpu.ctrlreg[4] & X86_CR4_DE )
> +            return -ENODEV;
> +
> +        /* Fallthrough */
>      case 7:
> +        /* The upper 32 bits are strictly reserved. */
> +        if ( value != (uint32_t)value )
> +            return -EINVAL;
> +
>          /*
>           * DR7: Bit 10 reserved (set to 1).
>           *      Bits 11-12,14-15 reserved (set to 0).

Same here then.

Jan



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