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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.04.18 at 13:37, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 13/04/18 09:39, Jan Beulich wrote:
>>>>> 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)?
> 
> The upper 32 bits are MBZ and will raise #GP if set.  The lower reserved
> bits are write-ignored.

Oh, indeed, I didn't recall that.

Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel