Re: [Xen-devel] [PATCH v7 11/15] x86/altp2m: define and implement alternate p2m HVMOP types.

["Sahita, Ravi" <ravi.sahita@xxxxxxxxx>]

>From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
>Sent: Thursday, July 23, 2015 3:22 AM
>
>>>> On 23.07.15 at 01:01, <edmund.h.white@xxxxxxxxx> wrote:
>> Signed-off-by: Ed White <edmund.h.white@xxxxxxxxx>
>>
>> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>
>And I have to withdraw this ack pending clarification of (and perhaps
>adjustment to) the #VE info address interface.
>

Could we have the ack back :-) I clarified the #VE info address interface in 
the other email - repeating here:

" If the "EPT-violation #VE" VM-execution control is 1, the 
virtualization-exception information address must
satisfy the following checks:
- Bits 11:0 of the address must be 0.
- The address must not set any bits beyond the processor's physical-address 
width."


>> --- a/xen/arch/x86/hvm/hvm.c
>> +++ b/xen/arch/x86/hvm/hvm.c
>> @@ -6138,6 +6138,140 @@ static int hvmop_get_param(
>>      return rc;
>>  }
>>
>> +static int do_altp2m_op(
>> +    XEN_GUEST_HANDLE_PARAM(void) arg) {
>> +    struct xen_hvm_altp2m_op a;
>> +    struct domain *d = NULL;
>> +    int rc = 0;
>> +
>> +    if ( !hvm_altp2m_supported() )
>> +        return -EOPNOTSUPP;
>> +
>> +    if ( copy_from_guest(&a, arg, 1) )
>> +        return -EFAULT;
>> +
>> +    if ( a.pad1 || a.pad2 ||
>> +         (a.version != HVMOP_ALTP2M_INTERFACE_VERSION) ||
>> +         (a.cmd < HVMOP_altp2m_get_domain_state) ||
>> +         (a.cmd > HVMOP_altp2m_change_gfn) )
>
>I'm afraid such a change invalidates any earlier ack, even if ti is correct. 
>Instead
>of this, why don't you start numbering of the sub-ops at zero? Or if you really
>have a reason to start at 1, why not simply check a.cmd against zero (without
>using any particular sub-op value)? And then it escapes me why this can't be
>handled in a default case in the switch statement below anyway.

Hmm - is that a requirement per se? we are consistently checking per the sub-op 
definition we have.
Would like this to be considered as is. 

As I said in the cover letter we have constraints on how much more we can do 
this week now - 
so requesting the maintainers to accept v7 with the review comments you have on 
those recorded as pending to be addressed by us.

Thanks much!
Ravi



>
>Jan


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