Re: [Xen-devel] [v7][PATCH 03/16] xen/passthrough: extend hypercall to support rdm reservation policy

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 07/13/2015 07:47 AM, Chen, Tiejun wrote:
>> Thanks for this; a few more comments...
>>
> 
> Thanks for your time.
> 
>>> @@ -1577,9 +1578,15 @@ int iommu_do_pci_domctl(
>>>           seg = machine_sbdf >> 16;
>>>           bus = PCI_BUS(machine_sbdf);
>>>           devfn = PCI_DEVFN2(machine_sbdf);
>>> +        flag = domctl->u.assign_device.flag;
>>> +        if ( flag > XEN_DOMCTL_DEV_RDM_RELAXED )
>>
>> This is not a blocker, but a stylistic comment: I would have inverted
>> the bitmask here, as that's conceptually what you're checking.  I
>> won't make this a blocker for going in.
> 
> What about this?
> 
> diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
> index 6e23fc6..17a4206 100644
> --- a/xen/drivers/passthrough/pci.c
> +++ b/xen/drivers/passthrough/pci.c
> @@ -1579,7 +1579,7 @@ int iommu_do_pci_domctl(
>          bus = PCI_BUS(machine_sbdf);
>          devfn = PCI_DEVFN2(machine_sbdf);
>          flag = domctl->u.assign_device.flag;
> -        if ( flag > XEN_DOMCTL_DEV_RDM_RELAXED )
> +        if ( flag & ~XEN_DOMCTL_DEV_RDM_MASK )
>          {
>              ret = -EINVAL;
>              break;
> diff --git a/xen/include/public/domctl.h b/xen/include/public/domctl.h
> index bca25c9..07549a4 100644
> --- a/xen/include/public/domctl.h
> +++ b/xen/include/public/domctl.h
> @@ -480,6 +480,7 @@ struct xen_domctl_assign_device {
>      } u;
>      /* IN */
>  #define XEN_DOMCTL_DEV_RDM_RELAXED      1
> +#define XEN_DOMCTL_DEV_RDM_MASK         0x1

The way this sort of thing is defined in the rest of domctl.h is like this:

#define _XEN_DOMCTL_CDF_hvm_guest     0
#define XEN_DOMCTL_CDF_hvm_guest      (1U<<_XEN_DOMCTL_CDF_hvm_guest)

So the above should be

#define _XEN_DOMCTL_DEV_RDM_RELAXED 0
#define XEN_DOMCTL_DEV_RDM_RELAXED (1U<<_XEN_DOMCTL_DEV_RDM_RELAXED)

And then your check in iommu_do_pci_domctl() would look like

if (flag & ~XEN_DOMCTL_DEV_RDM_RELAXED)

And if we end up adding any extra flags, we just | them into the above
conditional, as is done in, for example, the XEN_DOMCTL_createdomain
case in xen/common/domctl.c:do_domctl().

Thanks,
 -George


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