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Re: [Xen-devel] [v3][PATCH 04/16] xen/passthrough: extend hypercall to support rdm reservation policy



On 2015/6/18 15:53, Jan Beulich wrote:
On 18.06.15 at 09:14, <tiejun.chen@xxxxxxxxx> wrote:
On 2015/6/17 18:11, Jan Beulich wrote:
On 11.06.15 at 03:15, <tiejun.chen@xxxxxxxxx> wrote:
@@ -1577,9 +1578,10 @@ 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;

           ret = device_assigned(seg, bus, devfn) ?:
-              assign_device(d, seg, bus, devfn);
+              assign_device(d, seg, bus, devfn, flag);

I think you should range check the flag passed to make future
extensions possible (and to avoid ambiguity on what out of
range values would mean).

Yeah.

Maybe I can set this comment,

      /* Make sure this is always the last. */

#define XEN_DOMCTL_DEV_NO_RDM           2

      uint32_t  flag;   /* flag of assigned device */

Why would you want to needlessly break the interface is a new
constant gets added? It's a domctl, so it can be changed, but we
shouldn't change for no reason.

I just think XEN_DOMCTL_DEV_NO_RDM is prone to represent a sort of ending of all flags, and I also add this comment,

/* Make sure this is always the last. */


and then

          flag = domctl->u.assign_device.flag;
          if ( flag > XEN_DOMCTL_DEV_NO_RDM )

All that needs updating when a new constant gets added is this
line.

This place really isn't one spotlight to take a attention when a new flag is introduced, right? So what I intend to is trying to make sure we don't need to change this.


          {
              printk(XENLOG_G_ERR "XEN_DOMCTL_assign_device: "
                     "assign %04x:%02x:%02x.%u to dom%d failed "
                     "with unknown rdm flag %x. (%d)\n",
                     seg, bus, PCI_SLOT(devfn), PCI_FUNC(devfn),
                     d->domain_id, flag, ret);

I see absolutely no reason for such a log message.


Do you mean I should simplify this log message? Or remove completely?

Thanks
Tiejun

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