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Re: [Xen-devel] [v7][RFC][PATCH 06/13] hvmloader/ram: check if guest memory is out of reserved device memory maps



On 2014/11/12 16:55, Jan Beulich wrote:
On 12.11.14 at 04:05, <tiejun.chen@xxxxxxxxx> wrote:
I don't see any feedback to this point, so I think you still prefer we
should do all check in the callback function.

As a draft this looks reasonable, but there are various bugs to be
dealt with along with cosmetic issues (I'll point out the former, but
I'm tired of pointing out the latter once again - please go back to
earlier reviews of patches to refresh e.g. what types to use for
loop variables).

I tried to address this but obviously we have to pass each 'pdf' to
callback functions,

Yes, but at the generic IOMMU layer this shouldn't be named "bdf",
but something more neutral (maybe "id"). And you again lost the
segment there.

@@ -36,9 +40,24 @@ static int get_reserved_device_memory(xen_pfn_t start,
           if ( rdm.start_pfn != start || rdm.nr_pages != nr )
               return -ERANGE;

-        if ( __copy_to_compat_offset(grdm->map.buffer, grdm->used_entries,
-                                     &rdm, 1) )
-            return -EFAULT;
+        if ( d->arch.hvm_domain.pci_force )
+        {
+            if ( __copy_to_compat_offset(grdm->map.buffer, grdm->used_entries,
+                                         &rdm, 1) )
+                return -EFAULT;
+        }
+        else
+        {
+            for ( i = 0; i < d->arch.hvm_domain.num_pcidevs; i++ )
+            {
+                pt_bdf = PCI_BDF2(d->arch.hvm_domain.pcidevs[i].bus,
+                                  d->arch.hvm_domain.pcidevs[i].devfn);
+                if ( pt_bdf == bdf )
+                    if ( __copy_to_compat_offset(grdm->map.buffer, 
grdm->used_entries,
+                                                 &rdm, 1) )
+                        return -EFAULT;

I think d->arch.hvm_domain.pcidevs[] shouldn't contain duplicates,
and hence there's no point continuing the loop if you found a match.


I take a look at this again. Seems we shouldn't just check bdf since as you know its possible to occupy one entry by multiple different BDFs, so we have to filter-to-keep one entry. Instead, I really hope we'd check to expose before we do the hypercall.

BTW, I already ping Yang in local to look that possibility to reorder the sequence of the device assignment and the memory population in iommu side.

Thanks
Tiejun

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