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Re: [PATCH RFC] vPCI: account for hidden devices in modify_bars()

Hello, Jan!

On 30.08.21 16:04, Jan Beulich wrote:
Hidden devices (e.g. an add-in PCI serial card used for Xen's serial
console) are associated with DomXEN, not Dom0. This means that while
looking for overlapping BARs such devices cannot be found on Dom0's
list of devices; DomXEN's list also needs to be scanned.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
RFC: Patch intentionally mis-formatted, as the necessary re-indentation
      would make the diff difficult to read. At this point I'd merely
      like to gather input towards possible better approaches to solve
      the issue (not the least because quite possibly there are further
      places needing changing).

--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -206,6 +206,7 @@ static int modify_bars(const struct pci_
      struct vpci_header *header = &pdev->vpci->header;
      struct rangeset *mem = rangeset_new(NULL, NULL, 0);
      struct pci_dev *tmp, *dev = NULL;
+    const struct domain *d;
      const struct vpci_msix *msix = pdev->vpci->msix;
      unsigned int i;
      int rc;
@@ -265,7 +266,8 @@ static int modify_bars(const struct pci_
       * Check for overlaps with other BARs. Note that only BARs that are
       * currently mapped (enabled) are checked for overlaps.
-    for_each_pdev ( pdev->domain, tmp )
+for ( d = pdev->domain; ; d = dom_xen ) {//todo

I am not quite sure this will be correct for the cases where pdev->domain != 

e.g. in the series for PCI passthrough for Arm this can be any guest. For such 

we'll force running the loop for dom_xen which I am not sure is desirable.

Another question is why such a hidden device has its pdev->domain not set 

so we need to work this around?

Thank you,


+    for_each_pdev ( d, tmp )
          if ( tmp == pdev )
@@ -282,6 +284,7 @@ static int modify_bars(const struct pci_
+if ( !tmp->vpci ) { ASSERT(d == dom_xen && system_state < SYS_STATE_active); 
continue; }//todo
for ( i = 0; i < ARRAY_SIZE(tmp->vpci->header.bars); i++ )
@@ -308,6 +311,7 @@ static int modify_bars(const struct pci_
+if ( !is_hardware_domain(d) ) break; }//todo



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