[Xen-devel] [PATCH v2] vpci: honor read-only devices

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Don't allow the hardware domain write access the PCI config space of
devices marked as read-only.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
Changes since v1:
 - Change the approach and allow full read access, while limiting
   write access to devices marked RO.
---
 xen/drivers/vpci/vpci.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 758d9420e7..fc5feeb627 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -418,13 +418,21 @@ void vpci_write(pci_sbdf_t sbdf, unsigned int reg, 
unsigned int size,
         return;
     }
 
-    /*
-     * Find the PCI dev matching the address.
-     * Passthrough everything that's not trapped.
-     */
+    /* Find the PCI dev matching the address. */
     pdev = pci_get_pdev_by_domain(d, sbdf.seg, sbdf.bus, sbdf.devfn);
     if ( !pdev )
     {
+        const unsigned long *ro_map = pci_get_ro_map(sbdf.seg);
+
+        if ( ro_map && test_bit(sbdf.bdf, ro_map) )
+            /* Ignore writes to read-only devices. */
+            return;
+
+        /*
+         * Let the hardware domain access config space regions for non-existent
+         * devices.
+         * TODO: revisit for domU support.
+         */
         vpci_write_hw(sbdf, reg, size, data);
         return;
     }
-- 
2.22.0


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