[Xen-devel] [PATCH v3] 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 v2:
 - Fix test harness.
 - Do the RO check before the ownership one.

Changes since v1:
 - Change the approach and allow full read access, while limiting
   write access to devices marked RO.
---
 tools/tests/vpci/emul.h | 3 +++
 xen/drivers/vpci/vpci.c | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/tools/tests/vpci/emul.h b/tools/tests/vpci/emul.h
index 5d47544bf7..2e1d3057c9 100644
--- a/tools/tests/vpci/emul.h
+++ b/tools/tests/vpci/emul.h
@@ -92,6 +92,9 @@ typedef union {
 #define xfree(p) free(p)
 
 #define pci_get_pdev_by_domain(...) &test_pdev
+#define pci_get_ro_map(...) NULL
+
+#define test_bit(...) false
 
 /* Dummy native helpers. Writes are ignored, reads return 1's. */
 #define pci_conf_read8(...)     0xff
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 758d9420e7..cbd1bac7fc 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -411,6 +411,7 @@ void vpci_write(pci_sbdf_t sbdf, unsigned int reg, unsigned 
int size,
     const struct pci_dev *pdev;
     const struct vpci_register *r;
     unsigned int data_offset = 0;
+    const unsigned long *ro_map = pci_get_ro_map(sbdf.seg);
 
     if ( !size )
     {
@@ -418,6 +419,10 @@ void vpci_write(pci_sbdf_t sbdf, unsigned int reg, 
unsigned int size,
         return;
     }
 
+    if ( ro_map && test_bit(sbdf.bdf, ro_map) )
+        /* Ignore writes to read-only devices. */
+        return;
+
     /*
      * Find the PCI dev matching the address.
      * Passthrough everything that's not trapped.
-- 
2.22.0


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