[Qemu-devel] [PATCH v2] Align PCI capabilities in pci_find_space

[mjr@cs.wisc.edu]

From: Matt Renzelmann <mjr@cs.wisc.edu>

The current implementation of pci_find_space does not correctly align
PCI capabilities in the PCI configuration space.  This patch fixes
this issue.

Signed-off-by: Matt Renzelmann <mjr@cs.wisc.edu>
---

Alex Williamson <alex.williamson@redhat.com> wrote:
> I think you could just search every 4th byte.  In fact, this whole used
> byte-map could be turned into a single uint64_t bitmap for standard
> config space.  Thanks,

I've not tested this version of the patch, in contrast to the last, so
I'm a bit less confident of its correctness.  I did not reimplement it
as suggested as I'm not that familiar with this code, and instead just
applied the every 4th byte strategy.

 hw/pci.c |   12 ++++++++----
 1 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/hw/pci.c b/hw/pci.c
index f855cf3..e99866a 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -1631,11 +1631,15 @@ static int pci_find_space(PCIDevice *pdev, uint8_t size)
     int config_size = pci_config_size(pdev);
     int offset = PCI_CONFIG_HEADER_SIZE;
     int i;
-    for (i = PCI_CONFIG_HEADER_SIZE; i < config_size; ++i)
-        if (pdev->used[i])
-            offset = i + 1;
-        else if (i - offset + 1 == size)
+
+    for (i = PCI_CONFIG_HEADER_SIZE; i < config_size; i += 4) {
+        if (pdev->used[i]) {
+            offset = i + 4;
+        } else if (i - offset + 1 == size) {
             return offset;
+        }
+    }
+
     return 0;
 }
 
-- 
1.7.5.4