[Xen-devel] [PATCH v4] hw/passthrough: Prevent QEMU from mapping PCI option ROM at address 0

[Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>]

The PCI option ROM BAR uses the LSB to indicate if the BAR is enabled.
The AMD graphics driver sets the address bit's of the BAR to 0 but leaves the
LSB set to 1. Whilst this is not good practice, QEMU should be ignoring the
non address parts of the BAR.

This patch adds masking of the bits 0-11 (4k page) parts of the BAR
before comparing the address to 0.

Signed-off-by: Malcolm Crossley <malcolm.crossley@xxxxxxxxxx>
---
 hw/pass-through.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/hw/pass-through.c b/hw/pass-through.c
index 304c438..4c171de 100644
--- a/hw/pass-through.c
+++ b/hw/pass-through.c
@@ -2208,7 +2208,7 @@ static void pt_bar_mapping_one(struct pt_dev *ptdev, int 
bar, int io_enable,
     }
 
     /* prevent guest software mapping memory resource to 00000000h */
-    if ((base->bar_flag == PT_BAR_FLAG_MEM) && (r_addr == 0))
+    if ((base->bar_flag == PT_BAR_FLAG_MEM) && ((r_addr & XC_PAGE_MASK == 0))
         r_addr = -1;
 
     /* align resource size (memory type only) */
-- 
1.7.1


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