[PATCH 2/2] xen-pciback: Allow enabling/disabling expansion ROM

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

From: Dwayne Litzenberger <dlitz@dlitz.net>

Newer AMD GPUs store their initialization routines as bytecode on the
ROM.  This fixes the following initialization error inside the VM when
doing PCI passthrough:

    radeon 0000:00:05.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff
    radeon 0000:00:05.0: Invalid PCI ROM header signature: expecting 0xaa55, got 0xffff
    [drm:radeon_get_bios [radeon]] *ERROR* Unable to locate a BIOS ROM
    radeon 0000:00:05.0: Fatal error during GPU init

Signed-off-by: Dwayne Litzenberger <dlitz@dlitz.net>
---
 drivers/xen/xen-pciback/conf_space_header.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/xen/xen-pciback/conf_space_header.c b/drivers/xen/xen-pciback/conf_space_header.c
index 697d0a8..bc145d3 100644
--- a/drivers/xen/xen-pciback/conf_space_header.c
+++ b/drivers/xen/xen-pciback/conf_space_header.c
@@ -150,21 +150,21 @@ static int rom_write(struct pci_dev *dev, int offset, u32 value, void *data)
 	if ((value | ~PCI_ROM_ADDRESS_MASK) == ~0U)
 		bar->which = 1;
 	else {
-		u32 tmpval;
-		err = pci_read_config_dword(dev, offset, &tmpval);
+		u32 newval = bar->val;
+
+		/* Allow enabling/disabling rom, if present */
+		if (newval & PCI_ROM_ADDRESS_MASK) {
+			newval &= ~PCI_ROM_ADDRESS_ENABLE;
+			newval |= value & PCI_ROM_ADDRESS_ENABLE;
+		}
+
+		err = pci_write_config_dword(dev, offset, newval);
 		if (err)
 			goto out;
-		if (tmpval != bar->val && value == bar->val) {
-			/* Allow restoration of bar value. */
-			err = pci_write_config_dword(dev, offset, bar->val);
-			if (err)
-				goto out;
-		}
+		bar->val = newval;
 		bar->which = 0;
 	}
 
-	/* Do we need to support enabling/disabling the rom address here? */
-
 out:
 	return err;
 }
-- 
git-series 0.9.1