[efi] Enumerate PCI BARs in same order as SnpDxe

The UEFI specification has an implicit and demonstrably incorrect requirement (in the Mem_IO() calling convention) that any UNDI network device has at most one memory BAR and one I/O BAR. Some UEFI platforms have been observed to report the existence of non-existent additional I/O BARs, causing iPXE to select the wrong BAR. This problem does not affect the SnpDxe driver, since that driver will always choose the lowest numbered existent BAR of each type. Adjust iPXE's behaviour to match that of SnpDxe, i.e. to always select the lowest numbered BAR(s). Debugged-by: Andreas Hammarskjöld <junior@2PintSoftware.com> Debugged-by: Adklei <adklei@realtek.com> Signed-off-by: Michael Brown <mcb30@ipxe.org>
ipxe · Jul 21, 2017 · 9ccd8fe · 9ccd8fe
1 parent 0600d3a
commit 9ccd8fe
Showing 1 changed file with 2 additions and 2 deletions.
diff --git a/src/drivers/net/efi/nii.c b/src/drivers/net/efi/nii.c
@@ -202,7 +202,7 @@ static int nii_pci_open ( struct nii_nic *nii ) {
 		EFI_ACPI_ADDRESS_SPACE_DESCRIPTOR *acpi;
 		void *resource;
 	} desc;
-	unsigned int bar;
+	int bar;
 	EFI_STATUS efirc;
 	int rc;
 
@@ -230,7 +230,7 @@ static int nii_pci_open ( struct nii_nic *nii ) {
 	/* Identify memory and I/O BARs */
 	nii->mem_bar = PCI_MAX_BAR;
 	nii->io_bar = PCI_MAX_BAR;
-	for ( bar = 0 ; bar < PCI_MAX_BAR ; bar++ ) {
+	for ( bar = ( PCI_MAX_BAR - 1 ) ; bar >= 0 ; bar-- ) {
 		efirc = nii->pci_io->GetBarAttributes ( nii->pci_io, bar, NULL,
 							&desc.resource );
 		if ( efirc == EFI_UNSUPPORTED ) {