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[pci] Avoid scanning nonexistent buses when using PCIAPI_DIRECT 

There is no method for obtaining the number of PCI buses when using
PCIAPI_DIRECT, and we therefore currently scan all possible bus
numbers.  This can cause a several-second startup delay in some
virtualised environments, since PCI configuration space access will
necessarily require the involvement of the hypervisor.

Ameliorate this situation by defaulting to scanning only a single bus,
and expanding the number of PCI buses to accommodate any subordinate
buses that are detected during enumeration.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/329/head
Michael Brown 2021-04-10 13:14:30 +01:00
parent c0346dbb49
commit 0be8491b71
3 changed files with 30 additions and 4 deletions
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4
src/arch/x86/include/ipxe/pcidirect.h
View File

@ -32,8 +32,8 @@ extern void pcidirect_prepare ( struct pci_device *pci, int where );
*/
static inline __always_inline int
PCIAPI_INLINE ( direct, pci_num_bus ) ( void ) {
/* No way to work this out via Type 1 accesses */
return 0x100;
/* Scan first bus and rely on bridge detection to find higher buses */
return 1;
}
/**

27
src/drivers/bus/pci.c
View File

@ -228,6 +228,9 @@ int pci_read_config ( struct pci_device *pci ) {
*/
int pci_find_next ( struct pci_device *pci, unsigned int busdevfn ) {
static unsigned int end;
unsigned int sub_end;
uint8_t hdrtype;
uint8_t sub;
int rc;
/* Determine number of PCI buses */
@ -236,10 +239,30 @@ int pci_find_next ( struct pci_device *pci, unsigned int busdevfn ) {
/* Find next PCI device, if any */
for ( ; busdevfn < end ; busdevfn++ ) {
/* Check for PCI device existence */
memset ( pci, 0, sizeof ( *pci ) );
pci_init ( pci, busdevfn );
if ( ( rc = pci_read_config ( pci ) ) == 0 )
return busdevfn;
if ( ( rc = pci_read_config ( pci ) ) != 0 )
continue;
/* If device is a bridge, expand the number of PCI
* buses as needed.
*/
pci_read_config_byte ( pci, PCI_HEADER_TYPE, &hdrtype );
hdrtype &= PCI_HEADER_TYPE_MASK;
if ( hdrtype == PCI_HEADER_TYPE_BRIDGE ) {
pci_read_config_byte ( pci, PCI_SUBORDINATE, &sub );
sub_end = PCI_BUSDEVFN ( 0, ( sub + 1 ), 0, 0 );
if ( end < sub_end ) {
DBGC ( pci, PCI_FMT " found subordinate bus "
"%#02x\n", PCI_ARGS ( pci ), sub );
end = sub_end;
}
}
/* Return this device */
return busdevfn;
}
return -ENODEV;

3
src/include/ipxe/pci.h
View File

@ -135,6 +135,9 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#define PCI_CLASS_SERIAL_USB_EHCI 0x20 /**< ECHI USB controller */
#define PCI_CLASS_SERIAL_USB_XHCI 0x30 /**< xHCI USB controller */
/** Subordinate bus number */
#define PCI_SUBORDINATE 0x1a
/** Construct PCI class
*
* @v base Base class (or PCI_ANY_ID)