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[pci] Use runtime selectable PCI I/O API for EFI cloud builds

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On some systems (observed on an AWS m8g.medium instance in eu-west-2),
the UEFI firmware omits the PCI host bridge drivers for all but the
first PCI bus.  The observable result is that any devices on other PCI
buses (such as the ENA network device) are not enumerated by the UEFI
firmware and are therefore unusable by iPXE.

Support these systems by switching to using PCIAPI_CLOUD for EFI cloud
builds, trying the EFI PCI I/O API first and falling back to direct
access (via ECAM) for devices that the UEFI firmware has failed to
enumerate itself.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-11-24 20:27:53 +00:00
parent 9c1ac48bcf
commit dfea3bbfad
4 changed files with 18 additions and 3 deletions
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7
src/include/ipxe/pci_io.h
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@@ -192,9 +192,10 @@ struct pci_api {
#endif
/* PCI runtime selectable API priorities */
#define PCIAPI_PRIORITY_ECAM 01 /**< ACPI ECAM */
#define PCIAPI_PRIORITY_PCBIOS 02 /**< PCI BIOS calls */
#define PCIAPI_PRIORITY_DIRECT 03 /**< Direct Type 1 accesses */
#define PCIAPI_PRIORITY_EFI 01 /**< EFI PCI I/O protocols */
#define PCIAPI_PRIORITY_ECAM 02 /**< ACPI ECAM */
#define PCIAPI_PRIORITY_PCBIOS 03 /**< PCI BIOS calls */
#define PCIAPI_PRIORITY_DIRECT 04 /**< Direct Type 1 accesses */
/** Provide a runtime selectable PCI I/O API */
#define PROVIDE_PCIAPI_RUNTIME( subsys, priority ) \