mirror of https://github.com/acidanthera/audk.git
a6648418c1
Reference: https://github.com/tianocore/edk2/pull/4892 BmExpandPartitionDevicePath is called to expand "short-form" device paths which are commonly used with OS boot options. To expand a device path, it calls EfiBootManagerConnectAll to connect all the possible BlockIo devices in the system to search for a matching partition. However, this is sometimes unnecessary on certain platforms (such as OVMF/QEMU) because the boot devices are previously explicity connected (See: ConnectDevicesFromQemu). EfiBootManagerConnectAll calls are extremely costly in terms of boot time and resources and should be avoided whenever feasible. ( OVMF call tree: PlatformBootManagerAfterConsole() [OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c] PlatformBdsConnectSequence() [OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c] ConnectDevicesFromQemu() [OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c] ... EfiBootManagerRefreshAllBootOption() [MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c] ... SetBootOrderFromQemu() [OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c] Match() [OvmfPkg/Library/QemuBootOrderLib/QemuBootOrderLib.c] EfiBootManagerGetLoadOptionBuffer() [MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c] BmGetNextLoadOptionBuffer() [MdeModulePkg/Library/UefiBootManagerLib/BmLoadOption.c] BmGetNextLoadOptionDevicePath() [MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c] BmExpandPartitionDevicePath() [MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c] ) Therefore optimize BmExpandPartitionDevicePath to first search the existing BlockIo handles for a match. If a match is not found, then fallback to the original code to call EfiBootManagerConnectAll and search again. Thus, this optimization should be extremely low-risk given the fallback to previous behavior. NOTE: The existing optimization in the code to use a "HDDP" variable to save the last matched device paths does not cover the first time a boot option is expanded (i.e. before the "HDDP" is created) nor when the device configuration has changed (resulting in the boot device moving to a different location in the PCI Bus/Dev hierarchy). This new optimization covers both of these cases on requisite platforms which explicity connect boot devices. In our testing on OVMF/QEMU VMs with dozens of configured vnic devices, these extraneous calls to EfiBootManagerConnectAll from BmExpandPartitionDevicePath were found to cause many seconds (or even minutes) of additional VM boot time in some cases - due to the vnics being unnecessarily connected. Cc: Zhichao Gao zhichao.gao@intel.com Cc: Ray Ni ray.ni@intel.com Signed-off-by: Aaron Young <aaron.young@oracle.com> Message-Id: <20231010150644.37857-1-Aaron.Young@oracle.com> Reviewed-by: Zhichao Gao <zhichao.gao@intel.com> [lersek@redhat.com: add OVMF call tree to commit message] |
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