MdeModulePkg: Optimize BmExpandPartitionDevicePath to avoid ConnectAll #4892
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BmExpandPartitionDevicePath calls EfiBootManagerConnectAll to expand "short form" device paths - which are commonly used with OS boot options. However on some platforms (such as OVMF/QEMU), this ConnectAll call is often unnecessary as the BlockIo handles have already been created by prior explicit boot device connection. ConnectAll calls are very costly and should be avoided whenever feasible. So, optimze the code to first search the existing BlockIo handles for a match. If no match is found, then fallback to do a ConnectAll and search again. NOTE: the existing optimization in the code - to use a "HDDP" variable to store the last matching device path - doesn't cover the first time a device path is expanded nor when a boot device's location changes. In both of these cases, a ConnectAll call is still made from BmExpandPartitionDevicePath. This new optimization fixes both of these cases on requisite platforms. Signed-off-by: Aaron Young <aaron.young@oracle.com>
lersek
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Reference: tianocore#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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personal CI run; superseded by #4948 |
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Reference: #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]
mdkinney
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Reference: tianocore/edk2#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]
mdkinney
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Reference: tianocore/edk2#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]
mdkinney
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Reference: tianocore/edk2#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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Reference: tianocore/edk2#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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Reference: tianocore/edk2#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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Reference: tianocore/edk2#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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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 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.
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 appearing at a different PCI Bus/Dev). This new optimization covers both of these cases on requisite platforms which explicity connect boot devices (e.g. OVMF/QEMU).
In our testing on OVMF/QEMU VMs with dozens of configured vnic devices, these extraneous calls to EfiBootManagerConnectAll from BmExpandPartitionDevicePath were found to cause 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