On 09/19/16 17:00, Saqib Khan wrote: > Hello all, this is my first post to this list and i am very new to edk2 > development. > > I started by building BootManagerMenuApp with following functionality > > - Boot from BootManagerManueApp > - Run an Helloworld EFI > - Run windows 7 EFI to boot windows 7 > > Now i want to develop an EFI which will first run Helloworld EFI then it > will boot windows 7 which is installed on legacy boot (NOT EFI). > > I have looked through http://bluestop.org/edk2/docs/trunk/ documentation > thoroughly but i am not able to get any thing for legacy boot from an EFI. > > > It will be helpful if someone guide me the flow for legacy booting from an > EFI .
You can add your EFI application to a SysPrep#### load option, then the legacy-booted Windows OS to a normal Boot#### load option. See "3.1.7 Required System Preparation Applications" in the UEFI-2.6 spec, about the ordering between SysPrep#### and Boot####. Furthermore, legacy boot can be triggered by using a BBS (BIOS Boot Specification) device path in the Boot#### option. This devpath node type is documented in UEFI-2.6 "Table 98. Device Node Table", and in the Compatibility Support Module Specification, rev 0.98, "3.2.1 Legacy BIOS Protocol", near BBS_BBS_DEVICE_PATH. For legacy boot to work, your platform firmware must of course include a Compatibility Support Module. As an example platform, SeaBIOS can be built as a CSM, then embedded into OVMF with the -D CSM_ENABLE build switch. (Grep OvmfPkg/OvmfPkg*.{dsc,fdf} for CSM_ENABLE.) Specifically for Windows 7 though, you don't need a full CSM in order to boot it under UEFI. You can boot it in UEFI mode just fine, as long as you have some VBE services installed in the C segment. Windows 7 will run those functions in its internal real-mode emulator, for setting up the display: https://en.wikipedia.org/wiki/Virtual_DOS_machine That is, the VBE functions will not be executed natively, they will be interpreted / emulated. We utilized this fact for booting UEFI Windows 7 without a CSM on QEMU, on the virtual QXL video card; see OvmfPkg/QemuVideoDxe/VbeShim.*. Thanks Laszlo _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel