On 05/20/15 05:29, lidonglin wrote: > Hi all： > I want to know what's the differece between FD_SIZE_1MB and > FD_SIZE_2MB. For example, I build release ovmf whose size is 1MB > default. It can work. That's just as I should be. And I build release > ovmf with additional parameter -D FD_SIZE_2MB. It also can work. Who > can explain the difference between them?
The difference between the two flags is that the various firmware volumes, and the final flash device image that contains them, accordingly, will have twice as much room with FD_SIZE_2MB than with FD_SIZE_1MB. The double room is / may be necessary due to various build-time decisions, such as: - "-b DEBUG" vs. "-b RELEASE" -- driver binaries are larger when built for DEBUG, - "-a IA32 -p OvmfPkg/OvmfPkgIa32.dsc" vs. "-a IA32 -a X64 -p OvmfPkg/OvmfPkgIa32X64.ds" vs. "-a X64 -p OvmfPkg/OvmfPkgX64.dsc" -- 64-bit binaries are larger than 32-bit binaries, - build time feature flags: "-D SOURCE_DEBUG_ENABLE", "-D SECURE_BOOT_ENABLE", "-D NETWORK_IP6_ENABLE", "-D CSM_ENABLE", etc -- additional features imply additional drivers and libraries, taking up more space. So, the only reasonable *form* I can imagine for your question is: "why would I want the 1MB size flash device image, rather than the 2MB one, ever?" The answer is, "you wouldn't". I don't remember why we still make the 1MB flash device image size the default under some circumstances -- probably out of basic frugality. Historically, only the 1MB FD size had been supported. Occasionally it proved too little -- as the features listed above were being introduced and were simultaneously enabled at build time, we sometimes ran out of space in the firmware volumes. So a decision was made to allow a 2MB FD size, but we didn't change the default (for all configs) at once. (You can run "git blame" and "git log" on the FDF files...) Personally, I never bother to build (except maybe for testing the build itself) with "-b RELEASE", which implies that all my builds end up with a 2MB FD size. If you'd like to understand the details of the FD structure, please see: - EDK II FDF File Spec http://tianocore.sourceforge.net/wiki/EDK_II_Specifications - OvmfPkg/OvmfPkg.fdf.inc, - OvmfPkg/OvmfPkg*.fdf (any one of those will be sufficient to look at), - section "Firmware image structure" in http://www.linux-kvm.org/downloads/lersek/ovmf-whitepaper-c770f8c.txt Thanks Laszlo > > > ------------------------------------------------------------------------------ > One dashboard for servers and applications across Physical-Virtual-Cloud > Widest out-of-the-box monitoring support with 50+ applications > Performance metrics, stats and reports that give you Actionable Insights > Deep dive visibility with transaction tracing using APM Insight. > http://ad.doubleclick.net/ddm/clk/290420510;117567292;y > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/edk2-devel > ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ edk2-devel mailing list edk2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/edk2-devel
