----- Original Message ----- > From: "Laszlo Ersek" <[email protected]> > To: "spam collector" <[email protected]> > Cc: [email protected] > Sent: Tuesday, October 4, 2016 10:22:34 AM > Subject: Re: [edk2] OVMF.fd and placement of EfiBootServicesData > > On 10/04/16 18:39, spam collector wrote: > > > [...] I was surprised to see that QEMU and/or > > OVMF requires the NvVars file to exist on the partition, else OVMF > > does not even show the shell, even on a perfectly valid partitioned > > image. I don't know if this is QEMU's fault or OVMF's fault. If > > the NvVars file does not exist, is it the desired option to fail > > the loading of the shell? If the file does not exist, can OVMF use > > default values and still load the shell? > > OVMF does not require the NvVars file to exist. The NvVars file is only > used / relied on when the QEMU command line is incorrect, that is, when > it does not configure the pflash chip(s) for storing the firmware binary > and/or the variable store. > > * The command line that you are likely used to goes like this: > > qemu-system-x86_64 -bios OVMF.fd ...
Yes. I am currently using that line with the only modification of the 32-bit emulation on both parts. > This is broken. Don't use it. The OVMF.fd file in the above usage is a > unified file (1MB or 2MB in size), containing both the firmware binary > and an empty (pre-formatted) variable store. The entire file is mapped > into guest memory as ROM. The variable store area is not writeable, > hence OVMF falls back to the NvVars based emulation. That emulation is > not entirely compatible with the UEFI spec. Don't use the above command > line. > > * The first stage improvement is the following command line: > > qemu-system-x86_64 -pflash OVMF.fd This did not work either with or without the NvVars file present. > The OVMF.fd file has the same characteristics as above, but the same > stuff is mapped as a programmable pflash chip into guest memory. It > means that the guest memory area in question *normally* reads and > executes like normal RAM, but if you write to it (that is, if OVMF's > flash driver writes to it), it is flipped into "programming mode", where > you can read and write the device using various "commands". One of those > commands flips the device back to "normal" mode. > > In this mode, the NvVars-based emulation is not used, and the variable > store / variable services will work as defined by the UEFI spec. > > The problem with this approach is that the OVMF.fd file contains both a > firmware binary and a live variable store. You cannot upgrade the > firmware binary without losing the VM's long-term, non-volatile variables. > > * The second stage improvement is the following command line: > > # create the virtual machine's private variable store from the > # pristine variable store template, if the former doesn't exist yet, > # or has been lost for some reason > if ! [ -e GUEST_1_VARS.fd ]; then > cp OVMF_VARS.fd GUEST_1_VARS.fd > fi > > qemu-system-x86_64 \ > -drive if=pflash,format=raw,unit=0,readonly,file=OVMF_CODE.fd \ > -drive if=pflash,format=raw,unit=1,file=GUEST_1_VARS.fd \ > ... > > In this case, the OVMF_CODE.fd and OVMF_VARS.fd are used separately. > (You can find both files under the Build directory; plus Gerd Hoffmann's > RPM files <https://www.kraxel.org/repos/> also package them.) For the life of me I could not find any directory called "Build". I did find a few RPM files and one of them contained: OVMF_CODE-pure-efi.fd and OVMF_VARS-pure-efi.fd However, no matter the emulation (32- or 64-bit), neither worked and would get as far as printing the '.' just before the .FLOPPY failed .CD-ROM failed etc. lines and go no further. Thank you for the excellent description, however sorry for my ignorance. If you don't mind, would you please specify a specific URL that contains the two files you speak of, whether it be a listing of those files, a .gz file, or even a .rpm file. Thank you, Ben _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
