On Thu, Nov 26, 2015 at 07:40:10PM +0100, Laszlo Ersek wrote: > On 11/26/15 08:43, Gerd Hoffmann wrote: > > On Di, 2015-11-24 at 11:55 -0500, Cole Robinson wrote: > >> Hi, > >> > >> The UUID seabios reports in its boot output doesn't match what is passed > >> via > >> qemu -uuid option. An example is reported here: > >> > >> https://bugzilla.redhat.com/show_bug.cgi?id=1284259 > >> > >> This is due to: > >> > >> commit caad057bb6ce86a9cb71520af395fd0bd04a659f > >> Author: Eduardo Habkost <ehabk...@redhat.com> > >> Date: Wed Oct 29 11:26:08 2014 -0200 > >> > >> smbios: Encode UUID according to SMBIOS specification > >> > >> Differently from older versions, SMBIOS version 2.6 is explicit about > >> the encoding of UUID fields: > >> > >> > Although RFC 4122 recommends network byte order for all fields, the > >> PC > >> > industry (including the ACPI, UEFI, and Microsoft specifications) has > >> > consistently used little-endian byte encoding for the first three > >> fields: > >> > time_low, time_mid, time_hi_and_version. The same encoding, also > >> known as > >> > wire format, should also be used for the SMBIOS representation of > >> the UUID. > >> > > >> > The UUID {00112233-4455-6677-8899-AABBCCDDEEFF} would thus be > >> represented > >> > as 33 22 11 00 55 44 77 66 88 99 AA BB CC DD EE FF. > >> > >> The dmidecode tool implements this and decodes the above "wire format" > >> when SMBIOS version >= 2.6. We moved from SMBIOS version 2.4 to 2.8 > >> when > >> we started building the SMBIOS entry point inside QEMU, on commit > >> c97294ec1b9e36887e119589d456557d72ab37b5. > >> > >> > >> seabios doesn't seem to handle this special UUID format when reading from > >> smbios. > > > > Hmm. Changing the ordering in display_uuid() is easy. There seems to > > be no easy way to figure which format to use though. Checking the > > version like dmidecode doesn't fly as there are qemu versions with old > > format but version smbios 2.8 in the wild ...
QEMU versions with the old format but smbios 2.8 are buggy, and exposing a broken UUID to guests. I don't believe you need to work around that QEMU bug in the tools that display the UUID. That translates to: * pc-2.2 and later report SMBIOS 2.8 and use the correct format, so it's OK * pc-2.1 is buggy, because it reports SMBIOS 2.8 and use the old format * pc-2.0 and older is OK, because it lets SeaBIOS build the SMBIOS tables, which uses the old format and reports SMBIOS 2.4 Showing the wrong UUID when using pc-2.1 seems unavoidable (because that's a QEMU Bug). But you should be able to display the right UUID on all other pc versions (pc <= 2.0 or pc >= 2.2). > > Plus, because this is guest visible, Eduardo's patch noted above only > changes the encoding for 2.2 and later QEMU machine types. If you run > your reproducer but flip the machine type to 2.1 or earlier, you should > see the UUID on the SeaBIOS screen change. Not 2.1 or earlier, but 2.1 only. If you use 2.0 or earlier, the UUID should be correct. -- Eduardo
