Mistakenly dropped cc list, add again. On 01/01/20 at 11:04am, Dave Young wrote: > Hi Ard, > On 12/31/19 at 12:13pm, Ard Biesheuvel wrote: > > (adding Boris and Dave for the historical perspective) > > > > On Thu, 26 Dec 2019 at 10:55, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote: > > > > > > We carry a quirk in the x86 EFI code to switch back to an older > > > method of mapping the EFI runtime services memory regions, because > > > it was deemed risky at the time to implement a new method without > > > providing a fallback to the old method in case problems arose. > > > > > > Such problems did arise, but they appear to be limited to SGI UV1 > > > machines, and so these are the only ones for which the fallback gets > > > enabled automatically (via a DMI quirk). The fallback can be enabled > > > manually as well, by passing efi=old_map, but there is very little > > > evidence that suggests that this is something that is being relied > > > upon in the field. > > > > > > Given that UV1 support is not enabled by default by the distros > > > (Ubuntu, Fedora), there is no point in carrying this fallback code > > > all the time if there are no other users. So let's refactor it a bit > > > to make it depend on CONFIG_X86_UV, and remove the ability to enable > > > it by hand. > > > > > > Cc: Dimitri Sivanich <dimitri.sivanich@xxxxxxx> > > > Cc: Mike Travis <mike.travis@xxxxxxx> > > > Cc: Hedi Berriche <hedi.berriche@xxxxxxx> > > > Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> > > > > Boris, since you were the one that added efi=old_map: do you know of > > any cases beyond SGI UV1 where it was actually needed? There is some > > mention of using it to work around transient breakage on 32-bit caused > > by your original changes, but other than that, Google doesn't seem to > > know about any cases where efi=old_map is being used to deal with > > actual firmware quirks. > > > > As a followup to this change, I'd like to move the old memmap handling > > into the UV1 support code, so it is omitted unless UV support is > > compiled it, and so it can be retired with the rest of it once that > > time comes. > > > > I also only know about the SGI UV1 quirk, and I'm not sure about > if this affects some 32bit user, otherwise it should be a good idea > As for the 32bit I remember Sai previously did use old_map for kexecing. > Added Sai in cc for thoughts. > > Thanks > Dave
