On Fri, 2013-05-31 at 17:28 +0100, Matthew Garrett wrote: > On Fri, May 31, 2013 at 10:43:49AM -0500, Russ Anderson wrote: > > > When did writing EFI variables to nvram become necessary to boot on > > UEFI? And if it is necessary, why is it that only linux boot loaders > > that use EFI stubs (generally grub2) need it? The current kernel > > boots using EFI/grub and EFI/elilo. It is just when EFI stubs are > > used that the boot fails. > > I think you've misunderstood the problem. If nvram becaomes full, some > systems crash during firmware initialisation. So we can't let nvram > become full. The obvious thing to do here is to look at the values from > QueryVariableInfo, but many systems won't perform any garbage collection > until they're almost out of space and so variables that have been > deleted still show up as used space. We can work around that by adding > up the size of the variables ourselves, but that only gives us the value > for runtime-visible variables. We also need to know how much space is > used by variables that are only visible during boot, hence calling > QueryVariableInfo before ExitBootServices. > > > Which means the previous patch(es) that caused the bricking should > > get pulled, too. > > There are no patches that cause the bricking. This is the description of the original problem: http://www.h-online.com/open/news/item/Booting-Linux-using-UEFI-can-brick-Samsung-laptops-1793958.html And the further investigation: http://mjg59.dreamwidth.org/22855.html If you read the latter, it shows you why we have to use QueryVariableInfo to try to work out how much space we have available. James -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
