On Fri, May 31, 2013 at 05:57:31PM -0500, Russ Anderson wrote: > On Fri, May 31, 2013 at 05:28:16PM +0100, Matthew Garrett wrote: > > 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. > > OK. I get nvram looks full due to lack of garbage collection > on some systems. Does QueryVariableInfo (at runtime) tell you > it is full? Is the problem that it says it is full when it > is not, or does not tell you it is full when it is? QueryVariableInfo reports the amount used *including garbage*. This makes it useless for determining how much space is available for the firmware to use. > > 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, > > Is it valid to assume that only the kernel writes to nvram at > runtime? Can bios log error information to nvram on an SMM > interrupt (for example)? There's a limited number of situations where the firmware can write to nvram, but they're basically uninteresting. Practically speaking, it's always via the kernel once ExitBootServices() has been called. > > hence calling > > QueryVariableInfo before ExitBootServices. > > Correct me if I am wrong, but that is called from EFI stubs, > which is only used by some bootloaders (sometimes grub2). > Does that mean EFI/grub and EFI/elilo will not hit the problem, > or will not have your fix? Will not have the fix. Boot EFI systems via the EFI stub. -- Matthew Garrett | mjg59@xxxxxxxxxxxxx -- 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
