On Wed, Jun 08, 2016 at 01:36:23PM +0100, Matt Fleming wrote: > (Cc'ing people familiar with e820 map woes) > > On Thu, 02 Jun, at 03:50:35PM, Joseph Thelen wrote: > > Currently, the EFI memory map entries are disabled by default and must > > be enabled by passing the kernel boot option: > > > > add_efi_memmap > > > > The EFI memory map entries should be enabled on systems with more > > than 128 E820 entries, which includes many UV systems. Check if > > we're on a UV system by chekcing the uv system table. > > Enable the EFI memory map entries if we're on a UV system. > > > > This change is backward compatible because the EFI memory map entries are > > still disabled by default on non-UV systems, and it maintains the previous > > behavior of the kernel boot option. In addition, it allows the EFI memory > > map entries to be explicitly disabled (will not be automatically enabled) > > by setting the add_efi_memmap boot option to anything that kstringtobool > > will determine to be false. > > > > Signed-off-by: Joseph Thelen <jthelen@xxxxxxx> > > Cc: Alex Thorlton <athorlton@xxxxxxx> > > Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > > Cc: x86@xxxxxxxxxx > > Cc: linux-efi@xxxxxxxxxxxxxxx > > --- > > arch/x86/platform/efi/efi.c | 43 +++++++++++++++++++++++++++++++++++++++---- > > 1 file changed, 39 insertions(+), 4 deletions(-) > > What's the ultimate goal here? To not require that users specify the > add_efi_memmap kernel parameter in the future? Presumably they do > today? > > FYI, a lot of non-UV systems have more than 128 entries and the way we > handle it is by using the SETUP_E820_EXT setup_data entry in > boot_params in the EFI boot stub (I don't think boot loaders use it > because they largely go via the stub anyhow). > > So if you've got control over your boot loader, and assuming SGI UV > systems don't boot using the EFI boot stub, you could look at adding > boot loader support for SETUP_E820_EXT to force enable > 128 entries > automatically without any new kernel code. We're still reasonably confident we'll need something like this. Although, after looking into the stuff you mention, it seems that it should perhaps be a bit more sophisticated than just checking if we're on a UV system. We'll get back to you after digging into this a bit more and coming up with some more specific reasons for the change. Thanks, Joseph Thelen -- 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
