On Wed, Dec 04, 2013 at 03:06:47PM -0600, Matt Sealey wrote: > By the time we get half-way through arm/kernel/head.S the cache and > MMU has been turned off and on and off again by the decompressor, and > after a large amount of guesswork and arbitrary restriction-based > implementation, there's no guarantee that the kernel hasn't been > decompressed over some important UEFI feature or some memory hasn't > been trashed. You can't make that guarantee because by entering the > plain zImage, you forfeited that information. This is at worst case > going to be lots of blank screens and blinking serial console prompts > and little more than frustration.. So, Grant covered the reason _why_ we coexist with zImage, so I won't go into that. I will however point out that we are explicitly using the UEFI interfaces to allocate the regions the zImage will decompress into. This isn't guesswork, and has in fact already turned up issues with a couple of UEFI board ports that reserved memory near 0 (which were indeed previously being silently overwritten by the kernel decompression). We _are_ planning to do more development for subsequent patches, making more use of the UEFI memory map. And by subsequent, I mean hopefully in time for 3.14. I sneekily included this in the version of uefi.txt sent out for separate review early November: http://permalink.gmane.org/gmane.linux.kernel.efi/2657, but not in the one included with this patch set (since the code isn't there yet). But we considered it more important to get the basic support ready first. At that point, you will see the stub reading the dram_base from the UEFI memory map rather than DT, and memblock_init getting its input from there too. Regards, Leif -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
