On Sun, Jan 12, 2020 at 03:00:53PM +0200, Jari Ruusu wrote: > Intel Software Developer's Manual, volume 3, chapter 9.11.6 says: > "Note that the microcode update must be aligned on a 16-byte > boundary and the size of the microcode update must be 1-KByte > granular" > > When early-load Intel microcode is loaded from initramfs, > userspace tool 'iucode_tool' has already 16-byte aligned those > microcode bits in that initramfs image. Image that was created > something like this: > > iucode_tool --write-earlyfw=FOO.cpio microcode-files... > > However, when early-load Intel microcode is loaded from built-in > firmware BLOB using CONFIG_EXTRA_FIRMWARE= kernel config option, > that 16-byte alignment is not guaranteed. Thanks for the patch! So what happens with you use the built-in firmware loader for the Intel microcode at this time? I am surprised this issue wasn't reported earlier, so thanks for picking it up, but to be complete such a change requires a bit more information. What exactly happens now? > Fix this by forcing all built-in firmware BLOBs to 16-byte > alignment. That's a huge stretch, see below. > Signed-off-by: Jari Ruusu <jari.ruusu@xxxxxxxxx> > > --- a/drivers/base/firmware_loader/builtin/Makefile > +++ b/drivers/base/firmware_loader/builtin/Makefile > @@ -17,7 +17,7 @@ > filechk_fwbin = \ > echo "/* Generated by $(src)/Makefile */" ;\ > echo " .section .rodata" ;\ > - echo " .p2align $(ASM_ALIGN)" ;\ > + echo " .p2align 4" ;\ You are forcing 16 byte alignment to *all* built-in firmware, and some architectures may have a different requirement. If things used to work with ASM_ALIGN which is a construct only used for this code, but your change fixes it with Intel microcode loading -- it however *may* break things for other built-in firmware used. In particular if you note above it used to align things to 2^3 so 8 bytes if on CONFIG_64BIT, otherwise things get aligned to 2^2 so 4 bytes. So I'd like to determine first if we really need this. Then if so, either add a new global config option, and worst comes to worst figure out a way to do it per driver. I don't think we'd need it per driver. If set as a global new config option, we can use the same logic and allow an architecture override if the user / architecture kconfig configures it such: config ARCH_DEFAULT_FIRMWARE_ALIGNMENT string "Default architecture firmware aligmnent" "4" if 64BIT "3" if !64BIT config FIRMWARE_BUILTIN_ALIGN string "Built in firmware aligment requirement" default ARCH_DEFAULT_FIRMWARE_ALIGNMENT if !ARCH_CUSTOM_FIRMWARE_ALIGNMENT default ARCH_CUSTOM_FIRMWARE_ALIGNMENT_VAL if ARCH_CUSTOM_FIRMWARE_ALIGNMENT Some good description goes here Or something like that. Luis
