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@gmail.com
--- 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