Re: [PATCH v8 00/23] efi/x86: Avoid bare metal decompressor during EFI boot

Ard Biesheuvel
2023-08-05T17:37:37Z

On Sat, 5 Aug 2023 at 16:41, Borislav Petkov <bp@alien8.de> wrote:
>
> On Wed, Aug 02, 2023 at 05:48:08PM +0200, Ard Biesheuvel wrote:
> > Update the x86 boot path to avoid the bare metal decompressor when
> > booting via the EFI stub. The bare metal decompressor inherits the
> > loader's 1:1 mapping of DRAM when entering in 64-bit mode, and assumes
> > that all of it is mapped read/write/execute, which will no longer be the
> > case on systems built to comply with recently tightened logo
> > requirements (*).
> >
> > Changes since v7 [10]:
>
> My Zen1 box fails booting with those. It is related to memory encryption
> because if I supply "mem_encrypt=off", it boots.
>
> The failure is (typing it off from the video from the BMC):
>
> /dev/root: Can't open blockdev
> VFS: Cannot open root device "UUID=..."
> Please append a correct "root=" boot option;
> ...
>
> I'll bisect now but it is pretty clear which one is the culprit.
>

So this is the host booting, right? So is the position of the C bit
perhaps getting detect incorrectly?