phantom drives in GRUB on Apple Macbook Pro

[Chris Murphy]

Hi,

First reported on Btrfs list, because I'm pretty sure it's a related factor
https://lore.kernel.org/linux-btrfs/address@hidden/T/#t

Hardware:
Macboo Pro 8,2 (2001)
(1) Samsung SSD drive
(1) internal DVD-ROM drive
(2) USB 2, nothing external connected but built-in keyboard shows up
as USB device
(1) wired ethernet
firmware,

GRUB 2.04-3.fc32.x86_64 (Fedora Rawhide GRUB)

SSD partition layout:
1 FAT32 EFI system partition (unused)
2 APFS (macOS)
3 HFS+ (used as ESP by Fedora)
4 Btrfs, sysroot
5 swap
6 Btrfs, sysroot

That is, partitions 4 and 6 are member devices for the Btrfs used as
system root, using single profile for both metadata and data. The
typical case is partition 4 alone is used for sysroot, but it started
to get full so instead of deleting a bunch of stuff I just added
partition 6 to the Btrfs volume. Following a kernel update is when the
GRUB errors show up. I have no proof yet but I think there's more than
one thing going on, interacting with each other.

Shaky cam video of the boot is here:
https://photos.app.goo.gl/wvJbB6kBEFzNwogo6

a. Pretty sure the h0, hd1, hd2, hd3, hd4 phantom drives have been
present for some time, not new in 2.04
b. The "failure reading sector" error by efidisk.c is something that
only showed up soon after adding sda6 to Btrfs sysroot, and
immediately after installing a new kernel while it was in this two
device volume state.
c. This system has been in this state before (months ago) and
immediately after removing the 2nd btrfs device, the failure errors
went away - although I'm still fairly sure the phantom GRUB hdX
devices were present. Nevertheless I have no proof the two device
Btrfs is related, and isn't just a coincidence.

Photos of "lsefi" output
https://photos.app.goo.gl/pBxLJNdbzz6J9Vo56


-- 
Chris Murphy