[PATCH v3 0/4] efi: Fix handling of multiple efi_fake_mem= entries

From: Dan Williams
Date: Wed Jan 01 2020 - 23:29:39 EST

Changes since v2 [1]:
- Move the efi_memmap_free() until efi_memmap_install() is committed to
installing the new map. (Dave).

- Handle the case of a memblock allocated memmap being freed after the slab
allocator is up. Just use memblock_free_late() for that case rather
than warn. (Prompted by Dave's feedback on how many successful
efi_memmap_free() calls occur during a boot).

- Not changed was anything additional related to Dave's concern about
efi_fake_mem= being applied to overlapping entries. I tested
"efi_fake_mem=4G@9G:0x40000,4G@12G:0x40000" which triggers the second
entry to overwrite the first as well as another entry. The result is
reasonable and functional for what is otherwise garbage input:

efi: mem53: [Conventional Memory| | |SP| | | | | | |WB|WT|WC|UC] range=[0x240000000-0x2ffffffff] (3072MB)
efi: mem54: [Conventional Memory| | |SP| | | | | | |WB|WT|WC|UC] range=[0x300000000-0x33fffffff] (1024MB)
efi: mem55: [Conventional Memory| | |SP| | | | | | |WB|WT|WC|UC] range=[0x340000000-0x3ffffffff] (3072MB)
efi: mem56: [Conventional Memory| | | | | | | | | |WB|WT|WC|UC] range=[0x400000000-0x43fffffff] (1024MB)

# cat /proc/iomem | grep Sof
240000000-3ffffffff : Soft Reserved

[1]: http://lore.kernel.org/r/157782985777.367056.14741265874314204783.stgit@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx


While testing an upcoming patchset to enhance the "soft reservation"
implementation it started crashing when rebased on v5.5-rc3. This
uncovered a few bugs in the efi_fake_mem= handling and
efi_memmap_alloc() leaks.


Copied from patch4:

Dave noticed that when specifying multiple efi_fake_mem= entries only
the last entry was successfully being reflected in the efi memory map.
This is due to the fact that the efi_memmap_insert() is being called
multiple times, but on successive invocations the insertion should be
applied to the last new memmap rather than the original map at
efi_fake_memmap() entry.

Rework efi_fake_memmap() to install the new memory map after each
efi_fake_mem= entry is parsed.

This also fixes an issue in efi_fake_memmap() that caused it to litter
emtpy entries into the end of the efi memory map. The empty entry causes
efi_memmap_insert() to attempt more memmap splits / copies than
efi_memmap_split_count() accounted for when sizing the new map.

BUG: unable to handle page fault for address: ffffffffff281000
RIP: 0010:efi_memmap_insert+0x11d/0x191
Call Trace:
? bgrt_init+0xbe/0xbe
? efi_arch_mem_reserve+0x1cb/0x228
? acpi_parse_bgrt+0xa/0xd
? acpi_table_parse+0x86/0xb8
? acpi_boot_init+0x494/0x4e3
? acpi_parse_x2apic+0x87/0x87
? setup_acpi_sci+0xa2/0xa2
? setup_arch+0x8db/0x9e1
? start_kernel+0x6a/0x547
? secondary_startup_64+0xb6/0xc0

Commit af1648984828 "x86/efi: Update e820 with reserved EFI boot
services data to fix kexec breakage" is listed in Fixes: since it
introduces more occurrences where efi_memmap_insert() is invoked after
an efi_fake_mem= configuration has been parsed. Previously the side
effects of vestigial empty entries were benign, but with commit
af1648984828 that follow-on efi_memmap_insert() invocation triggers the
above crash signature.


Dan Williams (4):
efi: Add a flags parameter to efi_memory_map
efi: Add tracking for dynamically allocated memmaps
efi: Fix efi_memmap_alloc() leaks
efi: Fix handling of multiple efi_fake_mem= entries

arch/x86/platform/efi/efi.c | 2 +
arch/x86/platform/efi/quirks.c | 11 ++++---
drivers/firmware/efi/fake_mem.c | 37 +++++++++++++------------
drivers/firmware/efi/memmap.c | 58 ++++++++++++++++++++++++++++++---------
include/linux/efi.h | 13 +++++++--
5 files changed, 81 insertions(+), 40 deletions(-)