Issue #617 has been updated by gaspar ilom.
Maximilian Brune wrote in #note-3:
> What does your `build/fmap.fmd` file look like?
```
cat ./build/x86/coreboot-25.09/EOL_w541-maximized/fmap.fmd
# layout for firmware residing at top of 4GB address space
# +-------------+ <-- 4GB - ROM_SIZE / start of flash
# | unspecified |
# +-------------+ <-- 4GB - BIOS_SIZE
# | FMAP |
# +-------------+ <-- 4GB - BIOS_SIZE + FMAP_SIZE
# | CBFS |
# +-------------+ <-- 4GB / end of flash
FLASH 0x00c00000 {
BIOS@131072 12451840 {
RW_MRC_CACHE@0 0x10000
FMAP@65536 0x200
COREBOOT(CBFS)@66048 12385792
}
}
```
----------------------------------------
Bug #617: Missing safeguard: CBFS_SIZE greater than BIOS region in the IFD
https://ticket.coreboot.org/issues/617#change-2183
* Author: gaspar ilom
* Status: New
* Priority: Normal
* Target version: none
* Start date: 2025-11-14
* Affected versions: main
* Affected hardware: haswell
----------------------------------------
There are no effective safeguards to enforce that the `CONFIG_CBFS_SIZE` does
not exceed the bios region as declared in the IFD.
### Impact
- Downstream under Heads with a maximized bios region for the Haswell boards
(T440p and W541) we could verify that this bug leads to an overflow when
training the memory cache that makes it not work. This happens both with MRC
blob and NRI and causes very slow boot times (20s) and S3 suspend/resume does
not work.
- Effects on other boards have not been observed but are possible.
### Expected behavior
Coreboot should not build successfully if the `CBFS_SIZE` exceeds the bios
region in the IFD and error out reporting the problem that caused this.
## Analysis
Full details are under the PR in Heads and in particular this comment by
@tlaurion https://github.com/linuxboot/heads/pull/2025/#issuecomment-3524672338
Ifttool reports a bios region of 0xBDEFFF (BDEFFF).
However, the coreboot config contained:
```
CONFIG_CBFS_SIZE=0xBE4FFF
```
```
./build/x86/coreboot-25.09/util/ifdtool/ifdtool --platform ifd2 --layout
w541_layout blobs/w541/ifd.bin && cat w541_layout
File blobs/w541/ifd.bin is 4096 bytes
Wrote layout to w541_layout
00000000:00000fff fd
00021000:00bfffff bios
00003000:00020fff me
00001000:00002fff gbe
```
After fixing the `CONFIG_CBFS_SIZE` the issues were fixed and fast boot with
trained memory cache and S3 suspen/resume work again with NRI:
https://github.com/linuxboot/heads/pull/2025/commits/9b8b9cacdcea4f67c95dcec10b3153fc8c016940
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