On 2/15/26 09:48, Heinrich Schuchardt wrote:
On 2/11/26 16:56, Michal Simek wrote:
From: Shantur Rathore <[email protected]>
Currently U-Boot uses ESP as storage for EFI variables.
Devices with SPI Flash are used for storing environment with this
commit we allow EFI variables to be stored on SPI Flash.
https://github.com/rhboot/efivar
is not updated to support this location that's why you can mimic it by
running:
dd if=/sys/firmware/efi/efivars/VarToFile-b2ac5fc9-92b7-4acd-aeac-11e818c3130c \
of=/tmp/vars skip=4 bs=1
flashcp /tmp/vars /dev/mtdX
where mtdX should match location defined by
CONFIG_EFI_VARIABLE_SF_OFFSET/CONFIG_EFI_VAR_BUF_SIZE.
Signed-off-by: Shantur Rathore <[email protected]>
Signed-off-by: Michal Simek <[email protected]>
Tested-by: Neil Armstrong <[email protected]> # on AML-S905D3-CC
Acked-by: Ilias Apalodimas <[email protected]>
---
Changes in v8:
- Add missing EFI_VARIABLE_SF_STORE dependency to EFI_VARIABLE_SF_DEVICE_INDEX
Changes in v7:
- sed -i 's/efi_var_from/efi_var_from_storage/g'
Changes in v6:
- sed -i 's/efi_var_read/efi_var_from/g'
- sed -i 's/efi_var_write/efi_var_to_storage/g'
Changes in v4:
- Extend Kconfig description
- Extend commit message and describe efivar missing part
- use unify methods for reading/writing variable
Changes in v3:
- Fixed compiler warnings.
Changes in v2:
- Refactored efi_var_file to move common parts out as requested
- Changed ifdefs to use CONFIG_IS_DEFINED
- Fixed typos
lib/efi_loader/Kconfig | 35 +++++++++++++-
lib/efi_loader/Makefile | 1 +
lib/efi_loader/efi_var_sf.c | 92 +++++++++++++++++++++++++++++++++++++
3 files changed, 127 insertions(+), 1 deletion(-)
create mode 100644 lib/efi_loader/efi_var_sf.c
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 579eed658801..0f6f927ddaf1 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -124,6 +124,24 @@ config EFI_VARIABLE_FILE_STORE
Select this option if you want non-volatile UEFI variables to be
stored as file /ubootefi.var on the EFI system partition.
+config EFI_VARIABLE_SF_STORE
+ bool "Store non-volatile UEFI variables in SPI Flash"
+ depends on SPI_FLASH
+ help
+ Select this option if you want non-volatile UEFI variables to be
+ stored in SPI Flash.
+
+ Define CONFIG_EFI_VARIABLE_SF_OFFSET as offset in SPI Flash to use as
+ the storage for variables. CONFIG_EFI_VAR_BUF_SIZE defines the space
+ needed.
+
+ Note that SPI Flash devices have a limited number of program/erase
+ cycles. Frequent updates to UEFI variables may cause excessive wear
+ and can permanently damage the flash device, particularly on SPI NAND
+ or low-end SPI NOR parts without wear leveling. This option should be
+ used with care on such systems, and is not recommended for platforms
+ where UEFI variables are updated frequently.
+
config EFI_MM_COMM_TEE
bool "UEFI variables storage service via the trusted world"
depends on OPTEE
@@ -153,7 +171,7 @@ endchoice
config EFI_RT_VOLATILE_STORE
bool "Allow variable runtime services in volatile storage (e.g RAM)"
- depends on EFI_VARIABLE_FILE_STORE
+ depends on EFI_VARIABLE_FILE_STORE || EFI_VARIABLE_SF_STORE
Hello Michal,
If the backend store is SPI flash, we should not publish the variable
"RTStorageVolatile" at runtime as currently defined.
For the background see this commit for the efivar library:
https://github.com/rhboot/efivar/commit/68daa04654acbe1bbaa17ebfc23c371b39e69c6b
The first three patches look correct to me and I will add them to a merge
request for efi-next.
Do I read it that when I don't allow to select EFI_RT_VOLATILE_STORE you will be
fine with the patch itself?
The usage of efi_var_mem_ins() and efi_var_mem_del() when SetVariable() does not
change anything is not flash-friendly. Michal, do you want to have a look at
this area?
That's known limitation describe in EFI_VARIABLE_SF_STORE Kconfig Note.
Thanks,
Michal
