[PATCH v2] RISC-V: Add CONFIG_{NON,}PORTABLE

From: Palmer Dabbelt
Date: Wed Apr 13 2022 - 21:41:05 EST


From: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

The RISC-V port has collected a handful of options that are
fundamentally non-portable. To prevent users from shooting themselves
in the foot, hide them all behind a config entry that explicitly calls
out that non-portable binaries may be produced.

Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>

---

Changes since v1:

* Fix a bunch of spelling mistakes.
* Move NONPORTABLE under the "Platform type" sub-heading.
* Fix the rv32i dependency.
---
arch/riscv/Kconfig | 28 ++++++++++++++++++++++++++--
1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 5adcbd9b5e88..3d8eb44eb889 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -213,6 +213,21 @@ source "arch/riscv/Kconfig.erratas"

menu "Platform type"

+config NONPORTABLE
+ bool "Allow configurations that result in non-portable kernels"
+ help
+ RISC-V kernel binaries are compatible between all known systems
+ whenever possible, but there are some use cases that can only be
+ satisfied by configurations that result in kernel binaries that are
+ not portable between systems.
+
+ Selecting N does not guarantee kernels will be portable to all knows
+ systems. Selecting any of the options guarded by NONPORTABLE will
+ result in kernel binaries that are unlikely to be portable between
+ systems.
+
+ If unsure, say N.
+
choice
prompt "Base ISA"
default ARCH_RV64I
@@ -222,6 +237,7 @@ choice

config ARCH_RV32I
bool "RV32I"
+ depends on NONPORTABLE
select 32BIT
select GENERIC_LIB_ASHLDI3
select GENERIC_LIB_ASHRDI3
@@ -485,6 +501,7 @@ config STACKPROTECTOR_PER_TASK

config PHYS_RAM_BASE_FIXED
bool "Explicitly specified physical RAM address"
+ depends on NONPORTABLE
default n

config PHYS_RAM_BASE
@@ -498,7 +515,7 @@ config PHYS_RAM_BASE

config XIP_KERNEL
bool "Kernel Execute-In-Place from ROM"
- depends on MMU && SPARSEMEM
+ depends on MMU && SPARSEMEM && NONPORTABLE
# This prevents XIP from being enabled by all{yes,mod}config, which
# fail to build since XIP doesn't support large kernels.
depends on !COMPILE_TEST
@@ -538,9 +555,16 @@ endmenu

config BUILTIN_DTB
bool
- depends on OF
+ depends on OF && NONPORTABLE
default y if XIP_KERNEL

+config PORTABLE
+ bool
+ default !NONPORTABLE
+ select EFI
+ select OF
+ select MMU
+
menu "Power management options"

source "kernel/power/Kconfig"
--
2.34.1