[PATCH 01/12] riscv: integrate alternatives better into the main architecture

Heiko Stuebner
2022-05-11T19:30:24Z

Right now the alternatives need to be explicitly enabled and
erratas are limited to SiFive ones.

We want to use alternatives not only for patching soc erratas,
but in the future also for handling different behaviour depending
on the existence of future extensions.

So move the core alternatives over to the kernel subdirectory
and move the CONFIG_RISCV_ALTERNATIVE to be a hidden symbol
which we expect relevant erratas and extensions to just select
if needed.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>
---
arch/riscv/Kconfig | 9 +++++++++
arch/riscv/Kconfig.erratas | 13 ++-----------
arch/riscv/Kconfig.socs | 1 -
arch/riscv/Makefile | 2 +-
arch/riscv/errata/Makefile | 1 -
arch/riscv/include/asm/alternative-macros.h | 7 ++++---
arch/riscv/include/asm/alternative.h | 8 ++++++++
arch/riscv/kernel/Makefile | 1 +
arch/riscv/{errata => kernel}/alternative.c | 0
arch/riscv/kernel/smpboot.c | 2 --
arch/riscv/kernel/traps.c | 2 +-
11 files changed, 26 insertions(+), 20 deletions(-)
rename arch/riscv/{errata => kernel}/alternative.c (100%)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index f8a55d94016d..1ec07aa582a3 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -325,6 +325,15 @@ config NODES_SHIFT
Specify the maximum number of NUMA Nodes available on the target
system. Increases memory reserved to accommodate various tables.

+config RISCV_ALTERNATIVE
+ bool
+ depends on !XIP_KERNEL
+ help
+ This Kconfig allows the kernel to automatically patch the
+ errata required by the execution platform at run time. The
+ code patching is performed once in the boot stages. It means
+ that the overhead from this mechanism is just taken once.
+
config RISCV_ISA_C
bool "Emit compressed instructions when building Linux"
default y
diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
index 0aacd7052585..c521c2ae2de2 100644
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -1,18 +1,9 @@
menu "CPU errata selection"

-config RISCV_ERRATA_ALTERNATIVE
- bool "RISC-V alternative scheme"
- depends on !XIP_KERNEL
- default y
- help
- This Kconfig allows the kernel to automatically patch the
- errata required by the execution platform at run time. The
- code patching is performed once in the boot stages. It means
- that the overhead from this mechanism is just taken once.
-
config ERRATA_SIFIVE
bool "SiFive errata"
- depends on RISCV_ERRATA_ALTERNATIVE
+ depends on !XIP_KERNEL
+ select RISCV_ALTERNATIVE
help
All SiFive errata Kconfig depend on this Kconfig. Disabling
this Kconfig will disable all SiFive errata. Please say "Y"
diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
index f6ef358d8a2c..85670dc9fe95 100644
--- a/arch/riscv/Kconfig.socs
+++ b/arch/riscv/Kconfig.socs
@@ -14,7 +14,6 @@ config SOC_SIFIVE
select CLK_SIFIVE
select CLK_SIFIVE_PRCI
select SIFIVE_PLIC
- select RISCV_ERRATA_ALTERNATIVE if !XIP_KERNEL
select ERRATA_SIFIVE if !XIP_KERNEL
help
This enables support for SiFive SoC platform hardware.
diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
index 7d81102cffd4..a7ed47ce9311 100644
--- a/arch/riscv/Makefile
+++ b/arch/riscv/Makefile
@@ -103,7 +103,7 @@ endif

head-y := arch/riscv/kernel/head.o

-core-$(CONFIG_RISCV_ERRATA_ALTERNATIVE) += arch/riscv/errata/
+core-y += arch/riscv/errata/
core-$(CONFIG_KVM) += arch/riscv/kvm/

libs-y += arch/riscv/lib/
diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index b8f8740a3e44..0ca1c5281a2d 100644
--- a/arch/riscv/errata/Makefile
+++ b/arch/riscv/errata/Makefile
@@ -1,2 +1 @@
-obj-y += alternative.o
obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
diff --git a/arch/riscv/include/asm/alternative-macros.h b/arch/riscv/include/asm/alternative-macros.h
index 67406c376389..5dd8d03a13da 100644
--- a/arch/riscv/include/asm/alternative-macros.h
+++ b/arch/riscv/include/asm/alternative-macros.h
@@ -2,7 +2,7 @@
#ifndef __ASM_ALTERNATIVE_MACROS_H
#define __ASM_ALTERNATIVE_MACROS_H

-#ifdef CONFIG_RISCV_ERRATA_ALTERNATIVE
+#ifdef CONFIG_RISCV_ALTERNATIVE

#ifdef __ASSEMBLY__

@@ -76,7 +76,7 @@

#endif /* __ASSEMBLY__ */

-#else /* !CONFIG_RISCV_ERRATA_ALTERNATIVE*/
+#else /* CONFIG_RISCV_ALTERNATIVE */
#ifdef __ASSEMBLY__

.macro __ALTERNATIVE_CFG old_c
@@ -95,7 +95,8 @@
__ALTERNATIVE_CFG(old_c)

#endif /* __ASSEMBLY__ */
-#endif /* CONFIG_RISCV_ERRATA_ALTERNATIVE */
+#endif /* CONFIG_RISCV_ALTERNATIVE */
+
/*
* Usage:
* ALTERNATIVE(old_content, new_content, vendor_id, errata_id, CONFIG_k)
diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
index e625d3cafbed..7b42bcef0ecf 100644
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -12,6 +12,8 @@

#ifndef __ASSEMBLY__

+#ifdef CONFIG_RISCV_ALTERNATIVE
+
#include <linux/init.h>
#include <linux/types.h>
#include <linux/stddef.h>
@@ -35,5 +37,11 @@ struct errata_checkfunc_id {
void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
unsigned long archid, unsigned long impid);

+#else /* CONFIG_RISCV_ALTERNATIVE */
+
+static inline void apply_boot_alternatives(void) { }
+
+#endif /* CONFIG_RISCV_ALTERNATIVE */
+
#endif
#endif
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 87adbe47bc15..0f8348ac30f1 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -18,6 +18,7 @@ extra-y += head.o
extra-y += vmlinux.lds

obj-y += soc.o
+obj-$(CONFIG_RISCV_ALTERNATIVE) += alternative.o
obj-y += cpu.o
obj-y += cpufeature.o
obj-y += entry.o
diff --git a/arch/riscv/errata/alternative.c b/arch/riscv/kernel/alternative.c
similarity index 100%
rename from arch/riscv/errata/alternative.c
rename to arch/riscv/kernel/alternative.c
diff --git a/arch/riscv/kernel/smpboot.c b/arch/riscv/kernel/smpboot.c
index 622f226454d5..a6d13dca1403 100644
--- a/arch/riscv/kernel/smpboot.c
+++ b/arch/riscv/kernel/smpboot.c
@@ -41,9 +41,7 @@ static DECLARE_COMPLETION(cpu_running);
void __init smp_prepare_boot_cpu(void)
{
init_cpu_topology();
-#ifdef CONFIG_RISCV_ERRATA_ALTERNATIVE
apply_boot_alternatives();
-#endif
}

void __init smp_prepare_cpus(unsigned int max_cpus)
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index fe92e119e6a3..efa693b325a1 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -86,7 +86,7 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
}
}

-#if defined (CONFIG_XIP_KERNEL) && defined (CONFIG_RISCV_ERRATA_ALTERNATIVE)
+#if defined (CONFIG_XIP_KERNEL) && defined (CONFIG_RISCV_ALTERNATIVE)
#define __trap_section __section(".xip.traps")
#else
#define __trap_section
--
2.35.1