On 6/25/25 16:21, Aleksa Paunovic via B4 Relay wrote:
From: Djordje Todorovic <djordje.todorovic@xxxxxxxxxxxxx>
Add ERRATA_MIPS and ERRATA_MIPS_P8700_PAUSE_OPCODE configs.
Handle errata for the MIPS PAUSE instruction.
Signed-off-by: Djordje Todorovic <djordje.todorovic@xxxxxxxxxxxxx>
Signed-off-by: Aleksandar Rikalo <arikalo@xxxxxxxxx>
Signed-off-by: Raj Vishwanathan4 <rvishwanathan@xxxxxxxx>
Signed-off-by: Aleksa Paunovic <aleksa.paunovic@xxxxxxxxxxxxx>
---
arch/riscv/Kconfig.errata | 23 +++++++++++
arch/riscv/errata/Makefile | 1 +
arch/riscv/errata/mips/Makefile | 5 +++
arch/riscv/errata/mips/errata.c | 67 +++++++++++++++++++++++++++++++++
arch/riscv/include/asm/alternative.h | 3 ++
arch/riscv/include/asm/cmpxchg.h | 3 +-
arch/riscv/include/asm/errata_list.h | 17 ++++++++-
arch/riscv/include/asm/vdso/processor.h | 4 +-
arch/riscv/include/asm/vendorid_list.h | 1 +
arch/riscv/kernel/alternative.c | 5 +++
arch/riscv/kernel/entry.S | 2 +
arch/riscv/mm/init.c | 1 +
12 files changed, 129 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/Kconfig.errata b/arch/riscv/Kconfig.errata
index e318119d570de0acc0850a2e1a2505ecb71bea08..aca9b0cfcfecf91d4d1910f294ee109ed15f2d6c 100644
--- a/arch/riscv/Kconfig.errata
+++ b/arch/riscv/Kconfig.errata
@@ -21,6 +21,29 @@ config ERRATA_ANDES_CMO
If you don't know what to do here, say "Y".
+config ERRATA_MIPS
+ bool "MIPS errata"
+ depends on RISCV_ALTERNATIVE
+ help
+ All MIPS errata Kconfig depend on this Kconfig. Disabling
+ this Kconfig will disable all MIPS errata. Please say "Y"
+ here if your platform uses MIPS CPU cores.
+
+ Otherwise, please say "N" here to avoid unnecessary overhead.
+
+config ERRATA_MIPS_P8700_PAUSE_OPCODE
+ bool "Fix the PAUSE Opcode for MIPS P8700"
+ depends on ERRATA_MIPS && 64BIT
+ default n
+ help
+ The RISCV MIPS P8700 uses a different opcode for PAUSE.
+ It is a 'hint' encoding of the SLLI instruction,
+ with rd=0, rs1=0 and imm=5. It will behave as a NOP
+ instruction if no additional behavior beyond that of
+ SLLI is implemented.
+
+ If you are not using the P8700 processor, say n.
+
config ERRATA_SIFIVE
bool "SiFive errata"
depends on RISCV_ALTERNATIVE
diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index bc6c77ba837d2da4c98dabab18083d27f46629c7..02a7a3335b1d557933e04cd6d0cf7bf4260b8c40 100644
--- a/arch/riscv/errata/Makefile
+++ b/arch/riscv/errata/Makefile
@@ -13,5 +13,6 @@ endif
endif
obj-$(CONFIG_ERRATA_ANDES) += andes/
+obj-$(CONFIG_ERRATA_MIPS) += mips/
obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
obj-$(CONFIG_ERRATA_THEAD) += thead/
diff --git a/arch/riscv/errata/mips/Makefile b/arch/riscv/errata/mips/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..6278c389b801ee6e54e808c80e6e236c026329c7
--- /dev/null
+++ b/arch/riscv/errata/mips/Makefile
@@ -0,0 +1,5 @@
+ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
+CFLAGS_errata.o := -mcmodel=medany
+endif
+
+obj-y += errata.o
diff --git a/arch/riscv/errata/mips/errata.c b/arch/riscv/errata/mips/errata.c
new file mode 100644
index 0000000000000000000000000000000000000000..e984a8152208c34690f89d8101571b097485c360
--- /dev/null
+++ b/arch/riscv/errata/mips/errata.c
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 MIPS.
+ */
+
+#include <linux/memory.h>
+#include <linux/module.h>
+#include <asm/text-patching.h>
+#include <asm/alternative.h>
+#include <asm/errata_list.h>
+#include <asm/vendorid_list.h>
+#include <asm/vendor_extensions.h>
+#include <asm/vendor_extensions/mips.h>
+
+static inline bool errata_probe_pause(void)
+{
+ if (!IS_ENABLED(CONFIG_ERRATA_MIPS_P8700_PAUSE_OPCODE))
+ return false;
+
+ if (!riscv_isa_vendor_extension_available(MIPS_VENDOR_ID, XMIPSEXECTL))
+ return false;
+
+ return true;
+}
+
+static u32 mips_errata_probe(void)
+{
+ u32 cpu_req_errata = 0;
+
+ if (errata_probe_pause())
+ cpu_req_errata |= BIT(ERRATA_MIPS_P8700_PAUSE_OPCODE);
+
+ return cpu_req_errata;
+}
+
+void mips_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+ unsigned long archid, unsigned long impid,
+ unsigned int stage)
+{
+ struct alt_entry *alt;
+ u32 cpu_req_errata = mips_errata_probe();
+ u32 tmp;
+
+ BUILD_BUG_ON(ERRATA_MIPS_NUMBER >= RISCV_VENDOR_EXT_ALTERNATIVES_BASE);
+
+ if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
+ return;
+
+ for (alt = begin; alt < end; alt++) {
+ if (alt->vendor_id != MIPS_VENDOR_ID)
+ continue;
+
+ if (alt->patch_id >= ERRATA_MIPS_NUMBER) {
+ WARN(1, "MIPS errata id:%d not in kernel errata list\n",
+ alt->patch_id);
+ continue;
+ }
+
+ tmp = (1U << alt->patch_id);
+ if (cpu_req_errata && tmp) {
+ mutex_lock(&text_mutex);
+ patch_text_nosync(ALT_OLD_PTR(alt), ALT_ALT_PTR(alt),
+ alt->alt_len);
+ mutex_unlock(&text_mutex);
+ }
+ }
+}
diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
index 3c2b59b25017929df92b4e6741ac1a9308bfec54..bc3ada8190a9e7dc7d904aeb3174c78329e4d8d7 100644
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -48,6 +48,9 @@ struct alt_entry {
void andes_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
unsigned long archid, unsigned long impid,
unsigned int stage);
+void mips_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
+ unsigned long archid, unsigned long impid,
+ unsigned int stage);
void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
unsigned long archid, unsigned long impid,
unsigned int stage);
diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
index 0b749e7102162477432f7cf9a34768fbdf2e8cc7..80bd52363c68690f33bfd54e0cc40399cd60b57b 100644
--- a/arch/riscv/include/asm/cmpxchg.h
+++ b/arch/riscv/include/asm/cmpxchg.h
@@ -14,6 +14,7 @@
#include <asm/insn-def.h>
#include <asm/cpufeature-macros.h>
#include <asm/processor.h>
+#include <asm/errata_list.h>
#define __arch_xchg_masked(sc_sfx, swap_sfx, prepend, sc_append, \
swap_append, r, p, n) \
@@ -438,7 +439,7 @@ static __always_inline void __cmpwait(volatile void *ptr,
return;
no_zawrs:
- asm volatile(RISCV_PAUSE : : : "memory");
+ ALT_RISCV_PAUSE();
}
#define __cmpwait_relaxed(ptr, val) \
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index 6e426ed7919a4acd997b60b723c0d5cfddb4cff6..618dee38d8d1347711fd46a459bfc8d2cb7bf42b 100644
--- a/arch/riscv/include/asm/errata_list.h
+++ b/arch/riscv/include/asm/errata_list.h
@@ -5,7 +5,6 @@
#ifndef ASM_ERRATA_LIST_H
#define ASM_ERRATA_LIST_H
-#include <asm/alternative.h>
#include <asm/csr.h>
#include <asm/insn-def.h>
#include <asm/hwcap.h>
@@ -29,6 +28,11 @@
#define ERRATA_THEAD_NUMBER 3
#endif
+#ifdef CONFIG_ERRATA_MIPS
+#define ERRATA_MIPS_P8700_PAUSE_OPCODE 0
+#define ERRATA_MIPS_NUMBER 1
+#endif
+
#ifdef __ASSEMBLY__
#define ALT_INSN_FAULT(x) \
@@ -59,6 +63,17 @@ asm(ALTERNATIVE("sfence.vma %0, %1", "sfence.vma", SIFIVE_VENDOR_ID, \
ERRATA_SIFIVE_CIP_1200, CONFIG_ERRATA_SIFIVE_CIP_1200) \
: : "r" (addr), "r" (asid) : "memory")
+#define ALT_RISCV_PAUSE() \
+asm(ALTERNATIVE( \
+ RISCV_PAUSE, /* Original RISC‑V pause insn */ \
+ ".4byte 0x00501013", /* Replacement for MIPS P8700 */ \
Here you should use MIPS_PAUSE
+ MIPS_VENDOR_ID, /* Vendor ID to match */ \
+ ERRATA_MIPS_P8700_PAUSE_OPCODE, /* patch_id */ \
+ CONFIG_ERRATA_MIPS_P8700_PAUSE_OPCODE) \
+ : /* no outputs */ \
+ : /* no inputs */ \
+ : "memory")
+
/*
* _val is marked as "will be overwritten", so need to set it to 0
* in the default case.
diff --git a/arch/riscv/include/asm/vdso/processor.h b/arch/riscv/include/asm/vdso/processor.h
index 8f383f05a290f123d941226b5dd975381d7d8536..8f749552ecfe6220bbc35f1c4677c6de8f7abdec 100644
--- a/arch/riscv/include/asm/vdso/processor.h
+++ b/arch/riscv/include/asm/vdso/processor.h
@@ -5,6 +5,8 @@
#ifndef __ASSEMBLY__
#include <asm/barrier.h>
+
New line ^
+#include <asm/errata_list.h>
#include <asm/insn-def.h>
static inline void cpu_relax(void)
@@ -19,7 +21,7 @@ static inline void cpu_relax(void)
* Reduce instruction retirement.
* This assumes the PC changes.
*/
- __asm__ __volatile__ (RISCV_PAUSE);
+ ALT_RISCV_PAUSE();
barrier();
}
diff --git a/arch/riscv/include/asm/vendorid_list.h b/arch/riscv/include/asm/vendorid_list.h
index a5150cdf34d87f01baf6d3ef843bc2d6d8d54095..3b09874d7a6dfb8f8aa45b0be41c20711d539e78 100644
--- a/arch/riscv/include/asm/vendorid_list.h
+++ b/arch/riscv/include/asm/vendorid_list.h
@@ -9,5 +9,6 @@
#define MICROCHIP_VENDOR_ID 0x029
#define SIFIVE_VENDOR_ID 0x489
#define THEAD_VENDOR_ID 0x5b7
+#define MIPS_VENDOR_ID 0x722
#endif
diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
index 7eb3cb1215c62130c63a72fc650cddff6bae62af..7642704c7f1841f67fc23738063f22b4ecf58194 100644
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -47,6 +47,11 @@ static void riscv_fill_cpu_mfr_info(struct cpu_manufacturer_info_t *cpu_mfr_info
cpu_mfr_info->patch_func = andes_errata_patch_func;
break;
#endif
+#ifdef CONFIG_ERRATA_MIPS
+ case MIPS_VENDOR_ID:
+ cpu_mfr_info->patch_func = mips_errata_patch_func;
+ break;
+#endif
#ifdef CONFIG_ERRATA_SIFIVE
case SIFIVE_VENDOR_ID:
cpu_mfr_info->patch_func = sifive_errata_patch_func;
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 75656afa2d6be8ca5f2c4711455567c7f8fc0b97..b18373ed23d65df0dc828246269e9039bb0b0c6b 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -15,6 +15,8 @@
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
#include <asm/errata_list.h>
+#include <asm/alternative.h>
+
#include <linux/sizes.h>
.section .irqentry.text, "ax"
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 8d0374d7ce8ed72320f58e4cea212d0e2bce8fd4..7ee95ebadc258a3a46e59698cd143266f6797a0c 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -33,6 +33,7 @@
#include <asm/soc.h>
#include <asm/sparsemem.h>
#include <asm/tlbflush.h>
+#include <asm/alternative.h>
#include "../kernel/head.h"
Why do you include alternative.h in both files above? That does not seem
needed.
Other than that:
Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
Thanks,
Alex
