On 17. 7. 25. 13:43, Alexandre Ghiti wrote:
> 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.
Hi Alexandre,
Thank you for reviewing the series.
We ran into similar header problems with these as we did with mips.h. Moving alternative.h
from errata_list.h to init.c seemed like the simplest solution. Including into
entry.S does seem unnecessary, though.
I addressed the rest of your comments in v5.
Best regards,
Aleksa
>
> Other than that:
>
> Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>
>
> Thanks,
>
> Alex
