Re: [PATCH 12/12] riscv: add memory-type errata for T-Head

Guo Ren
2022-05-13T13:38:49Z

Reviewed-by: Guo Ren <guoren@kernel.org>

On Thu, May 12, 2022 at 3:33 AM Heiko Stuebner <heiko@sntech.de> wrote:
>
> Some current cpus based on T-Head cores implement memory-types
> way different than described in the svpbmt spec even going
> so far as using PTE bits marked as reserved.
>
> Add the T-Head vendor-id and necessary errata code to
> replace the affected instructions.
>
> Signed-off-by: Heiko Stuebner <heiko@sntech.de>
> Tested-by: Samuel Holland <samuel@sholland.org>
> ---
> arch/riscv/Kconfig | 6 ++
> arch/riscv/Kconfig.erratas | 21 +++++++
> arch/riscv/errata/Makefile | 1 +
> arch/riscv/errata/sifive/errata.c | 7 ++-
> arch/riscv/errata/thead/Makefile | 11 ++++
> arch/riscv/errata/thead/errata.c | 82 ++++++++++++++++++++++++++
> arch/riscv/include/asm/alternative.h | 6 ++
> arch/riscv/include/asm/errata_list.h | 50 +++++++++++++++-
> arch/riscv/include/asm/pgtable-64.h | 18 +++++-
> arch/riscv/include/asm/pgtable.h | 18 +++++-
> arch/riscv/include/asm/vendorid_list.h | 1 +
> arch/riscv/kernel/Makefile | 14 +++++
> arch/riscv/kernel/alternative.c | 26 ++++++++
> arch/riscv/kernel/cpufeature.c | 7 ++-
> arch/riscv/mm/init.c | 1 +
> 15 files changed, 260 insertions(+), 9 deletions(-)
> create mode 100644 arch/riscv/errata/thead/Makefile
> create mode 100644 arch/riscv/errata/thead/errata.c
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 90317a3d40a8..65285b980134 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -334,6 +334,12 @@ config RISCV_ALTERNATIVE
> code patching is performed once in the boot stages. It means
> that the overhead from this mechanism is just taken once.
>
> +config RISCV_ALTERNATIVE_EARLY
> + bool
> + depends on RISCV_ALTERNATIVE
> + help
> + Allows early patching of the kernel for special errata
> +
> 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 c521c2ae2de2..ebfcd5cc6eaf 100644
> --- a/arch/riscv/Kconfig.erratas
> +++ b/arch/riscv/Kconfig.erratas
> @@ -33,4 +33,25 @@ config ERRATA_SIFIVE_CIP_1200
>
> If you don't know what to do here, say "Y".
>
> +config ERRATA_THEAD
> + bool "T-HEAD errata"
> + select RISCV_ALTERNATIVE
> + help
> + All T-HEAD errata Kconfig depend on this Kconfig. Disabling
> + this Kconfig will disable all T-HEAD errata. Please say "Y"
> + here if your platform uses T-HEAD CPU cores.
> +
> + Otherwise, please say "N" here to avoid unnecessary overhead.
> +
> +config ERRATA_THEAD_PBMT
> + bool "Apply T-Head memory type errata"
> + depends on ERRATA_THEAD && 64BIT
> + select RISCV_ALTERNATIVE_EARLY
> + default y
> + help
> + This will apply the memory type errata to handle the non-standard
> + memory type bits in page-table-entries on T-Head SoCs.
> +
> + If you don't know what to do here, say "Y".
> +
> endmenu
> diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
> index 0ca1c5281a2d..a1055965fbee 100644
> --- a/arch/riscv/errata/Makefile
> +++ b/arch/riscv/errata/Makefile
> @@ -1 +1,2 @@
> obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
> +obj-$(CONFIG_ERRATA_THEAD) += thead/
> diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
> index 3e39587a49dc..672f02b21ce0 100644
> --- a/arch/riscv/errata/sifive/errata.c
> +++ b/arch/riscv/errata/sifive/errata.c
> @@ -88,10 +88,15 @@ void __init_or_module sifive_errata_patch_func(struct alt_entry *begin,
> unsigned int stage)
> {
> struct alt_entry *alt;
> - u32 cpu_req_errata = sifive_errata_probe(archid, impid);
> + u32 cpu_req_errata;
> u32 cpu_apply_errata = 0;
> u32 tmp;
>
> + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> + return;
> +
> + cpu_req_errata = sifive_errata_probe(archid, impid);
> +
> for (alt = begin; alt < end; alt++) {
> if (alt->vendor_id != SIFIVE_VENDOR_ID)
> continue;
> diff --git a/arch/riscv/errata/thead/Makefile b/arch/riscv/errata/thead/Makefile
> new file mode 100644
> index 000000000000..137e700d9d3f
> --- /dev/null
> +++ b/arch/riscv/errata/thead/Makefile
> @@ -0,0 +1,11 @@
> +ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
> +CFLAGS_errata.o := -mcmodel=medany
> +ifdef CONFIG_FTRACE
> +CFLAGS_REMOVE_errata.o = $(CC_FLAGS_FTRACE)
> +endif
> +ifdef CONFIG_KASAN
> +KASAN_SANITIZE_errata.o := n
> +endif
> +endif
> +
> +obj-y += errata.o
> diff --git a/arch/riscv/errata/thead/errata.c b/arch/riscv/errata/thead/errata.c
> new file mode 100644
> index 000000000000..e5d75270b99c
> --- /dev/null
> +++ b/arch/riscv/errata/thead/errata.c
> @@ -0,0 +1,82 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2021 Heiko Stuebner <heiko@sntech.de>
> + */
> +
> +#include <linux/bug.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/string.h>
> +#include <linux/uaccess.h>
> +#include <asm/alternative.h>
> +#include <asm/cacheflush.h>
> +#include <asm/errata_list.h>
> +#include <asm/patch.h>
> +#include <asm/vendorid_list.h>
> +
> +struct errata_info {
> + char name[ERRATA_STRING_LENGTH_MAX];
> + bool (*check_func)(unsigned long arch_id, unsigned long impid);
> + unsigned int stage;
> +};
> +
> +static bool errata_mt_check_func(unsigned long arch_id, unsigned long impid)
> +{
> + if (arch_id != 0 || impid != 0)
> + return false;
> + return true;
> +}
> +
> +static const struct errata_info errata_list[ERRATA_THEAD_NUMBER] = {
> + {
> + .name = "memory-types",
> + .stage = RISCV_ALTERNATIVES_EARLY_BOOT,
> + .check_func = errata_mt_check_func
> + },
> +};
> +
> +static u32 thead_errata_probe(unsigned int stage, unsigned long archid, unsigned long impid)
> +{
> + const struct errata_info *info;
> + u32 cpu_req_errata = 0;
> + int idx;
> +
> + for (idx = 0; idx < ERRATA_THEAD_NUMBER; idx++) {
> + info = &errata_list[idx];
> +
> + if ((stage == RISCV_ALTERNATIVES_MODULE ||
> + info->stage == stage) && info->check_func(archid, impid))
> + cpu_req_errata |= (1U << idx);
> + }
> +
> + return cpu_req_errata;
> +}
> +
> +void __init_or_module thead_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 = thead_errata_probe(stage, archid, impid);
> + u32 tmp;
> +
> + for (alt = begin; alt < end; alt++) {
> + if (alt->vendor_id != THEAD_VENDOR_ID)
> + continue;
> + if (alt->errata_id >= ERRATA_THEAD_NUMBER)
> + continue;
> +
> + tmp = (1U << alt->errata_id);
> + if (cpu_req_errata & tmp) {
> + /* On vm-alternatives, the mmu isn't running yet */
> + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> + memcpy((void *)__pa_symbol(alt->old_ptr),
> + (void *)__pa_symbol(alt->alt_ptr), alt->alt_len);
> + else
> + patch_text_nosync(alt->old_ptr, alt->alt_ptr, alt->alt_len);
> + }
> + }
> +
> + if (stage == RISCV_ALTERNATIVES_EARLY_BOOT)
> + local_flush_icache_all();
> +}
> diff --git a/arch/riscv/include/asm/alternative.h b/arch/riscv/include/asm/alternative.h
> index 64936356c37c..6511dd73e812 100644
> --- a/arch/riscv/include/asm/alternative.h
> +++ b/arch/riscv/include/asm/alternative.h
> @@ -21,8 +21,10 @@
>
> #define RISCV_ALTERNATIVES_BOOT 0 /* alternatives applied during regular boot */
> #define RISCV_ALTERNATIVES_MODULE 1 /* alternatives applied during module-init */
> +#define RISCV_ALTERNATIVES_EARLY_BOOT 2 /* alternatives applied before mmu start */
>
> void __init apply_boot_alternatives(void);
> +void __init apply_early_boot_alternatives(void);
> void apply_module_alternatives(void *start, size_t length);
>
> struct alt_entry {
> @@ -41,6 +43,9 @@ struct errata_checkfunc_id {
> void sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> unsigned long archid, unsigned long impid,
> unsigned int stage);
> +void thead_errata_patch_func(struct alt_entry *begin, struct alt_entry *end,
> + unsigned long archid, unsigned long impid,
> + unsigned int stage);
>
> void riscv_cpufeature_patch_func(struct alt_entry *begin, struct alt_entry *end,
> unsigned int stage);
> @@ -48,6 +53,7 @@ void riscv_cpufeature_patch_func(struct alt_entry *begin, struct alt_entry *end,
> #else /* CONFIG_RISCV_ALTERNATIVE */
>
> static inline void apply_boot_alternatives(void) { }
> +static inline void apply_early_boot_alternatives(void) { }
> static inline void apply_module_alternatives(void *start, size_t length) { }
>
> #endif /* CONFIG_RISCV_ALTERNATIVE */
> diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
> index dbfcd9b72bd8..9e2888dbb5b1 100644
> --- a/arch/riscv/include/asm/errata_list.h
> +++ b/arch/riscv/include/asm/errata_list.h
> @@ -14,6 +14,11 @@
> #define ERRATA_SIFIVE_NUMBER 2
> #endif
>
> +#ifdef CONFIG_ERRATA_THEAD
> +#define ERRATA_THEAD_PBMT 0
> +#define ERRATA_THEAD_NUMBER 1
> +#endif
> +
> #define CPUFEATURE_SVPBMT 0
> #define CPUFEATURE_NUMBER 1
>
> @@ -42,12 +47,51 @@ asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID, \
> * in the default case.
> */
> #define ALT_SVPBMT_SHIFT 61
> +#define ALT_THEAD_PBMT_SHIFT 59
> #define ALT_SVPBMT(_val, prot) \
> -asm(ALTERNATIVE("li %0, 0\t\nnop", "li %0, %1\t\nslli %0,%0,%2", 0, \
> - CPUFEATURE_SVPBMT, CONFIG_RISCV_ISA_SVPBMT) \
> +asm(ALTERNATIVE_2("li %0, 0\t\nnop", \
> + "li %0, %1\t\nslli %0,%0,%3", 0, \
> + CPUFEATURE_SVPBMT, CONFIG_RISCV_ISA_SVPBMT, \
> + "li %0, %2\t\nslli %0,%0,%4", THEAD_VENDOR_ID, \
> + ERRATA_THEAD_PBMT, CONFIG_ERRATA_THEAD_PBMT) \
> : "=r"(_val) \
> : "I"(prot##_SVPBMT >> ALT_SVPBMT_SHIFT), \
> - "I"(ALT_SVPBMT_SHIFT))
> + "I"(prot##_THEAD >> ALT_THEAD_PBMT_SHIFT), \
> + "I"(ALT_SVPBMT_SHIFT), \
> + "I"(ALT_THEAD_PBMT_SHIFT))
> +
> +#ifdef CONFIG_ERRATA_THEAD_PBMT
> +/*
> + * IO/NOCACHE memory types are handled together with svpbmt,
> + * so on T-Head chips, check if no other memory type is set,
> + * and set the non-0 PMA type if applicable.
> + */
> +#define ALT_THEAD_PMA(_val) \
> +asm volatile(ALTERNATIVE( \
> + "nop\n\t" \
> + "nop\n\t" \
> + "nop\n\t" \
> + "nop\n\t" \
> + "nop\n\t" \
> + "nop\n\t" \
> + "nop", \
> + "li t3, %2\n\t" \
> + "slli t3, t3, %4\n\t" \
> + "and t3, %0, t3\n\t" \
> + "bne t3, zero, 2f\n\t" \
> + "li t3, %3\n\t" \
> + "slli t3, t3, %4\n\t" \
> + "or %0, %0, t3\n\t" \
> + "2:", THEAD_VENDOR_ID, \
> + ERRATA_THEAD_PBMT, CONFIG_ERRATA_THEAD_PBMT) \
> + : "+r"(_val) \
> + : "0"(_val), \
> + "I"(_PAGE_MTMASK_THEAD >> ALT_THEAD_PBMT_SHIFT), \
> + "I"(_PAGE_PMA_THEAD >> ALT_THEAD_PBMT_SHIFT), \
> + "I"(ALT_THEAD_PBMT_SHIFT))
> +#else
> +#define ALT_THEAD_PMA(_val)
> +#endif
>
> #endif /* __ASSEMBLY__ */
>
> diff --git a/arch/riscv/include/asm/pgtable-64.h b/arch/riscv/include/asm/pgtable-64.h
> index 2354501f0203..e4ff3e0ab887 100644
> --- a/arch/riscv/include/asm/pgtable-64.h
> +++ b/arch/riscv/include/asm/pgtable-64.h
> @@ -86,6 +86,18 @@ typedef struct {
> #define _PAGE_IO_SVPBMT (1UL << 62)
> #define _PAGE_MTMASK_SVPBMT (_PAGE_NOCACHE_SVPBMT | _PAGE_IO_SVPBMT)
>
> +/*
> + * [63:59] T-Head Memory Type definitions:
> + *
> + * 00000 - NC Weakly-ordered, Non-cacheable, Non-bufferable, Non-shareable, Non-trustable
> + * 01110 - PMA Weakly-ordered, Cacheable, Bufferable, Shareable, Non-trustable
> + * 10000 - IO Strongly-ordered, Non-cacheable, Non-bufferable, Non-shareable, Non-trustable
> + */
> +#define _PAGE_PMA_THEAD ((1UL << 62) | (1UL << 61) | (1UL << 60))
> +#define _PAGE_NOCACHE_THEAD 0UL
> +#define _PAGE_IO_THEAD (1UL << 63)
> +#define _PAGE_MTMASK_THEAD (_PAGE_PMA_THEAD | _PAGE_IO_THEAD | (1UL << 59))
> +
> static inline u64 riscv_page_mtmask(void)
> {
> u64 val;
> @@ -193,7 +205,11 @@ static inline bool mm_pud_folded(struct mm_struct *mm)
>
> static inline pmd_t pfn_pmd(unsigned long pfn, pgprot_t prot)
> {
> - return __pmd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> + unsigned long prot_val = pgprot_val(prot);
> +
> + ALT_THEAD_PMA(prot_val);
> +
> + return __pmd((pfn << _PAGE_PFN_SHIFT) | prot_val);
> }
>
> static inline unsigned long _pmd_pfn(pmd_t pmd)
> diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
> index c55341b72de1..6f0a260d3f2c 100644
> --- a/arch/riscv/include/asm/pgtable.h
> +++ b/arch/riscv/include/asm/pgtable.h
> @@ -250,7 +250,11 @@ static inline void pmd_clear(pmd_t *pmdp)
>
> static inline pgd_t pfn_pgd(unsigned long pfn, pgprot_t prot)
> {
> - return __pgd((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> + unsigned long prot_val = pgprot_val(prot);
> +
> + ALT_THEAD_PMA(prot_val);
> +
> + return __pgd((pfn << _PAGE_PFN_SHIFT) | prot_val);
> }
>
> static inline unsigned long _pgd_pfn(pgd_t pgd)
> @@ -289,7 +293,11 @@ static inline unsigned long pte_pfn(pte_t pte)
> /* Constructs a page table entry */
> static inline pte_t pfn_pte(unsigned long pfn, pgprot_t prot)
> {
> - return __pte((pfn << _PAGE_PFN_SHIFT) | pgprot_val(prot));
> + unsigned long prot_val = pgprot_val(prot);
> +
> + ALT_THEAD_PMA(prot_val);
> +
> + return __pte((pfn << _PAGE_PFN_SHIFT) | prot_val);
> }
>
> #define mk_pte(page, prot) pfn_pte(page_to_pfn(page), prot)
> @@ -398,7 +406,11 @@ static inline int pmd_protnone(pmd_t pmd)
> /* Modify page protection bits */
> static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
> {
> - return __pte((pte_val(pte) & _PAGE_CHG_MASK) | pgprot_val(newprot));
> + unsigned long newprot_val = pgprot_val(newprot);
> +
> + ALT_THEAD_PMA(newprot_val);
> +
> + return __pte((pte_val(pte) & _PAGE_CHG_MASK) | newprot_val);
> }
>
> #define pgd_ERROR(e) \
> diff --git a/arch/riscv/include/asm/vendorid_list.h b/arch/riscv/include/asm/vendorid_list.h
> index 9d934215b3c8..cb89af3f0704 100644
> --- a/arch/riscv/include/asm/vendorid_list.h
> +++ b/arch/riscv/include/asm/vendorid_list.h
> @@ -6,5 +6,6 @@
> #define ASM_VENDOR_LIST_H
>
> #define SIFIVE_VENDOR_ID 0x489
> +#define THEAD_VENDOR_ID 0x5b7
>
> #endif
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index 0f8348ac30f1..bf3876a77ed7 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile
> @@ -14,6 +14,20 @@ ifdef CONFIG_KEXEC
> AFLAGS_kexec_relocate.o := -mcmodel=medany $(call cc-option,-mno-relax)
> endif
>
> +# cmodel=medany and notrace when patching early
> +ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
> +CFLAGS_alternative.o := -mcmodel=medany
> +CFLAGS_cpufeature.o := -mcmodel=medany
> +ifdef CONFIG_FTRACE
> +CFLAGS_REMOVE_alternative.o = $(CC_FLAGS_FTRACE)
> +CFLAGS_REMOVE_cpufeature.o = $(CC_FLAGS_FTRACE)
> +endif
> +ifdef CONFIG_KASAN
> +KASAN_SANITIZE_alternative.o := n
> +KASAN_SANITIZE_cpufeature.o := n
> +endif
> +endif
> +
> extra-y += head.o
> extra-y += vmlinux.lds
>
> diff --git a/arch/riscv/kernel/alternative.c b/arch/riscv/kernel/alternative.c
> index 27f722ae452b..c9d0d3c53223 100644
> --- a/arch/riscv/kernel/alternative.c
> +++ b/arch/riscv/kernel/alternative.c
> @@ -42,6 +42,11 @@ static void __init_or_module riscv_fill_cpu_mfr_info(struct cpu_manufacturer_inf
> case SIFIVE_VENDOR_ID:
> cpu_mfr_info->vendor_patch_func = sifive_errata_patch_func;
> break;
> +#endif
> +#ifdef CONFIG_ERRATA_THEAD
> + case THEAD_VENDOR_ID:
> + cpu_mfr_info->vendor_patch_func = thead_errata_patch_func;
> + break;
> #endif
> default:
> cpu_mfr_info->vendor_patch_func = NULL;
> @@ -82,6 +87,27 @@ void __init apply_boot_alternatives(void)
> RISCV_ALTERNATIVES_BOOT);
> }
>
> +/*
> + * apply_early_boot_alternatives() is called from setup_vm() with MMU-off.
> + *
> + * Following requirements should be honoured for it to work correctly:
> + * 1) It should use PC-relative addressing for accessing kernel symbols.
> + * To achieve this we always use GCC cmodel=medany.
> + * 2) The compiler instrumentation for FTRACE will not work for setup_vm()
> + * so disable compiler instrumentation when FTRACE is enabled.
> + *
> + * Currently, the above requirements are honoured by using custom CFLAGS
> + * for alternative.o in kernel/Makefile.
> + */
> +void __init apply_early_boot_alternatives(void)
> +{
> +#ifdef CONFIG_RISCV_ALTERNATIVE_EARLY
> + _apply_alternatives((struct alt_entry *)__alt_start,
> + (struct alt_entry *)__alt_end,
> + RISCV_ALTERNATIVES_EARLY_BOOT);
> +#endif
> +}
> +
> #ifdef CONFIG_MODULES
> void apply_module_alternatives(void *start, size_t length)
> {
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index f514b949c6a7..dea3ea19deee 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -254,7 +254,12 @@ struct cpufeature_info {
> static bool __init_or_module cpufeature_svpbmt_check_func(unsigned int stage)
> {
> #ifdef CONFIG_RISCV_ISA_SVPBMT
> - return riscv_isa_extension_available(NULL, SVPBMT);
> + switch (stage) {
> + case RISCV_ALTERNATIVES_EARLY_BOOT:
> + return false;
> + default:
> + return riscv_isa_extension_available(NULL, SVPBMT);
> + }
> #endif
>
> return false;
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index b0793dc0c291..45a4bf107bd2 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -936,6 +936,7 @@ asmlinkage void __init setup_vm(uintptr_t dtb_pa)
> BUG_ON((kernel_map.virt_addr + kernel_map.size) > ADDRESS_SPACE_END - SZ_4K);
> #endif
>
> + apply_early_boot_alternatives();
> pt_ops_set_early();
>
> /* Setup early PGD for fixmap */
> --
> 2.35.1
>

--
Best Regards
Guo Ren

ML: https://lore.kernel.org/linux-csky/