[PATCH v5 14/14] riscv: add memory-type errata for T-Head

Heiko Stuebner
2022-01-21T16:38:30Z

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>
---
arch/riscv/Kconfig.erratas | 19 ++++++
arch/riscv/errata/Makefile | 1 +
arch/riscv/errata/sifive/errata.c | 7 ++-
arch/riscv/errata/thead/Makefile | 1 +
arch/riscv/errata/thead/errata.c | 85 ++++++++++++++++++++++++++
arch/riscv/include/asm/alternative.h | 5 ++
arch/riscv/include/asm/errata_list.h | 47 ++++++++++++--
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/alternative.c | 14 +++++
arch/riscv/kernel/cpufeature.c | 2 +
arch/riscv/mm/init.c | 2 +
13 files changed, 211 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.erratas b/arch/riscv/Kconfig.erratas
index d18be8ff0245..380ec039c3dc 100644
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -31,4 +31,23 @@ config ERRATA_SIFIVE_CIP_1200

If you don't know what to do here, say "Y".

+config ERRATA_THEAD
+ bool "T-HEAD errata"
+ 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.
+
+ If you don't know what to do here, say "Y".
+
+config ERRATA_THEAD_PBMT
+ bool "Apply T-Head memory type errata"
+ depends on ERRATA_THEAD && 64BIT
+ 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 4fe03ac41fd7..f933d6cdf304 100644
--- a/arch/riscv/errata/sifive/errata.c
+++ b/arch/riscv/errata/sifive/errata.c
@@ -84,10 +84,15 @@ void __init sifive_errata_patch_func(struct alt_entry *begin, struct alt_entry *
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..2d644e19caef
--- /dev/null
+++ b/arch/riscv/errata/thead/Makefile
@@ -0,0 +1 @@
+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..fd8e0538a3f0
--- /dev/null
+++ b/arch/riscv/errata/thead/errata.c
@@ -0,0 +1,85 @@
+// 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 cpu_apply_errata = 0;
+ 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);
+
+ cpu_apply_errata |= tmp;
+ }
+ }
+
+ 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 cf3b22173834..d1154c91ab03 100644
--- a/arch/riscv/include/asm/alternative.h
+++ b/arch/riscv/include/asm/alternative.h
@@ -19,8 +19,10 @@

#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 {
@@ -39,6 +41,9 @@ 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);
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index a4a9b0842922..4fac46b82c16 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

@@ -42,10 +47,44 @@ asm(ALTERNATIVE("sfence.vma %0", "sfence.vma", SIFIVE_VENDOR_ID, \
* in the default case.
*/
#define ALT_SVPBMT_SHIFT 61
-#define ALT_SVPBMT(_val, prot) \
-asm(ALTERNATIVE("li %0, 0\t\nnop", "li %0, %1\t\nslli %0,%0,%2", 0, \
- CPUFEATURE_SVPBMT, CONFIG_64BIT) \
- : "=r"(_val) : "I"(prot##_SVPBMT >> ALT_SVPBMT_SHIFT), "I"(ALT_SVPBMT_SHIFT))
+#define ALT_THEAD_PBMT_SHIFT 59
+#define ALT_SVPBMT(_val, prot) \
+asm(ALTERNATIVE_2("li %0, 0\t\nnop", \
+ "li %0, %1\t\nslli %0,%0,%3", 0, CPUFEATURE_SVPBMT, CONFIG_64BIT, \
+ "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"(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 58b34ef74acb..e7ce01cdc235 100644
--- a/arch/riscv/include/asm/pgtable-64.h
+++ b/arch/riscv/include/asm/pgtable-64.h
@@ -49,6 +49,18 @@ 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;
@@ -126,7 +138,11 @@ static inline struct page *pud_page(pud_t pud)

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 a189a21a7c8a..c3b9220b2523 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -219,7 +219,11 @@ 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)
@@ -258,7 +262,11 @@ 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)
@@ -367,7 +375,11 @@ 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/alternative.c b/arch/riscv/kernel/alternative.c
index 54913857b682..e272599f96ef 100644
--- a/arch/riscv/kernel/alternative.c
+++ b/arch/riscv/kernel/alternative.c
@@ -48,6 +48,11 @@ static void __init init_alternative(void)
case SIFIVE_VENDOR_ID:
vendor_patch_func = sifive_errata_patch_func;
break;
+#endif
+#ifdef CONFIG_ERRATA_THEAD
+ case THEAD_VENDOR_ID:
+ vendor_patch_func = thead_errata_patch_func;
+ break;
#endif
default:
vendor_patch_func = NULL;
@@ -85,6 +90,15 @@ void __init apply_boot_alternatives(void)
RISCV_ALTERNATIVES_BOOT);
}

+void __init apply_early_boot_alternatives(void)
+{
+ init_alternative();
+
+ _apply_alternatives((struct alt_entry *)__alt_start,
+ (struct alt_entry *)__alt_end,
+ RISCV_ALTERNATIVES_EARLY_BOOT);
+}
+
#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 d14289fba055..4ed18981d94d 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -224,6 +224,8 @@ static bool cpufeature_svpbmt_check_func(unsigned int stage)

#if defined(CONFIG_MMU) && defined(CONFIG_64BIT)
switch (stage) {
+ case RISCV_ALTERNATIVES_EARLY_BOOT:
+ return false;
case RISCV_ALTERNATIVES_BOOT:
return cpufeature_svpbmt_check_fdt();
default:
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 24b2b8044602..063d5f022a05 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -624,6 +624,8 @@ 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.alloc_pte = alloc_pte_early;
pt_ops.get_pte_virt = get_pte_virt_early;
#ifndef __PAGETABLE_PMD_FOLDED
--
2.30.2