[RFC patch 4/4] riscv: sifive: apply errata "cip-453" patch
Vincent Chen
vincent.chen at sifive.com
Mon Mar 8 03:58:17 GMT 2021
Add sign extension to the $badaddr before addressing the instruction page
fault and instruction access fault to workaround the issue "cip-453".
To avoid affecting the existing code sequence, this patch will creates two
trampolines to add sign extension to the $badaddr. By the "alternative"
mechanism, these two trampolines will replace the original exception
handler of instruction page fault and instruction access fault in the
excp_vect_table. In this case, only the specific SiFive CPU core jumps to
the do_page_fault and do_trap_insn_fault through these two trampolines.
Other CPUs are not affected.
Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
---
arch/riscv/Kconfig.erratas | 20 +++++++++++
arch/riscv/Kconfig.socs | 1 +
arch/riscv/errata/Makefile | 1 +
arch/riscv/errata/sifive/Makefile | 2 ++
arch/riscv/errata/sifive/errata.c | 56 +++++++++++++++++++++++++++++++
arch/riscv/errata/sifive/errata_cip_453.S | 34 +++++++++++++++++++
arch/riscv/include/asm/errata_list.h | 3 +-
arch/riscv/kernel/entry.S | 12 +++++--
8 files changed, 126 insertions(+), 3 deletions(-)
create mode 100644 arch/riscv/errata/sifive/Makefile
create mode 100644 arch/riscv/errata/sifive/errata.c
create mode 100644 arch/riscv/errata/sifive/errata_cip_453.S
diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
index 4d0bafc536df..907fa6b13ee2 100644
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -9,4 +9,24 @@ config RISCV_ERRATA_ALTERNATIVE
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"
+ help
+ All SiFive errata Kconfig depend on this Kconfig. Please say "Y"
+ here if your platform uses SiFive CPU cores.
+
+ Otherwise, please say "N" here to avoid unnecessary overhead.
+
+config ERRATA_SIFIVE_CIP_453
+ bool "Apply SiFive errata CIP-453"
+ depends on ERRATA_SIFIVE
+ depends on RISCV_ERRATA_ALTERNATIVE
+ default y
+ help
+ This will apply the SiFive CIP-453 errata to add sign extension
+ to the $badaddr when exception type is instruction page fault
+ and instruction access fault.
+
+ If you don't know what to do here, say "Y".
+
endmenu
diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
index 7efcece8896c..b9eda857fc87 100644
--- a/arch/riscv/Kconfig.socs
+++ b/arch/riscv/Kconfig.socs
@@ -7,6 +7,7 @@ config SOC_SIFIVE
select CLK_SIFIVE
select CLK_SIFIVE_PRCI
select SIFIVE_PLIC
+ select ERRATA_SIFIVE
help
This enables support for SiFive SoC platform hardware.
diff --git a/arch/riscv/errata/Makefile b/arch/riscv/errata/Makefile
index 43e6d5424367..b8f8740a3e44 100644
--- a/arch/riscv/errata/Makefile
+++ b/arch/riscv/errata/Makefile
@@ -1 +1,2 @@
obj-y += alternative.o
+obj-$(CONFIG_ERRATA_SIFIVE) += sifive/
diff --git a/arch/riscv/errata/sifive/Makefile b/arch/riscv/errata/sifive/Makefile
new file mode 100644
index 000000000000..b7f4cd7ee185
--- /dev/null
+++ b/arch/riscv/errata/sifive/Makefile
@@ -0,0 +1,2 @@
+obj-y += altern_ops.o
+obj-y += errata_cip_453.o
diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
new file mode 100644
index 000000000000..0b0a9af42a55
--- /dev/null
+++ b/arch/riscv/errata/sifive/errata.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 Sifive.
+ */
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/bug.h>
+#include <asm/alternative.h>
+#include <asm/vendorid_list.h>
+#include <asm/errata_list.h>
+
+#define MAX_ERRATA_IMPID 5
+struct errata_info_t {
+ char name[ERRATA_STRING_LENGTH_MAX];
+ unsigned long arch_id;
+ unsigned long imp_id[MAX_ERRATA_IMPID];
+} errata_info;
+
+struct errata_info_t sifive_errata_list[ERRATA_NUMBER] = {
+ {
+ .name = "cip-453",
+ .arch_id = 0x8000000000000007,
+ .imp_id = {
+ 0x20181004, 0x00200504
+ },
+ },
+};
+
+static inline bool __init cpu_info_cmp(struct errata_info_t *errata, struct alt_entry *alt)
+{
+ int i;
+
+ if (errata->arch_id != cpu_mfr_info.arch_id)
+ return false;
+
+ for (i = 0; i < MAX_ERRATA_IMPID && errata->imp_id[i]; i++)
+ if (errata->imp_id[i] == cpu_mfr_info.imp_id)
+ return true;
+
+ return false;
+}
+
+static bool __init sifive_errata_check(struct alt_entry *alt)
+{
+ if (cpu_mfr_info.vendor_id != alt->vendor_id)
+ return false;
+
+ if (likely(alt->errata_id < ERRATA_NUMBER))
+ return cpu_info_cmp(&sifive_errata_list[alt->errata_id], alt);
+
+ WARN_ON(1);
+ return false;
+}
+
+REGISTER_ERRATA_CHECKFUNC(sifive_errata_check, SIFIVE_VENDOR_ID);
diff --git a/arch/riscv/errata/sifive/errata_cip_453.S b/arch/riscv/errata/sifive/errata_cip_453.S
new file mode 100644
index 000000000000..34d0fe26172e
--- /dev/null
+++ b/arch/riscv/errata/sifive/errata_cip_453.S
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 SiFive
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/alternative.h>
+
+.macro ADD_SIGN_EXT pt_reg badaddr tmp_reg
+ REG_L \badaddr, PT_BADADDR(\pt_reg)
+ li \tmp_reg,1
+ slli \tmp_reg,\tmp_reg,0x26
+ and \tmp_reg,\tmp_reg,\badaddr
+ beqz \tmp_reg, 1f
+ li \tmp_reg,-1
+ slli \tmp_reg,\tmp_reg,0x27
+ or \badaddr,\tmp_reg,\badaddr
+ REG_S \badaddr, PT_BADADDR(\pt_reg)
+1:
+.endm
+
+ENTRY(do_page_fault_trampoline)
+ ADD_SIGN_EXT a0, t0, t1
+ la t0, do_page_fault
+ jr t0
+END(do_page_fault_trampoline)
+
+ENTRY(do_trap_insn_fault_trampoline)
+ ADD_SIGN_EXT a0, t0, t1
+ la t0, do_trap_insn_fault
+ jr t0
+END(do_trap_insn_fault_trampoline)
diff --git a/arch/riscv/include/asm/errata_list.h b/arch/riscv/include/asm/errata_list.h
index 5e5a1fcd90ba..d3752c8eff1f 100644
--- a/arch/riscv/include/asm/errata_list.h
+++ b/arch/riscv/include/asm/errata_list.h
@@ -4,5 +4,6 @@
*/
#ifdef CONFIG_SOC_SIFIVE
-#define ERRATA_NUMBER 0
+#define ERRATA_CIP_453 0
+#define ERRATA_NUMBER 1
#endif
diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
index 744f3209c48d..821e86ee67e4 100644
--- a/arch/riscv/kernel/entry.S
+++ b/arch/riscv/kernel/entry.S
@@ -12,6 +12,9 @@
#include <asm/unistd.h>
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
+#include <asm/alternative.h>
+#include <asm/vendorid_list.h>
+#include <asm/errata_list.h>
#if !IS_ENABLED(CONFIG_PREEMPTION)
.set resume_kernel, restore_all
@@ -450,7 +453,9 @@ ENDPROC(__switch_to)
/* Exception vector table */
ENTRY(excp_vect_table)
RISCV_PTR do_trap_insn_misaligned
- RISCV_PTR do_trap_insn_fault
+ ALTERNATIVE(__stringify(RISCV_PTR do_trap_insn_fault),
+ __stringify(RISCV_PTR do_trap_insn_fault_trampoline),
+ SIFIVE_VENDOR_ID, ERRATA_CIP_453, CONFIG_ERRATA_SIFIVE_CIP_453)
RISCV_PTR do_trap_insn_illegal
RISCV_PTR do_trap_break
RISCV_PTR do_trap_load_misaligned
@@ -461,7 +466,10 @@ ENTRY(excp_vect_table)
RISCV_PTR do_trap_ecall_s
RISCV_PTR do_trap_unknown
RISCV_PTR do_trap_ecall_m
- RISCV_PTR do_page_fault /* instruction page fault */
+ /* instruciton page fault */
+ ALTERNATIVE(__stringify(RISCV_PTR do_page_fault),
+ __stringify(RISCV_PTR do_page_fault_trampoline),
+ SIFIVE_VENDOR_ID, ERRATA_CIP_453, CONFIG_ERRATA_SIFIVE_CIP_453)
RISCV_PTR do_page_fault /* load page fault */
RISCV_PTR do_trap_unknown
RISCV_PTR do_page_fault /* store page fault */
--
2.7.4
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