[PATCH] RISC-V: errata: Add SiFive MAL-9092 workaround

[Yong-Xuan Wang]

SiFive cores with MAL-9092 require fence.rw instructions around
HLV/HLVX/HSV hypervisor instructions to ensure proper memory ordering
when accessing guest memory.

Note that HSTATUS.HU is cleared during KVM initialization, restricting
hypervisor instructions to HS-mode only. If future changes enable
HSTATUS.HU for U-mode access, additional errata considerations will be
needed.

Signed-off-by: Yong-Xuan Wang <yongxuan.wang at sifive.com>
Reviewed-by: Samuel Holland <samuel.holland at sifive.com>
---
 arch/riscv/Kconfig.errata                    | 14 ++++++++++++++
 arch/riscv/errata/sifive/errata.c            | 20 ++++++++++++++++++++
 arch/riscv/include/asm/errata_list_vendors.h |  3 ++-
 arch/riscv/include/asm/insn-def.h            | 16 +++++++++++++---
 4 files changed, 49 insertions(+), 4 deletions(-)

diff --git a/arch/riscv/Kconfig.errata b/arch/riscv/Kconfig.errata
index 3c945d086c7d..a94e7da629d2 100644
--- a/arch/riscv/Kconfig.errata
+++ b/arch/riscv/Kconfig.errata
@@ -96,6 +96,20 @@ config ERRATA_STARFIVE_JH7100
 	  Say "Y" if you want to support the BeagleV Starlight and/or
 	  StarFive VisionFive V1 boards.
 
+config ERRATA_SIFIVE_MAL_9092
+	bool "Apply SiFive HLV/HLVX/HSV fence errata"
+	depends on ERRATA_SIFIVE && 64BIT
+	default y
+	help
+	  This will apply the SiFive MAL-9092 errata to add fence.rw
+	  instructions around all HLV/HLVX/HSV instructions.
+
+	  Note: HSTATUS.HU is cleared during KVM initialization. If future
+	  changes enable HSTATUS.HU to allow hypervisor instructions in
+	  U-mode, additional errata handling may be required.
+
+	  If you don't know what to do here, say "Y".
+
 config ERRATA_THEAD
 	bool "T-HEAD errata"
 	depends on RISCV_ALTERNATIVE
diff --git a/arch/riscv/errata/sifive/errata.c b/arch/riscv/errata/sifive/errata.c
index df80c9614df1..1a5d223ebf35 100644
--- a/arch/riscv/errata/sifive/errata.c
+++ b/arch/riscv/errata/sifive/errata.c
@@ -51,6 +51,22 @@ static bool errata_cip_1200_check_func(unsigned long  arch_id, unsigned long imp
 	return true;
 }
 
+static bool errata_mal_9092_check_func(unsigned long  arch_id, unsigned long impid)
+{
+	/*
+	 * Affected cores:
+	 * Architecture ID: 0x8000000000000109
+	 * Implementation ID: 0x19251031, 0x19251217, 0x19260320
+	 */
+
+	if (arch_id != 0x8000000000000109)
+		return false;
+	if (impid != 0x19251031 && impid != 0x19251217 && impid != 0x19260320)
+		return false;
+
+	return true;
+}
+
 static struct errata_info_t errata_list[ERRATA_SIFIVE_NUMBER] = {
 	{
 		.name = "cip-453",
@@ -60,6 +76,10 @@ static struct errata_info_t errata_list[ERRATA_SIFIVE_NUMBER] = {
 		.name = "cip-1200",
 		.check_func = errata_cip_1200_check_func
 	},
+	{
+		.name = "mal-9092",
+		.check_func = errata_mal_9092_check_func
+	},
 };
 
 static u32 __init_or_module sifive_errata_probe(unsigned long archid,
diff --git a/arch/riscv/include/asm/errata_list_vendors.h b/arch/riscv/include/asm/errata_list_vendors.h
index ec7eba373437..c62a82f60468 100644
--- a/arch/riscv/include/asm/errata_list_vendors.h
+++ b/arch/riscv/include/asm/errata_list_vendors.h
@@ -11,7 +11,8 @@
 #ifdef CONFIG_ERRATA_SIFIVE
 #define	ERRATA_SIFIVE_CIP_453 0
 #define	ERRATA_SIFIVE_CIP_1200 1
-#define	ERRATA_SIFIVE_NUMBER 2
+#define	ERRATA_SIFIVE_MAL_9092 2
+#define	ERRATA_SIFIVE_NUMBER 3
 #endif
 
 #ifdef CONFIG_ERRATA_THEAD
diff --git a/arch/riscv/include/asm/insn-def.h b/arch/riscv/include/asm/insn-def.h
index 7c6daf116756..8fcc848c196e 100644
--- a/arch/riscv/include/asm/insn-def.h
+++ b/arch/riscv/include/asm/insn-def.h
@@ -192,18 +192,28 @@
 	INSN_R(OPCODE_SYSTEM, FUNC3(0), FUNC7(49),		\
 	       __RD(0), RS1(gaddr), RS2(vmid))
 
+#define ALT_SIFIVE_MAL_9092_FENCE					\
+ALTERNATIVE("nop", "fence rw, rw", SIFIVE_VENDOR_ID,			\
+	    ERRATA_SIFIVE_MAL_9092, CONFIG_ERRATA_SIFIVE_MAL_9092)
+
 #define HLVX_HU(dest, addr)					\
+	ALT_SIFIVE_MAL_9092_FENCE "\n"				\
 	INSN_R(OPCODE_SYSTEM, FUNC3(4), FUNC7(50),		\
-	       RD(dest), RS1(addr), __RS2(3))
+	       RD(dest), RS1(addr), __RS2(3)) "\n"		\
+	ALT_SIFIVE_MAL_9092_FENCE
 
 #define HLV_W(dest, addr)					\
+	ALT_SIFIVE_MAL_9092_FENCE "\n"				\
 	INSN_R(OPCODE_SYSTEM, FUNC3(4), FUNC7(52),		\
-	       RD(dest), RS1(addr), __RS2(0))
+	       RD(dest), RS1(addr), __RS2(0)) "\n"		\
+	ALT_SIFIVE_MAL_9092_FENCE
 
 #ifdef CONFIG_64BIT
 #define HLV_D(dest, addr)					\
+	ALT_SIFIVE_MAL_9092_FENCE "\n"				\
 	INSN_R(OPCODE_SYSTEM, FUNC3(4), FUNC7(54),		\
-	       RD(dest), RS1(addr), __RS2(0))
+	       RD(dest), RS1(addr), __RS2(0)) "\n"		\
+	ALT_SIFIVE_MAL_9092_FENCE
 #else
 #define HLV_D(dest, addr)					\
 	__ASM_STR(.error "hlv.d requires 64-bit support")

---
base-commit: 8da45c93dfa98f25b148512d92ecfa75d027a5cc
change-id: 20260816-sifive-errata-0aa5829c2234