--- /dev/null
+From 4774848fef6041716a4883217eb75f6b10eb183b Mon Sep 17 00:00:00 2001
+From: Samuel Holland <samuel.holland@sifive.com>
+Date: Tue, 27 Feb 2024 22:55:34 -0800
+Subject: riscv: Add a custom ISA extension for the [ms]envcfg CSR
+
+From: Samuel Holland <samuel.holland@sifive.com>
+
+commit 4774848fef6041716a4883217eb75f6b10eb183b upstream.
+
+The [ms]envcfg CSR was added in version 1.12 of the RISC-V privileged
+ISA (aka S[ms]1p12). However, bits in this CSR are defined by several
+other extensions which may be implemented separately from any particular
+version of the privileged ISA (for example, some unrelated errata may
+prevent an implementation from claiming conformance with Ss1p12). As a
+result, Linux cannot simply use the privileged ISA version to determine
+if the CSR is present. It must also check if any of these other
+extensions are implemented. It also cannot probe the existence of the
+CSR at runtime, because Linux does not require Sstrict, so (in the
+absence of additional information) it cannot know if a CSR at that
+address is [ms]envcfg or part of some non-conforming vendor extension.
+
+Since there are several standard extensions that imply the existence of
+the [ms]envcfg CSR, it becomes unwieldy to check for all of them
+wherever the CSR is accessed. Instead, define a custom Xlinuxenvcfg ISA
+extension bit that is implied by the other extensions and denotes that
+the CSR exists as defined in the privileged ISA, containing at least one
+of the fields common between menvcfg and senvcfg.
+
+This extension does not need to be parsed from the devicetree or ISA
+string because it can only be implemented as a subset of some other
+standard extension.
+
+Cc: <stable@vger.kernel.org> # v6.7+
+Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
+Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
+Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
+Link: https://lore.kernel.org/r/20240228065559.3434837-3-samuel.holland@sifive.com
+Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
+Cc: Ron Economos <re@w6rz.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/riscv/include/asm/hwcap.h | 2 ++
+ arch/riscv/kernel/cpufeature.c | 14 ++++++++++++--
+ 2 files changed, 14 insertions(+), 2 deletions(-)
+
+--- a/arch/riscv/include/asm/hwcap.h
++++ b/arch/riscv/include/asm/hwcap.h
+@@ -58,6 +58,8 @@
+ #define RISCV_ISA_EXT_SMSTATEEN 43
+ #define RISCV_ISA_EXT_ZICOND 44
+
++#define RISCV_ISA_EXT_XLINUXENVCFG 127
++
+ #define RISCV_ISA_EXT_MAX 64
+
+ #ifdef CONFIG_RISCV_M_MODE
+--- a/arch/riscv/kernel/cpufeature.c
++++ b/arch/riscv/kernel/cpufeature.c
+@@ -115,6 +115,16 @@ static bool riscv_isa_extension_check(in
+ }
+
+ /*
++ * While the [ms]envcfg CSRs were not defined until version 1.12 of the RISC-V
++ * privileged ISA, the existence of the CSRs is implied by any extension which
++ * specifies [ms]envcfg bit(s). Hence, we define a custom ISA extension for the
++ * existence of the CSR, and treat it as a subset of those other extensions.
++ */
++static const unsigned int riscv_xlinuxenvcfg_exts[] = {
++ RISCV_ISA_EXT_XLINUXENVCFG
++};
++
++/*
+ * The canonical order of ISA extension names in the ISA string is defined in
+ * chapter 27 of the unprivileged specification.
+ *
+@@ -167,8 +177,8 @@ const struct riscv_isa_ext_data riscv_is
+ __RISCV_ISA_EXT_DATA(p, RISCV_ISA_EXT_p),
+ __RISCV_ISA_EXT_DATA(v, RISCV_ISA_EXT_v),
+ __RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
+- __RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
+- __RISCV_ISA_EXT_DATA(zicboz, RISCV_ISA_EXT_ZICBOZ),
++ __RISCV_ISA_EXT_SUPERSET(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts),
++ __RISCV_ISA_EXT_SUPERSET(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts),
+ __RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
+ __RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND),
+ __RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),