diff --git a/llvm/lib/Target/RISCV/RISCVSystemOperands.td b/llvm/lib/Target/RISCV/RISCVSystemOperands.td
--- a/llvm/lib/Target/RISCV/RISCVSystemOperands.td
+++ b/llvm/lib/Target/RISCV/RISCVSystemOperands.td
@@ -365,6 +365,7 @@
 //===-----------------------------------------------
 
 // Machine-level CSRs
+let FeaturesRequired = [{ {RISCV::FeatureStdExtSmaia} }] in {
 def : SysReg<"miselect", 0x350>;
 def : SysReg<"mireg", 0x351>;
 def : SysReg<"mtopei", 0x35C>;
@@ -378,8 +379,10 @@
 def : SysReg<"mviph", 0x319>;
 def : SysReg<"miph", 0x354>;
 } // isRV32Only
+}
 
 // Supervisor-level CSRs
+let FeaturesRequired = [{ {RISCV::FeatureStdExtSsaia} }] in {
 def : SysReg<"siselect", 0x150>;
 def : SysReg<"sireg", 0x151>;
 def : SysReg<"stopei", 0x15C>;
@@ -407,6 +410,7 @@
 def : SysReg<"vsieh", 0x214>;
 def : SysReg<"vsiph", 0x254>;
 } // isRV32Only
+}
 
 // Jump Vector Table CSR
 //===-----------------------------------------------
diff --git a/llvm/test/MC/RISCV/hypervisor-csr-names.s b/llvm/test/MC/RISCV/hypervisor-csr-names.s
--- a/llvm/test/MC/RISCV/hypervisor-csr-names.s
+++ b/llvm/test/MC/RISCV/hypervisor-csr-names.s
@@ -1,13 +1,13 @@
-# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-ssaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 #
-# RUN: llvm-mc %s -triple=riscv64 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+experimental-ssaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 
 ##################################
diff --git a/llvm/test/MC/RISCV/machine-csr-names.s b/llvm/test/MC/RISCV/machine-csr-names.s
--- a/llvm/test/MC/RISCV/machine-csr-names.s
+++ b/llvm/test/MC/RISCV/machine-csr-names.s
@@ -1,13 +1,13 @@
-# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-smaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+experimental-smaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-smaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 #
-# RUN: llvm-mc %s -triple=riscv64 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+experimental-smaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+experimental-smaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-smaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 
 ##################################
diff --git a/llvm/test/MC/RISCV/rv32-hypervisor-csr-names.s b/llvm/test/MC/RISCV/rv32-hypervisor-csr-names.s
--- a/llvm/test/MC/RISCV/rv32-hypervisor-csr-names.s
+++ b/llvm/test/MC/RISCV/rv32-hypervisor-csr-names.s
@@ -1,7 +1,7 @@
-# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-ssaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -mattr=+experimental-ssaia -triple riscv32 < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 
 ##################################
diff --git a/llvm/test/MC/RISCV/rv32-machine-csr-names.s b/llvm/test/MC/RISCV/rv32-machine-csr-names.s
--- a/llvm/test/MC/RISCV/rv32-machine-csr-names.s
+++ b/llvm/test/MC/RISCV/rv32-machine-csr-names.s
@@ -1,7 +1,7 @@
-# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-smaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -mattr=+experimental-smaia -triple riscv32 < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-smaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 
 ######################################
diff --git a/llvm/test/MC/RISCV/rv32-supervisor-csr-names.s b/llvm/test/MC/RISCV/rv32-supervisor-csr-names.s
--- a/llvm/test/MC/RISCV/rv32-supervisor-csr-names.s
+++ b/llvm/test/MC/RISCV/rv32-supervisor-csr-names.s
@@ -1,7 +1,7 @@
-# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-ssaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 
 ##################################
diff --git a/llvm/test/MC/RISCV/rvi-aliases-valid.s b/llvm/test/MC/RISCV/rvi-aliases-valid.s
--- a/llvm/test/MC/RISCV/rvi-aliases-valid.s
+++ b/llvm/test/MC/RISCV/rvi-aliases-valid.s
@@ -1,22 +1,22 @@
-# RUN: llvm-mc %s -triple=riscv32 -M no-aliases \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-ssaia -M no-aliases \
 # RUN:     | FileCheck -check-prefixes=CHECK-S-NOALIAS,CHECK-S-OBJ-NOALIAS %s
-# RUN: llvm-mc %s -triple=riscv32 \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-ssaia \
 # RUN:     | FileCheck -check-prefixes=CHECK-S,CHECK-S-OBJ %s
-# RUN: llvm-mc %s -triple=riscv64 -M no-aliases \
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+experimental-ssaia -M no-aliases \
 # RUN:     | FileCheck -check-prefixes=CHECK-S-NOALIAS,CHECK-S-OBJ-NOALIAS %s
-# RUN: llvm-mc %s -triple=riscv64 \
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+experimental-ssaia \
 # RUN:     | FileCheck -check-prefixes=CHECK-S,CHECK-S-OBJ %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d -r -M no-aliases - \
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d -r -M no-aliases - \
 # RUN:     | FileCheck -check-prefixes=CHECK-OBJ-NOALIAS,CHECK-S-OBJ-NOALIAS %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d -r - \
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d -r - \
 # RUN:     | FileCheck -check-prefixes=CHECK-OBJ,CHECK-S-OBJ %s
-# RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
-# RUN:     | llvm-objdump -d -r -M no-aliases - \
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d -r -M no-aliases - \
 # RUN:     | FileCheck -check-prefixes=CHECK-OBJ-NOALIAS,CHECK-S-OBJ-NOALIAS %s
-# RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
-# RUN:     | llvm-objdump -d -r - \
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+experimental-ssaia< %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d -r - \
 # RUN:     | FileCheck -check-prefixes=CHECK-OBJ,CHECK-S-OBJ %s
 
 # The following check prefixes are used in this test:
diff --git a/llvm/test/MC/RISCV/supervisor-csr-names.s b/llvm/test/MC/RISCV/supervisor-csr-names.s
--- a/llvm/test/MC/RISCV/supervisor-csr-names.s
+++ b/llvm/test/MC/RISCV/supervisor-csr-names.s
@@ -1,13 +1,13 @@
-# RUN: llvm-mc %s -triple=riscv32 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv32 -mattr=+experimental-ssaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv32 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv32 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d - \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 #
-# RUN: llvm-mc %s -triple=riscv64 -riscv-no-aliases -show-encoding \
+# RUN: llvm-mc %s -triple=riscv64 -mattr=+experimental-ssaia -riscv-no-aliases -show-encoding \
 # RUN:     | FileCheck -check-prefixes=CHECK-INST,CHECK-ENC %s
-# RUN: llvm-mc -filetype=obj -triple riscv64 < %s \
-# RUN:     | llvm-objdump -d - \
+# RUN: llvm-mc -filetype=obj -triple riscv64 -mattr=+experimental-ssaia < %s \
+# RUN:     | llvm-objdump --mattr=+experimental-ssaia -d -  \
 # RUN:     | FileCheck -check-prefix=CHECK-INST-ALIAS %s
 
 ##################################