target/riscv/tcg: disable svnapot if satp_mode < sv39

We did a recent change to disable svpbmt if satp_mode < sv39 that was
discovered via a gitlab report.

This time we don't have an opened bug but the problem is similar: RISC-V
privileged ISA, chapter '"Svnapot" Extension for NAPOT Translation
Contiguity, Version 1.0' states:

"The Svnapot extension depends on the Sv39 extension."

Do the same thing with svnapot, including the user warning in case we
try to enable it without the required satp_mode:

$ ./build/qemu-system-riscv64 -M virt,dumpdtb=fdt.dtb \
     -cpu max,sv39=off,sv48=off,sv57=off,sv64=off,svnapot=on
qemu-system-riscv64: warning: svnapot requires at least satp sv39, current satp mode: none

Signed-off-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20260527213034.2094103-1-daniel.barboza@oss.qualcomm.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
(cherry picked from commit 601c8494c6c7e73f5b3f30b5823de2c13c003990)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

1 files changed, 10 insertions, 0 deletions

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index c4dfa4ac09..8f8da3e612 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -871,6 +871,16 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
                                      riscv_cpu_is_32bit(cpu)));
         }
     }
+
+    if (cpu->cfg.ext_svnapot && cpu->cfg.max_satp_mode < VM_1_10_SV39) {
+        cpu->cfg.ext_svnapot = false;
+        if (cpu_cfg_ext_is_user_set(CPU_CFG_OFFSET(ext_svnapot))) {
+            warn_report("svnapot requires at least satp sv39, "
+                        "current satp mode: %s",
+                        satp_mode_str(cpu->cfg.max_satp_mode,
+                                      riscv_cpu_is_32bit(cpu)));
+        }
+    }
 #endif
     /*
      * Disable isa extensions based on priv spec after we