[PATCH v3 2/2] target/riscv: UPDATE xATP write CSR

[Irina Ryapolova]

Added xATP_MODE validation for vsatp/hgatp CSRs.
The xATP register is an SXLEN-bit read/write WARL register, so
the legal value must be returned (See riscv-privileged-20211203, 
SATP/VSATP/HGATP CSRs).

Signed-off-by: Irina Ryapolova <irina.ryapolova@syntacore.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/csr.c | 52 ++++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 735fb27be7..6d7a3dd9aa 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -1282,6 +1282,32 @@ static bool validate_vm(CPURISCVState *env, target_ulong 
vm)
     return get_field(mode_supported, (1 << vm));
 }
 
+static target_ulong legalize_xatp(CPURISCVState *env, target_ulong old_xatp,
+                                  target_ulong val)
+{
+    target_ulong mask;
+    bool vm;
+    if (riscv_cpu_mxl(env) == MXL_RV32) {
+        vm = validate_vm(env, get_field(val, SATP32_MODE));
+        mask = (val ^ old_xatp) & (SATP32_MODE | SATP32_ASID | SATP32_PPN);
+    } else {
+        vm = validate_vm(env, get_field(val, SATP64_MODE));
+        mask = (val ^ old_xatp) & (SATP64_MODE | SATP64_ASID | SATP64_PPN);
+    }
+
+    if (vm && mask) {
+        /*
+         * The ISA defines SATP.MODE=Bare as "no translation", but we still
+         * pass these through QEMU's TLB emulation as it improves
+         * performance.  Flushing the TLB on SATP writes with paging
+         * enabled avoids leaking those invalid cached mappings.
+         */
+        tlb_flush(env_cpu(env));
+        return val;
+    }
+    return old_xatp;
+}
+
 static target_ulong legalize_mpp(CPURISCVState *env, target_ulong old_mpp,
                                  target_ulong val)
 {
@@ -2997,31 +3023,11 @@ static RISCVException read_satp(CPURISCVState *env, int 
csrno,
 static RISCVException write_satp(CPURISCVState *env, int csrno,
                                  target_ulong val)
 {
-    target_ulong mask;
-    bool vm;
-
     if (!riscv_cpu_cfg(env)->mmu) {
         return RISCV_EXCP_NONE;
     }
 
-    if (riscv_cpu_mxl(env) == MXL_RV32) {
-        vm = validate_vm(env, get_field(val, SATP32_MODE));
-        mask = (val ^ env->satp) & (SATP32_MODE | SATP32_ASID | SATP32_PPN);
-    } else {
-        vm = validate_vm(env, get_field(val, SATP64_MODE));
-        mask = (val ^ env->satp) & (SATP64_MODE | SATP64_ASID | SATP64_PPN);
-    }
-
-    if (vm && mask) {
-        /*
-         * The ISA defines SATP.MODE=Bare as "no translation", but we still
-         * pass these through QEMU's TLB emulation as it improves
-         * performance.  Flushing the TLB on SATP writes with paging
-         * enabled avoids leaking those invalid cached mappings.
-         */
-        tlb_flush(env_cpu(env));
-        env->satp = val;
-    }
+    env->satp = legalize_xatp(env, env->satp, val);
     return RISCV_EXCP_NONE;
 }
 
@@ -3506,7 +3512,7 @@ static RISCVException read_hgatp(CPURISCVState *env, int 
csrno,
 static RISCVException write_hgatp(CPURISCVState *env, int csrno,
                                   target_ulong val)
 {
-    env->hgatp = val;
+    env->hgatp = legalize_xatp(env, env->hgatp, val);
     return RISCV_EXCP_NONE;
 }
 
@@ -3772,7 +3778,7 @@ static RISCVException read_vsatp(CPURISCVState *env, int 
csrno,
 static RISCVException write_vsatp(CPURISCVState *env, int csrno,
                                   target_ulong val)
 {
-    env->vsatp = val;
+    env->vsatp = legalize_xatp(env, env->vsatp, val);
     return RISCV_EXCP_NONE;
 }
 
-- 
2.25.1