target: riscv: Add Svrsw60t59b extension support

The Svrsw60t59b extension allows to free the PTE reserved bits 60 and 59
for software to use.

Reviewed-by: Deepak Gupta <debug@rivosinc.com>
Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Reviewed-by: Nutty Liu<liujingqi@lanxincomputing.com>
Message-ID: <20250702-dev-alex-svrsw60b59b_v2-v2-1-504ddf0f8530@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/riscv-iommu-bits.h

@@ -79,6 +79,7 @@ struct riscv_iommu_pq_record {
 #define RISCV_IOMMU_CAP_SV39            BIT_ULL(9)
 #define RISCV_IOMMU_CAP_SV48            BIT_ULL(10)
 #define RISCV_IOMMU_CAP_SV57            BIT_ULL(11)
+#define RISCV_IOMMU_CAP_SVRSW60T59B     BIT_ULL(14)
 #define RISCV_IOMMU_CAP_SV32X4          BIT_ULL(16)
 #define RISCV_IOMMU_CAP_SV39X4          BIT_ULL(17)
 #define RISCV_IOMMU_CAP_SV48X4          BIT_ULL(18)

hw/riscv/riscv-iommu.c

@@ -2351,7 +2351,8 @@ static void riscv_iommu_realize(DeviceState *dev, Error **errp)
     }
     if (s->enable_g_stage) {
         s->cap |= RISCV_IOMMU_CAP_SV32X4 | RISCV_IOMMU_CAP_SV39X4 |
-                  RISCV_IOMMU_CAP_SV48X4 | RISCV_IOMMU_CAP_SV57X4;
+                  RISCV_IOMMU_CAP_SV48X4 | RISCV_IOMMU_CAP_SV57X4 |
+                  RISCV_IOMMU_CAP_SVRSW60T59B;
     }
 
     if (s->hpm_cntrs > 0) {

target/riscv/cpu.c

@@ -230,6 +230,7 @@ const RISCVIsaExtData isa_edata_arr[] = {
     ISA_EXT_DATA_ENTRY(svinval, PRIV_VERSION_1_12_0, ext_svinval),
     ISA_EXT_DATA_ENTRY(svnapot, PRIV_VERSION_1_12_0, ext_svnapot),
     ISA_EXT_DATA_ENTRY(svpbmt, PRIV_VERSION_1_12_0, ext_svpbmt),
+    ISA_EXT_DATA_ENTRY(svrsw60t59b, PRIV_VERSION_1_13_0, ext_svrsw60t59b),
     ISA_EXT_DATA_ENTRY(svukte, PRIV_VERSION_1_13_0, ext_svukte),
     ISA_EXT_DATA_ENTRY(svvptc, PRIV_VERSION_1_13_0, ext_svvptc),
     ISA_EXT_DATA_ENTRY(xtheadba, PRIV_VERSION_1_11_0, ext_xtheadba),
@@ -1285,6 +1286,7 @@ const RISCVCPUMultiExtConfig riscv_cpu_extensions[] = {
     MULTI_EXT_CFG_BOOL("svinval", ext_svinval, false),
     MULTI_EXT_CFG_BOOL("svnapot", ext_svnapot, false),
     MULTI_EXT_CFG_BOOL("svpbmt", ext_svpbmt, false),
+    MULTI_EXT_CFG_BOOL("svrsw60t59b", ext_svrsw60t59b, false),
     MULTI_EXT_CFG_BOOL("svvptc", ext_svvptc, true),
 
     MULTI_EXT_CFG_BOOL("zicntr", ext_zicntr, true),

target/riscv/cpu_bits.h

@@ -735,7 +735,8 @@ typedef enum {
 #define PTE_SOFT            0x300 /* Reserved for Software */
 #define PTE_PBMT            0x6000000000000000ULL /* Page-based memory types */
 #define PTE_N               0x8000000000000000ULL /* NAPOT translation */
-#define PTE_RESERVED        0x1FC0000000000000ULL /* Reserved bits */
+#define PTE_RESERVED(svrsw60t59b)    \
+    (svrsw60t59b ? 0x07C0000000000000ULL : 0x1FC0000000000000ULL) /* Reserved bits */
 #define PTE_ATTR            (PTE_N | PTE_PBMT) /* All attributes bits */
 
 /* Page table PPN shift amount */

target/riscv/cpu_cfg_fields.h.inc

@@ -57,6 +57,7 @@ BOOL_FIELD(ext_svadu)
 BOOL_FIELD(ext_svinval)
 BOOL_FIELD(ext_svnapot)
 BOOL_FIELD(ext_svpbmt)
+BOOL_FIELD(ext_svrsw60t59b)
 BOOL_FIELD(ext_svvptc)
 BOOL_FIELD(ext_svukte)
 BOOL_FIELD(ext_zdinx)

target/riscv/cpu_helper.c

@@ -1309,6 +1309,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
     bool svade = riscv_cpu_cfg(env)->ext_svade;
     bool svadu = riscv_cpu_cfg(env)->ext_svadu;
     bool adue = svadu ? env->menvcfg & MENVCFG_ADUE : !svade;
+    bool svrsw60t59b = riscv_cpu_cfg(env)->ext_svrsw60t59b;
 
     if (first_stage && two_stage && env->virt_enabled) {
         pbmte = pbmte && (env->henvcfg & HENVCFG_PBMTE);
@@ -1376,7 +1377,7 @@ static int get_physical_address(CPURISCVState *env, hwaddr *physical,
         if (riscv_cpu_sxl(env) == MXL_RV32) {
             ppn = pte >> PTE_PPN_SHIFT;
         } else {
-            if (pte & PTE_RESERVED) {
+            if (pte & PTE_RESERVED(svrsw60t59b)) {
                 qemu_log_mask(LOG_GUEST_ERROR, "%s: reserved bits set in PTE: "
                               "addr: 0x%" HWADDR_PRIx " pte: 0x" TARGET_FMT_lx "\n",
                               __func__, pte_addr, pte);

target/riscv/tcg/tcg-cpu.c

@@ -839,6 +839,12 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp)
         cpu->cfg.ext_ssctr = false;
     }
 
+    if (cpu->cfg.ext_svrsw60t59b &&
+        (!cpu->cfg.mmu || mcc->def->misa_mxl_max == MXL_RV32)) {
+        error_setg(errp, "svrsw60t59b is not supported on RV32 and MMU-less platforms");
+        return;
+    }
+
     /*
      * Disable isa extensions based on priv spec after we
      * validated and set everything we need.
@@ -1588,6 +1594,8 @@ static void riscv_init_max_cpu_extensions(Object *obj)
 
     if (env->misa_mxl != MXL_RV32) {
         isa_ext_update_enabled(cpu, CPU_CFG_OFFSET(ext_zcf), false);
+    } else {
+        isa_ext_update_enabled(cpu, CPU_CFG_OFFSET(ext_svrsw60t59b), false);
     }
 
     /*