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Re: [PATCH RFC 2/8] target/riscv: Decouple AIA processing from xiselect


From: Jason Chien
Subject: Re: [PATCH RFC 2/8] target/riscv: Decouple AIA processing from xiselect and xireg
Date: Wed, 5 Jun 2024 16:17:43 +0800
User-agent: Mozilla Thunderbird


Atish Patra 於 2024/2/17 上午 08:01 寫道:
From: Kaiwen Xue <kaiwenx@rivosinc.com>

Since xiselect and xireg also will be of use in sxcsrind, AIA should
have its own separated interface when those CSRs are accessed.

Signed-off-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Kaiwen Xue <kaiwenx@rivosinc.com>
---
  target/riscv/csr.c | 147 +++++++++++++++++++++++++++++++++++++--------
  1 file changed, 122 insertions(+), 25 deletions(-)

diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index 8829dee7bc75..1af0c8890a2b 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -287,6 +287,15 @@ static int aia_any32(CPURISCVState *env, int csrno)
      return any32(env, csrno);
  }
+static int sxcsrind_or_aia_any(CPURISCVState *env, int csrno)
Could you rename the function as csrind_or_aia_any() to keep the naming consistency with aia?
+{
+    if (!riscv_cpu_cfg(env)->ext_smaia && !riscv_cpu_cfg(env)->ext_smcsrind) {
+        return RISCV_EXCP_ILLEGAL_INST;
+    }
+
+    return any(env, csrno);
+}
+
  static RISCVException smode(CPURISCVState *env, int csrno)
  {
      if (riscv_has_ext(env, RVS)) {
@@ -323,6 +332,15 @@ static int aia_smode32(CPURISCVState *env, int csrno)
      return smode32(env, csrno);
  }
+static int sxcsrind_or_aia_smode(CPURISCVState *env, int csrno)
Could you rename the function as csrind_or_aia_smode() to keep the naming consistency with aia?
+{
+    if (!riscv_cpu_cfg(env)->ext_ssaia && !riscv_cpu_cfg(env)->ext_sscsrind) {
S-mode CSRs are defined in Smaia and Smcsrind as well. We should ensure at least one of Smaia, Ssaia, Smcsrind, Sscsrind is enabled.
+        return RISCV_EXCP_ILLEGAL_INST;
+    }
+
+    return smode(env, csrno);
+}
+
  static RISCVException hmode(CPURISCVState *env, int csrno)
  {
      if (riscv_has_ext(env, RVH)) {
@@ -342,6 +360,15 @@ static RISCVException hmode32(CPURISCVState *env, int 
csrno)
} +static int sxcsrind_or_aia_hmode(CPURISCVState *env, int csrno)
Could you rename the function as csrind_or_aia_hmode() to keep the naming consistency with aia?
+{
+    if (!riscv_cpu_cfg(env)->ext_ssaia && !riscv_cpu_cfg(env)->ext_sscsrind) {
Hypervisor and VS CSRs are defined in Smaia and Smcsrind as well. We should ensure at least one of Smaia, Ssaia, Smcsrind, Sscsrind is enabled.
+        return RISCV_EXCP_ILLEGAL_INST;
+    }
+
+    return hmode(env, csrno);
+}
+
  static RISCVException umode(CPURISCVState *env, int csrno)
  {
      if (riscv_has_ext(env, RVU)) {
@@ -1804,13 +1831,29 @@ static int aia_xlate_vs_csrno(CPURISCVState *env, int 
csrno)
      };
  }
+static int sxcsrind_xlate_vs_csrno(CPURISCVState *env, int csrno)
Could you rename the function as csrind_xlate_vs_csrno() to keep the naming consistency with aia_xlate_vs_csrno()?
+{
+    if (!env->virt_enabled) {
+        return csrno;
+    }
+
+    switch (csrno) {
+    case CSR_SISELECT:
+        return CSR_VSISELECT;
+    case CSR_SIREG:
+        return CSR_VSIREG;
+    default:
+        return csrno;
+    };
+}
+
  static int rmw_xiselect(CPURISCVState *env, int csrno, target_ulong *val,
                          target_ulong new_val, target_ulong wr_mask)
  {
      target_ulong *iselect;
/* Translate CSR number for VS-mode */
-    csrno = aia_xlate_vs_csrno(env, csrno);
+    csrno = sxcsrind_xlate_vs_csrno(env, csrno);
/* Find the iselect CSR based on CSR number */
      switch (csrno) {
@@ -1839,6 +1882,12 @@ static int rmw_xiselect(CPURISCVState *env, int csrno, 
target_ulong *val,
      return RISCV_EXCP_NONE;
  }
+static bool xiselect_aia_range(target_ulong isel)
+{
+    return (ISELECT_IPRIO0 <= isel && isel <= ISELECT_IPRIO15) ||
+           (ISELECT_IMSIC_FIRST <= isel && isel <= ISELECT_IMSIC_LAST);
+}
+
  static int rmw_iprio(target_ulong xlen,
                       target_ulong iselect, uint8_t *iprio,
                       target_ulong *val, target_ulong new_val,
@@ -1884,44 +1933,44 @@ static int rmw_iprio(target_ulong xlen,
      return 0;
  }
-static int rmw_xireg(CPURISCVState *env, int csrno, target_ulong *val,
-                     target_ulong new_val, target_ulong wr_mask)
+static int rmw_xireg_aia(CPURISCVState *env, int csrno,
+                         target_ulong isel, target_ulong *val,
+                         target_ulong new_val, target_ulong wr_mask)
  {
-    bool virt, isel_reserved;
-    uint8_t *iprio;
+    bool virt = false, isel_reserved = false;
      int ret = -EINVAL;
-    target_ulong priv, isel, vgein;
-
-    /* Translate CSR number for VS-mode */
-    csrno = aia_xlate_vs_csrno(env, csrno);
+    uint8_t *iprio;
+    target_ulong priv, vgein;
- /* Decode register details from CSR number */
-    virt = false;
-    isel_reserved = false;
+    /* VS-mode CSR number passed in has already been translated */
      switch (csrno) {
      case CSR_MIREG:
+        if (!riscv_cpu_cfg(env)->ext_smaia) {
+            goto done;
+        }
          iprio = env->miprio;
-        isel = env->miselect;
          priv = PRV_M;
          break;
      case CSR_SIREG:
-        if (env->priv == PRV_S && env->mvien & MIP_SEIP &&
+        if (!riscv_cpu_cfg(env)->ext_ssaia ||
+            (env->priv == PRV_S && env->mvien & MIP_SEIP &&
              env->siselect >= ISELECT_IMSIC_EIDELIVERY &&
-            env->siselect <= ISELECT_IMSIC_EIE63) {
+            env->siselect <= ISELECT_IMSIC_EIE63)) {
              goto done;
          }
          iprio = env->siprio;
-        isel = env->siselect;
          priv = PRV_S;
          break;
      case CSR_VSIREG:
+        if (!riscv_cpu_cfg(env)->ext_ssaia) {
+            goto done;
+        }
          iprio = env->hviprio;
-        isel = env->vsiselect;
          priv = PRV_S;
          virt = true;
          break;
      default:
-         goto done;
+        goto done;
      };
/* Find the selected guest interrupt file */
@@ -1952,10 +2001,53 @@ static int rmw_xireg(CPURISCVState *env, int csrno, 
target_ulong *val,
      }
done:
+    /*
+     * If AIA is not enabled, illegal instruction exception is always
+     * returned regardless of whether we are in VS-mode or not
+     */
      if (ret) {
          return (env->virt_enabled && virt && !isel_reserved) ?
                 RISCV_EXCP_VIRT_INSTRUCTION_FAULT : RISCV_EXCP_ILLEGAL_INST;
      }
+
+    return RISCV_EXCP_NONE;
+}
+
+static int rmw_xireg(CPURISCVState *env, int csrno, target_ulong *val,
+                     target_ulong new_val, target_ulong wr_mask)
+{
+    bool virt = false;
+    int ret = -EINVAL;
+    target_ulong isel;
+
+    /* Translate CSR number for VS-mode */
+    csrno = sxcsrind_xlate_vs_csrno(env, csrno);
+
+    /* Decode register details from CSR number */
+    switch (csrno) {
+    case CSR_MIREG:
+        isel = env->miselect;
+        break;
+    case CSR_SIREG:
+        isel = env->siselect;
+        break;
+    case CSR_VSIREG:
+        isel = env->vsiselect;
+        virt = true;
+        break;
+    default:
+         goto done;
+    };
+
+    if (xiselect_aia_range(isel)) {
+        return rmw_xireg_aia(env, csrno, isel, val, new_val, wr_mask);
+    }
+
+done:
+    if (ret) {
+        return (env->virt_enabled && virt) ?
+               RISCV_EXCP_VIRT_INSTRUCTION_FAULT : RISCV_EXCP_ILLEGAL_INST;
A virtual instruction exception is raised for attempts from VS-mode or VU-mode to directly access vsiselect or vsireg* in riscv_csrrw_check(), we don't need to check again here.
+    }
      return RISCV_EXCP_NONE;
  }
@@ -4682,8 +4774,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
      [CSR_MIP]      = { "mip",      any,  NULL,    NULL, rmw_mip        },
/* Machine-Level Window to Indirectly Accessed Registers (AIA) */
-    [CSR_MISELECT] = { "miselect", aia_any,   NULL, NULL,    rmw_xiselect },
-    [CSR_MIREG]    = { "mireg",    aia_any,   NULL, NULL,    rmw_xireg },
+    [CSR_MISELECT] = { "miselect", sxcsrind_or_aia_any,   NULL, NULL,
+                       rmw_xiselect                                    },
+    [CSR_MIREG]    = { "mireg",    sxcsrind_or_aia_any,   NULL, NULL,
+                       rmw_xireg                                       },
/* Machine-Level Interrupts (AIA) */
      [CSR_MTOPEI]   = { "mtopei",   aia_any, NULL, NULL, rmw_xtopei },
@@ -4801,8 +4895,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
      [CSR_SATP]     = { "satp",     satp, read_satp,     write_satp     },
/* Supervisor-Level Window to Indirectly Accessed Registers (AIA) */
-    [CSR_SISELECT]   = { "siselect",   aia_smode, NULL, NULL, rmw_xiselect },
-    [CSR_SIREG]      = { "sireg",      aia_smode, NULL, NULL, rmw_xireg },
+    [CSR_SISELECT]   = { "siselect",   sxcsrind_or_aia_smode, NULL, NULL,
+                         rmw_xiselect                                       },
+    [CSR_SIREG]      = { "sireg",      sxcsrind_or_aia_smode, NULL, NULL,
+                         rmw_xireg                                          },
/* Supervisor-Level Interrupts (AIA) */
      [CSR_STOPEI]     = { "stopei",     aia_smode, NULL, NULL, rmw_xtopei },
@@ -4881,9 +4977,10 @@ riscv_csr_operations csr_ops[CSR_TABLE_SIZE] = {
      /*
       * VS-Level Window to Indirectly Accessed Registers (H-extension with AIA)
       */
-    [CSR_VSISELECT]   = { "vsiselect",   aia_hmode, NULL, NULL,
-                          rmw_xiselect                                     },
-    [CSR_VSIREG]      = { "vsireg",      aia_hmode, NULL, NULL, rmw_xireg  },
+    [CSR_VSISELECT]   = { "vsiselect",   sxcsrind_or_aia_hmode, NULL, NULL,
+                          rmw_xiselect                                      },
+    [CSR_VSIREG]      = { "vsireg",      sxcsrind_or_aia_hmode, NULL, NULL,
+                          rmw_xireg                                         },
/* VS-Level Interrupts (H-extension with AIA) */
      [CSR_VSTOPEI]     = { "vstopei",     aia_hmode, NULL, NULL, rmw_xtopei },



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